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8x8 Led Matrix

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This is to certify that the following students

Auti Dinesh (ETRX TE – 4)Yadav Anil (ETRX TE -62)

have successfully completed the synopsis work of project Titled“DOT MATRIX DISPLAY”

------------------------------- ------------------------------INTERNAL EXAMINER EXTERNAL EXAMINER

------------------------------Prof. Sachin Charbe

Internal Guide

---------------------------Prof. Nargis Shaik

Head of department

----------------------------Dr. Varsha Shah


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The basic aim of our project is to present the led matrix in various form of its working, all of which find immense applications. The brain of the system lies well placed in the controller that co-ordinates the total working of the project and controls the minute aspects.It aptly demonstrates the multi faceted nature of the matrix, just by a mere click of the input switch, and the outputs thus obtained are very different from each other. A number of such applications can be in built into this device with no change in its efficiency. Along with , it provides adequate clarity and a fine tuning between brightness and contrast which proves pleasant for the eyes as well. Not to forget its energy efficient working that serves as an icing over the cake. Other possible enhancements would be using SMD led' s that are efficiently packed having adjustable contrast and more energy efficient nature than normal led' s, yet bright enough to capture your attention.

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It is With great pleasure that we are submitting this report on“Dot Matrix Display”.

As in case project, we faced many problems while giving shape toour ideas and making the project mould into reality.

We take this opportunity to express our sense of gratitude towardsour internal guide Prof. Sachin Charbe for his valuable suggestions and guidance from time to time.

We are also thankful to the head of department, Prof. Nargis Shaikand the remaining staff for making facilities available and giving their support and guidance.

Although we have not mentioned each name, we would like to saythat we appreciate every individual who was associated with our projectand made experience satisfying and fulfilling one.

Auti Dinesh Yadav Anil

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Table of contents

Title...................................................................................................................1 Abstract …........................................................................................................3

Acknowledgement ….......................................................................................4

1. Introduction ….......................................................................................8

2. Schematic2.1 Single Colour Matrix(Single Sided Board) …......................102.2 Dual Colour Matrix(Double Sided Board) ….......................11

3. Operation 3.1 Dev Board …........................................................................13 3.2 Matrix …................................................................................14 3.3 Final Board (©MATRIX V1.2) ….........................................16

4. Component List ….................................................................................20

5. Board Layout5.1Single Colour Matrix(Single Sided Board) …..................................225.2Dual Colour Matrix(Double Sided Board – Top Layer) …..............225.3Dual Colour Matrix(Double Sided Board – Bottom Layer) ….......235.4Dual Colour Matrix(Double Sided Board – Top & Bottom Layer)..23

6. Programming

6.1 Program ….............................................................................25 6.2 Hex Code …............................................................................23

7. Easily Applicable Graphical Layout Editor7.1 EAGLE Product Information …............................................377.2 Schematic Editor …...............................................................377.3 Auto-router …........................................................................387.4 CAM Processor ….................................................................387.5 EAGLE CAD Design Rules …..............................................39

8. Application and Future Scope …..............................................................43

9. Conclusion …...........................................................................................47

10. PCB Making Process10.1 Artwork Generation …..........................................................49

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10.2 Photoresist PCB Laminates …..............................................5110.3 Exposure …...........................................................................5110.4 Developing ….......................................................................5310.5 Etching ….............................................................................5410.6 Tin Plating …........................................................................5510.7 Drilling ….............................................................................5610.8 Cutting ….............................................................................5810.9 Through – Plating …............................................................5910.10 Through – Plating Using Rivets ….......................................61

11. References ….....................................................................................62

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1.Introduction Electronics is not just a field of study, it is a foundation pillar of the modern day technological advancements. After thinking a lot on above lines we finally decided to work on a device which is not just versatile in its functioning but also is the next step that the world is taking towards a highly energy efficient future. This project gives a detailed information on the basic structural anatomy of LED matrix and the wide interaction that is possible, owing to the ease with which it can be interfaced with a controller and can be used as a output device in embedded systems, in which power and space are areas of major concern especially when it comes to implementing them in consumer products Keeping a specific goal in mind, we travelled on the same lines , which is efficiently presented in the pages to be follow. Finally, having accomplished our aim, we concluded by throwing light on the modern day innovation of LED TV.

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2. Schematic

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2.1 Single Colour Matrix(Single Sided Board)

Matrix V1.1

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2.2 Dual Colour Matrix(Double Sided Board)

Schematic: MATRIX V1.2

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3. Operation

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3.1 Dev Board

The Dev Board or Development Board is very essential for experimenting with microcontrollers. Development is not easy if you use bread board or vero board. After some time wires will become loose and establishing a large circuit on vero board is too tedious. To solve this problem we decided to make our own low cost Dev Board which has following specifications

• Low cost.• All basic connection for developing application with AVR MCU's.• In circuit programmable with USB AVR Programmer. • Supports 40 pin MCU's like Atmega16,ATmega32 and Atmega8535.• Can be further extended for use with LCD,DOT MATRIX etc interfacing.

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3.2 Matrix

An LED Matrix is an array of LED's with the anode or positive terminal of each row connected together, and the cathode or negative terminal of each column connected together. Or the anode can be connected to a column, and cathode connected to a row.

They come in various sizes, colors and formats.The most common sizes are 5x7, 5x8 and 8x8 displays. This means that, for example, a 5x8 display would have 5 columns with 8 rows of LED's.

The most common colors are red, green and yellow. There are also two and three colored versions, with the different colored LED's sharing a common pin in each row or column and a seperate pin for the corresponding column or row. This allows each color to be turned on or off individually. When there are two or more colors, the LED's will share a common anode or cathode (positive or negative respectively). Lets examine more closely the actual layout of a LED matrix Here we see that each row connects to that rows cathode or negative leg of the

5x7 Matrix 8x8 Matrix

Internal Structure of 8x8 Matrix

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LED's. Correspondingly, each column connects the anode or positive leg together. Please not that a LED matrix can also be the other way around.

To control a LED matrix, we have two options:

• Cycle through each row, turning on the LED's in that row as needed• Cycle through each column, turning on the LED's in that column as needed

It is not possible to control the LED matrix all at once, as all the individual LED's share both their inputs. The way around this is to use Persistance of Vision. By cycling through each row or column quite fast (~50Hz and above) you should not see any flicker, and instead see the whole LED matrix display as if it was all working at once. If we were to choose the first of the two options, we would first ground the first row connection (connection ROW1) and leave the remaining ROWX connections floating or high.

Matrix Internal Structure

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Then, we would pull each column connection high if we wanted that LED to turn on, or leave it floating or low to keep it off. For example if we wanted to turn on LED3 and LED5, then with the ROW1 connection pulled low, we would leave COL1, COL2 and COL4 floating or low, and pull COL3 and COL5 high.Then after leaving ROW1's displayed LED's on for a set period of time, we would pull ROW1 high or floating and pull ROW2 low. At the same time, we would pull the corresponding column connections high to turn on the individual LED's in that row.

3.3 Final Board

LEDs in the same column have the anodes on a common line, running top to bottom. Similarly for LEDs in a single row have cathodes on a common line, running left to right. This means that if on the wires that make up the column an 8 bit pattern say 10111110 is set and then the common line for some row is grounded, then the LEDs in that particular row will glow as dictated by this bit-pattern. With this bit-pattern, for example, if you ground the common line for the topmost row then the LED1 and LED7 will be OFF and rest in that row will be ON. You may ground the common line on any row and the bit-pattern set on the column wires will appear as glowing LEDs in that particular row.

This design, however, is not the complete solution. The reason is that different rows cannot display different bit patterns. They will all display the same pattern that has been set on the column wires, once they are grounded. In order to overcome this problem, we shall use a clever trick - persistence of vision. The idea is that if changes are made in rapid succession, the human eye is unable to sense the small incrementals and perceives the event as smooth continuous motion. In practice we display one row at a time - we set the bit pattern on the column for the topmost row and ground that row keeping all other rows un-grounded. Next, we set the bit pattern for the second row on the column wires and then ground the second row, keeping all other rows un-grounded and so on till we have displayed all the rows, one at a time, in succession from top to bottom. We repeat the same process over and over again, just like scan-lines in a TV. We make the switching between the rows so fast that it appears that you are viewing the entire LED matrix in one go.

Matrix Internal Structure - Row 1

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Now we can attach the 8x8 LED module shown above to two different ports - one to set bit patterns for the column wires and other to ground different rows when desired. In the following figure PORTC is used to set patterns on column wires and PORTA is used to ground rows:

This type of connection has some drawbacks too. The thing is when a row is grounded then current from all the LEDs that are ON in that row sinks collectively at this pin and this may be dangerous for the microcontroller. That's where the driver IC shown in the figure on the top comes into picture. We use ULN2803 to sink the current safely from all 8 rows. The ULN2803 IC is shown below:

Pin 9 is connected to ground. Pins 1-8 are connected to the PORTA[0:7] which we


ULN 2803

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use to control the selective sinking of the rows. The row [1:8] wires are connected to pins [18:11] so that when PORTA PIN0 is set ON, the row 1 is connected to the ground. So keeping these factors in mind, the block diagram can be modified as:

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4. Component List

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4. Component List

Component name Quantity Price(Rs.)Atmega16 1 130ULN2803 1 15AVR ISP Header 1 15RF Cable 1 107805T 1 81N4007 1 2DIP Switches 8 24Led 1 2Resistor - 330 ohm 1k ohm



Sliding Switch 1 3Crystal 1 7Capacitors- 22pF 100uF 0.1uF



Power Jack 1 5Round Pin socket- 40pin18pin 1



Double side copper clad epoxy

1 170

Screw and nuts 4 15Total 444

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5. Board

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5.1 Single Layer Board Layout

5.2 Dual Colour Matrix (Top Layer)

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5.3 Dual Colour Matrix (Bottom Layer)

5.4 Dual Colour Matrix(Top & Bottom Layer)

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6. Programming

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6.1 Program

1. #include <avr/io.h>2. #include<util/delay.h>3. int y;4. unsigned char d[8]={1,2,4,8,16,32,64,128};5. unsigned char s2c[4]={0X3C,0X24,0X24,0X3C} ;6. unsigned char s3c[6]={0X7E,0X42,0X42,0X42,0X42,0X7E};7. unsigned char s4c[8]={0XFF,0X81,0X81,0X81,0X81,0X81,0X81,0XFF};8. unsigned char s5c[8]={0XFF,0XC1,0XA1,0X91,0X89,0X85,0X83,0XFF};9. unsigned char s6c[8]={0XFF,0X83,0X85,0X89,0X91,0XA1,0XC1,0XFF};10.unsigned char s7c[8]={0XFF,0XC3,0XA5,0X99,0X99,0XA5,0XC3,0XFF};11.unsigned char w[8]={0x81,0x81,0x81,0x81,0x81,0x99,0XA5,0XC3};12.unsigned char lc[8]={0x80,0X80,0X80,0X80,0X80,0X80,0X80,0XFF};13.int move(int m,int n,int o,int p,int q,int r,int s,int t,int loop)14.{15.int a=0;16.int count;17.if(loop==1)18.{19.count=4000;20.}21.else22.{23.count=10000;24.}25.label:26.PORTC=m;27.PORTD=1;28.RESET();29.PORTC=n;30.PORTD=2;31.RESET();32.PORTC=o;33.PORTD=4;34.RESET();35.PORTC=p;36.PORTD=8;37.RESET();38.PORTC=q;39.PORTD=16;40.RESET();41.PORTC=r;42.PORTD=32;43.RESET();

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44.PORTC=s;45.PORTD=64;46.RESET();47.PORTC=t;48.PORTD=128;49.RESET();50.a++;51.if(a>=count)52.{53.a=0;54.if (loop==1)55.{56.if((m<=128)||(n<=128)||(o<=128)||(p<=128)||(q<=128)||(r<=128)||(s<=128)||

(t<=128))57.{58.m*=2;59.n*=2;60.o*=2;61.p*=2;62.q*=2;63.r*=2;64.s*=2;65.t*=2;66.}67.else68.{69.goto label2;70.}71.}72.else73.{74.goto label2;75.}76.}77.goto label;78.label2:return(0);79.}80.void RESET(void)81.{82.PORTD=0;83.PORTC=0;84.PORTA=128;85.}86.int wait(int a)87.{

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88.label: if (a==y) 89.{90.a=PINA;91. goto label;92. }93. }94. int main (void)95. {96. DDRC=0XFF;97. DDRD=0XFF;98. DDRA=0X00;99. PORTA=0XFF;100. int j,i=0;101. int k=0;102. int u=0;103. while(1)104. {105. PORTD=0XFF;106. PORTC=0XFF;107. y=PINA;108. if(y==0XEF)109. {110. wait(y);111. PORTC=0X01;112. PORTD=0X01;113.114. while (1)115. {116.117. y=PINA;118. if(y==0XFE) 119. { 120. wait (y);121. u++;122. if(PORTD>=2)123. {PORTD= PORTD/2;124. _delay_ms(100);125. }126. else 127. {128. PORTD=1; 129. _delay_ms(100);130. }131. } 132.

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133.134.135. if(y==0XFD) 136. { 137. wait(y);138. u++;139. if(PORTC<=64)140. {PORTC=PORTC*2;141. _delay_ms(100); 142. }143. else144. {145. PORTC=128;146. _delay_ms(100); 147. } 148. } if(y==0XFB) 153. { 154. wait(y);155. u++;156. if(PORTC>=2)157. {158. PORTC=PORTC/2;159. _delay_ms(100); 160. }161. else162. {163. PORTC=1;164. _delay_ms(100);165. }166.167. } if(y==0XF7) 172. {173. wait(y);174. u++;175. if(PORTD<=64)176. {PORTD=PORTD*2;177. _delay_ms(100);

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178. }179. else180. {181. PORTD=128;182. _delay_ms(100);183. }184.185. }186. if ((PORTD==0X01)&&(PORTC==0X10))187. {188. if (u>15)189. {190. lose:191. for(j=0,i=0;j<8,i<8;i++,j++)192. {193. PORTC=lc[i];194. PORTD=d[j];195. RESET();196. }197. goto lose;198. }199.200.201. else if(u<=15)202. {203. won:204. for(j=0,i=0;j<8,i<8;i++,j++)205. {206. PORTC=w[i];207. PORTD=d[j];208. RESET();209. }210. goto won;211. }212. }213.214.215. }216. }217.218. if(y==0XDF)219. {220. wait(y);221. while(1)222. {

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223. int temp;224. temp=move(0X18,0X24,0X42,0X81,0XFF,0X81,0X81,0X81,0);225. temp=move(0X81,0XC1,0XA1,0X91,0X89,0X85,0X83,0X81,0);226. temp=move(0XFF,0X18,0X18,0X18,0X18,0X18,0X18,0XFF,0);227. temp=move(0x80,0X80,0X80,0X80,0X80,0X80,0X80,0XFF,0);228. }229. }230. if(y==0XBF)231. {232. wait(y);233. while(1)234. {235. A:PORTC=0X18;236. PORTD=0X18;237. if(k>=4000)238. {k=0;239. goto N;240. }241. k++;242. goto A;243. N:for(j=2,i=0;j<6,i<3;i++,j++)244. {245. PORTC=s2c[i];246. PORTD=d[j];247. RESET();248. }249. if(k>=3000)250. {k=0;251. goto I;252. }253. k++;254. goto N;255. I:for(j=1,i=0;j<7,i<6;i++,j++)256. {257. PORTC=s3c[i];258. PORTD=d[j];259. RESET();260. }261. if(k>=3000)262. {k=0;263. goto L;264. }265. k++;266. goto I;267. L:for(j=0,i=0;j<8,i<8;i++,j++)

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268. {269. PORTC=s4c[i];270. PORTD=d[j];271. RESET();272. }273.274. if(k>=3000)275. {k=0;276. goto Y;277. }278. k++;279. goto L;280. Y:for(j=0,i=0;j<8,i<8;i++,j++)281. {282. PORTC=s5c[i];283. PORTD=d[j];284. RESET();285. }286. if(k>=3000)287. {k=0;288. goto D;289. }290. k++;291. goto Y;292. D:for(j=0,i=0;j<8,i<8;i++,j++)293. {294. PORTC=s6c[i];295. PORTD=d[j];296. RESET();297. }298. if(k>=3000)299. {k=0;300. goto V;301. }302. k++;303. goto D;304. V:for(j=0,i=0;j<8,i<8;i++,j++)305. {306. PORTC=s7c[i];307. PORTD=d[j];308. RESET();309. }310. if(k>=3000)311. {k=0;312. goto A;

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313. }314. k++;315. goto V;316.317. }318. }319. if(y==0X7F)320. {321. wait(y);322. while(1)323. {324. int z;325. z=move(0X04,0X0A,0X11,0X1F,0X11,0X11,0X11,0X11,1);326. z=move(0X11,0X11,0X19,0X15,0X13,0X11,0X11,0X11,1);327. z=move(0X1F,0X04,0X04,0X04,0X04,0X04,0X04,0X1F,1);328. z=move(0X10,0X10,0X10,0X10,0X10,0X10,0X10,0X1F,1);329. }330. }331. }332. }

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6.2 Hex code

1. :1000000014C02EC02DC02CC02BC02AC029C028C0AF2. :1000100027C026C025C024C023C022C021C020C0C43. :100020001FC01EC01DC01CC01BC011241FBECFE5B94. :10003000D2E0DEBFCDBF10E0A0E6B0E0E0E4F6E0455. :1000400002C005900D92A23AB107D9F710E0A2EADA6. :10005000B0E001C01D92A43AB107E1F7B3D0EEC2FF7. :10006000CFCF2F923F924F925F926F927F928F925B8. :100070009F92AF92BF92CF92DF92EF92FF920F93379. :100080001F93DF93CF93CDB7DEB73401B1E08B166A10.:10009000910429F0F0E18F2EF7E29F2E04C0E0EAF011.:1000A0008E2EEFE09E2EA0E8B4E02B2EF8E03F2E3F12.:1000B000E0E14E2EB0E25B2EE0E0F0E085BBB1E08713.:1000C000B2BB12BA15BAABBB65BBB2E0B2BB12BAD714.:1000D00015BAABBB45BB22BA12BA15BAABBB25BB2E15.:1000E00032BA12BA15BAABBB05BB42BA12BA15BACC16.:1000F000ABBBE5BA52BA12BA15BAABBBC5BAB0E4DB17.:10010000B2BB12BA15BAABBBA5BAA2BB12BA15BA2A18.:10011000ABBB3196E815F9058CF2E1E06E1671047F19.:1001200061F581389105C4F061387105ACF041385220.:10013000510594F0213831057CF00138110564F04721.:10014000B1E8EB16F10444F0E1E8CE16D10424F05622.:10015000B1E8AB16B1048CF4880F991F660F771FB623.:10016000440F551F220F331F000F111FEE0CFF1CF124.:10017000CC0CDD1CAA0CBB1C9FCF80E090E0CF918325.:10018000DF911F910F91FF90EF90DF90CF90BF908426.:10019000AF909F908F907F906F905F904F903F902727.:1001A0002F90089512BA15BA80E88BBB089520915C28.:1001B000A2003091A3008217930719F489B390E04D29.:1001C000FACF08958F929F92AF92BF92CF92DF921330.:1001D000EF92FF920F931F938FEF84BB81BB1ABAEC31.:1001E0008BBB2FEF22BB25BB89B390E08F3E9105DF32.:1001F00009F0B0C09093A3008093A20089B38F3E1233.:10020000E9F381E085BB82BB20E030E0F1E048EA2134.:1002100051E6E0E889B3682F70E06E3F710599F40C35.:1002200089B38E3FE9F32F5F3F4F82B3823038F0BE36.:1002300082B3869582BBCA010197F1F729C0F2BB5037.:10024000CA010197F1F76D3F710589F489B38D3FBC38.:10025000E9F32F5F3F4F85B3813428F485B390E0F539.:10026000880F991F11C0E5BBCA010197F1F76B3FD940.:10027000710571F489B38B3FE9F32F5F3F4F85B36D41.:10028000823020F085B3869585BB14C0F5BB12C0C342.:10029000673F710591F489B3873FE9F32F5F3F4FC343.:1002A00082B3813430F482B390E0880F991F82BB0F

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89.:100580002830310571F72BE0483B520709F44ACF7890.:100590004F5F5F4FE4CF8F37910509F023CE9093E391.:1005A000A3008093A20089B38F37E9F384E090E04192.:1005B0006AE070E041E150E02FE130E001E110E05D93.:1005C000A1E1EA2EF12CF1E1CF2ED12CE1E1AE2E0A94.:1005D000B12CB1E08B2E912C44DD81E190E061E10295.:1005E00070E049E150E025E130E003E110E039DD6196.:1005F0008FE190E064E070E044E050E024E030E01F97.:1006000004E010E0A4E0EA2EF12CF4E0CF2ED12C8F98.:10061000EFE1AE2EB12C25DD80E190E060E170E0ED99.:1006200040E150E020E130E000E110E0B0E1EB2EED100. :10063000F12CA0E1CA2ED12C14DDB8CFF894FFCF55101. :1006400001020408102040803C24243C7E424242A7102. :10065000427EFF818181818181FFFFC1A1918985D6103. :1006600083FFFF83858991A1C1FFFFC3A59999A548104. :10067000C3FF818181818199A5C380808080808032105. :0206800080FFF9106. :00000001FF

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7. Easily Applicable Graphical Layout Editor

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7.1 EAGLE Product Information

The EAGLE Layout Editor is an easy to use, yet powerful tool for designing printed circuit boards (PCBs). The name EAGLE is an acronym, which stands for

Easily Applicable Graphical Layout EditorThe program consists of three main modules

• Layout Editor • Schematic Editor • Autorouter

which are embedded in a single user interface. Therefore there is no need for converting netlists between schematics and layouts.Program Features (Professional Edition)

General• online Forward- and Back-Annotation• context sensitive help function• no hardware copy protection!• multiple windows for board, schematic and library• powerful User Language• integrated text editor• available for Windows, Linux and Mac

Layout Editor• maximum drawing area 1.6 x 1.6m (64 x 64 inch)• resolution 1/10,000mm (0.1 micron)• up to 16 signal layers• conventional and SMT parts• comes with a full set of part libraries• easily create your own parts with the fully integrated library editor• undo/redo function for ANY editing command, to any depth• script files for batch command execution• copper pouring• cut and paste function for copying entire sections of a drawing• design rule check• interactive Follow-me Router (requires the Autorouter module)

7.2 Schematic Editor• up to 999 sheets in one schematic• electrical rule check

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• gate and pinswap• create a board from a schematic with a single command

7.3 Autorouter• ripup&retry router• up to 16 signal layers• routing strategy driven by user definable cost factors

7.4 CAM Processor• Postscript• pen plotters• Gerber plotters• Excellon and Sieb&Meyer drill files• configurable through ASCII file for easy definition of your own output devices

System Requirements

Windows• Windows 2000, Windows XP, Windows Vista or Windows 7

Linux• Intel PC based Linux• Kernel version 2.6• X11 in at least 8bpp mode

Mac• Mac OS X 10.4 on PPC or Intel

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7.5 Eagle CAD Design Rule

1. description[de] = <b>EAGLE Design Rules</b>\n<p>\nDie Standard-Design-Rules sind so gewählt, dass sie für \ndie meisten Anwendungen passen. Sollte ihre Platine \nbesondere Anforderungen haben, treffen Sie die erforderlichen\nEinstellungen hier und speichern die Design Rules unter \neinem neuen Namen ab.

2. description[en] = <b>EAGLE Design Rules</b>\n<p>\nThe default Design Rules have been set to cover\na wide range of applications. Your particular design\nmay have different requirements, so please make the\nnecessary adjustments and save your customized\ndesign rules under a new name.

3. layerSetup = (1*16)4. mtCopper = 0.035mm 0.035mm 0.035mm 0.035mm 0.035mm 0.035mm

0.035mm 0.035mm 0.035mm 0.035mm 0.035mm 0.035mm 0.035mm 0.035mm 0.035mm 0.035mm

5. mtIsolate = 1.5mm 0.15mm 0.2mm 0.15mm 0.2mm 0.15mm 0.2mm 0.15mm 0.2mm 0.15mm 0.2mm 0.15mm 0.2mm 0.15mm 0.2mm

6. mdWireWire = 8mil7. mdWirePad = 8mil8. mdWireVia = 8mil9. mdPadPad = 8mil10.mdPadVia = 8mil11.mdViaVia = 8mil12.mdSmdPad = 8mil13.mdSmdVia = 8mil14.mdSmdSmd = 8mil15.mdViaViaSameLayer = 8mil16.mnLayersViaInSmd = 217.mdCopperDimension = 40mil18.mdDrill = 8mil19.mdSmdStop = 0mil20.msWidth = 10mil21.msDrill = 24mil22.msMicroVia = 9.99mm23.msBlindViaRatio = 0.50000024.rvPadTop = 0.25000025.rvPadInner = 0.25000026.rvPadBottom = 0.25000027.rvViaOuter = 0.25000028.rvViaInner = 0.25000029.rvMicroViaOuter = 0.25000030.rvMicroViaInner = 0.25000031.rlMinPadTop = 10mil

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32.rlMaxPadTop = 20mil33.rlMinPadInner = 10mil34.rlMaxPadInner = 20mil35.rlMinPadBottom = 10mil36.rlMaxPadBottom = 20mil37.rlMinViaOuter = 8mil38.rlMaxViaOuter = 20mil39.rlMinViaInner = 8mil40.rlMaxViaInner = 20mil41.rlMinMicroViaOuter = 4mil42.rlMaxMicroViaOuter = 20mil43.rlMinMicroViaInner = 4mil44.rlMaxMicroViaInner = 20mil45.psTop = -146.psBottom = -147.psFirst = -148.psElongationLong = 10049.psElongationOffset = 10050.mvStopFrame = 1.00000051.mvCreamFrame = 0.00000052.mlMinStopFrame = 4mil53.mlMaxStopFrame = 4mil54.mlMinCreamFrame = 0mil55.mlMaxCreamFrame = 0mil56.mlViaStopLimit = 0mil57.srRoundness = 0.00000058.srMinRoundness = 0mil59.srMaxRoundness = 0mil60.slThermalGap = 0.50000061.slMinThermalGap = 20mil62.slMaxThermalGap = 100mil63.slAnnulusIsolate = 20mil64.slThermalIsolate = 10mil65.slAnnulusRestring = 066.slThermalRestring = 167.slThermalsForVias = 068.checkGrid = 069.checkAngle = 070.checkFont = 171.checkRestrict = 172.useDiameter = 1373.maxErrors = 00

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8. Application and Future Scope

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8. Application and Future Scope LEDs are the light source in solar powered products. In order to understand what advantages the LED offers over incandescent lights, we must first understand how the LED works. A light emitting diode is composed of a semiconductor diode. A semiconductor is a material that can conduct electricity. A semiconductor diode is composed of a semiconductive crystal that has added impurities in order to create a positive and negative side; since current flows in one direction through the diode. A region is then created in between the positive and negative zones, called a PN junction, which is where the action takes place within the diode; in our case it emits light.Incandescent lights, on the other hand, operate on a different principle. Current is sent through a filament. The filament resists the flow of electrons through it, which causes the filament to generate heat. The radiated heat produces a visible light.So what then are the advantages?- Efficiency: An incandescent light requires much more energy to properly heat the filament in order to generate light. The light produced by an LED is a cool light. More light is produced per watt in an LED than an incandescent. Even more energy can be saved if the light is solar powered.-Color: LEDs do not require filters, like colored bulbs, in order to create a specific colored light. Color is produced based on the material of the semiconductor.-Size: LEDs come in many different sizes since they are not constrained to creating a vacuum in which to house the filament. LEDs can be smaller than 2 mm.-On/Off Time: An LED takes only microseconds to achieve its full brightness. This is ideal in a solar powered light that is running off of a battery that has determinate energy life.-Cycling: In applications that are cycled between on and off frequently, like an outdoor solar light, LEDs are ideal since they won't burn out quickly.-Lifetime: The lifetime of the LED greatly exceeds its incandescent, and even its fluorescent counterparts. An average lifetime of an incandescent light is 1,000-2,000 hours and a fluorescent bulb is 10,000-15,000 hours. The LED, on the other hand, has a typical lifetime of 35,000-50,000 hours.-Light Dispersement: An LED is designed to focus its light, so where an incandescent or fluorescent may seem brighter since the light radiates in all directions, the LED light can be directed to a specific location without the use of an external reflector.-Ecologically Friendly: LEDs are more efficient than others, as stated above; so they conserve electricity, especially if they are solar powered. LEDs do not contain toxic chemicals like fluorescent bulbs do. Several incandescent and fluorescent bulbs will be used during the lifetime of a single LED. If your desire is to light a space and save the environment, then the clear choice is the LED. Solar powered LEDs are an additional benefit in that they require no additional energy costs

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LED TV Buying a TV has become as complicated as selecting the right mobile phone plan. Before large flat panel displays invaded our lives, the only real question when purchasing a CRT (cathode ray tube) TV was how big did you want it and how much space did you have in your room to house it? Sure, there were some quality issues but mostly it was dictated by how many diagonal inches you could get for your buck. While some of that justification still rings true with today’s TVs, now there’s the issue of plasma versus LCD to contend with, and just when you had that sorted out, LED TVs have entered the arena as an option. However, there still seems to be a fair bit of confusion surrounding what exactly an LED TV is. Well, basically, it’s another form of LCD TV that uses LEDs to provide its light source.All LCD TVs are backlit because LCDs are a transmissive type of display technology, which means they don’t produce their own light. So for an LCD television to produce an image on the flat panel display, its pixels have to be backlit by a separate lighting source. Currently, most LCD TVs used CCFL technology (cold cathode fluorescent lamps) as their backlight source. They deliver good colors and brightness, and decent contrast, but not great blacks – the domain of the plasma TV. But TVs utilizing brighter LED backlighting can achieve much better blacks, as well as brighter colors and even greater contrast ratios (Toshiba Regza 55X1 is boasting 5,000,000:1). NB: Contrast is measured from the darkest lit area of the screen to the brightest area to give a ratio.

But just in case you thought your selection choice was now made easy, there are a couple of LED options – full matrix LED and edge lit LED TVs. Let’s go through the differences and look at what some of the manufacturers are using as their preferred backlighting choice.

Clarification: is it really an LED TV?A true LED TV is one of those giant screens you usually see at outdoor stadiums, at grand prix events and rock venues. They are large screens made up of thousands of extremely bright LED lights. But because the size of LEDs are mostly too big and chunky to use in TVs, but they are an ideally suited as a light source for backlighting LCD crystals.

How LED technology is used in LCD TVsEdge lighting

Edge lighting is pretty much as described. In this method, a series of LED backlights are positioned along the outside edges of the screen. From there, the light is dispersed across the screen, which means the LED/LCD TV can be made very thin. And while the results may be better than CCFL screens, the black levels in edge lighting are not

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as deep and, if you look closely, the edge area of the screen tends to be brighter than the middle viewing area.

Full-array backlightingTo take full advantage of LED lighting, some manufacturers use full-array LED backlighting, where many rows of LEDs are placed behind the entire surface of the screen. Although this makes for a thicker TV panel, the LEDs provide more even, brighter colors and greater contrast. A measurable benefit of full-array lighting can be seen when "local dimming" is utilized, meaning that each LED (or more common, a selected “zone” of LEDs) can be turned on and off independently within the screen, thus providing greater control of the brightness and darkness for each of those areas. Greater contrast levels are achieved by diminishing the effects of light from brightly lit neighboring areas seeping into blackened areas of the screen, which is one of the downsides of LCD screens.

In other words, the greater level of dimming control, the better the picture quality.

A number of manufacturers are preferring this technology with impressive results. They include: Samsung, Toshiba, LG and Metz.

Speaking of quality, currently, most LED backlighting is provided by white LEDs that are plentiful and cost less than their red, green, blue (RGB) cousins. But as popularity and demand increase, and research continues to improve, expect to see RGB LEDs, that provide a much greater color gamut and therefore much richer, denser and varied colors, being incorporated into TVs. Already a couple of manufacturers including Sony and Sharp have models with RGB LEDs.

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Features of LED backlit LCD TVs

• An LED TV achieves deeper blacks as well as emitting brighter images, thereby producing better contrast ratios;

• They are slimmer (especially edge-LED lighting systems);• They deliver better viewing angles than other LCD TVs;• LEDs are long-lasting;• LEDs are more energy efficient than their CCFL counterparts, and better than

plasma Tvs and much better than CRTs;• LEDs don’t use mercury like some other backlighting methods.

Then there’s Mitsubishi's Laser TV and Sony, Phillips and others will have 3-D TVs on the market from next year. Give it some more time and we'll also have holographic TV added to the mix. It’s like I said, choosing a TV will be as easy as choosing a mobile phone plan – and don’t expect it to get any easier in the near future.

Some of the other prominent applications

A digital LED clock seems to be the most widely used LED application and the most cheapest, most durable, and long lasting (battery life). It mainly consists of a controller a matrix of LED's which acts as a screen ( which displays the time ) and a power source ( battery ). Since the power consumption of LED is very low compared to other display devices the clock works for longer time more efficiently and hence the durability of the product is improved.

Scrolling displays are seen almost everywhere, the best example would be in public transport. This is a fine application since in public transport using LCD's would not prove fruitful and would cause many problems. But LED displays mounted in a bus or a train serve as a dual purpose as in they consume very low power so battery life has improved and LED's are brighter than LCD's so that it can be clearly viewed from long distances.

It will be interesting to see what developments are coming for more residential applications of LED lights. LED lighting technology has been researched and developed for the past two decades and we are beginning to see practical applications from this work. There is already wide spread use of LED traffic signs and LED headlights where a premium is placed on a reliable light source that is cheaper and less labor intensive to maintain. We in the industry are certain that tomorrows LED lights will last longer and consume even less power than todays energy efficient led light bulbs. LED lighting will be used to replace virtually every type of light, bulb, and lamp that is currently in use. So the future with LED's seems to be more promising and energy efficient.

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The project on LED matrix that we have worked on has attempted to explore the various facilities that this device offers. We have made a practical study of the various programs , which once fed to the controller that forms the heart of the system, that give profound results on execution. While doing so, we went through several developmental stages, which we have thoroughly demonstrated and explained in this project. First we performed all the experiments on the single coloured matrix, to the point of our satisfaction and then ultimately, we upgraded the system to the use of multi coloured matrix, to the fullest of its capacity and did further work on it. The result of all the work on this device, is the extravagant ©MATRIX V1.2 that is presented by us, which is not only functioning exceedingly well, but is also packaged in such a way that it can be viewed as a final product that is now ready for sale!!

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10. PCB Making Process

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10.1 Artwork Generation

You need to generate a positive (i.e. black = coppper) UV translucent artwork film You'll never get a good board without good artwork, so it is important to get the best possible quality at this stage.The most important thing is to get a clear sharp image with a very solid opaque black. Nowadays, artwork will almost always be drawn using either a dedicated PCB CAD program, or a suitable drawing / graphics package. The merits of various software packages will not be discussed here, other than to say that it is absolutely essential that your PCB software prints holes in the middle of pads, to act as centre-marks when drilling. It is virtually impossible to accurately hand-drill boards without these holes. If you're looking to buy PCB software at any cost level, and want to be able to do hand-prototyping of boards before production, check that this facility is available. If you're using a general purpose CAD or graphic package, define pads as either a grouped object containing a black filled circle with a smaller concentric white filled circle on top of it, or as an unfilled circle with a thick black line style (i.e. a black ring). When defining pad and line shapes, the following minimum sizes are recommended for reliable results: The artwork must be printed such that the printed side will be in contact with the PCB surface when UV exposing, to avoid blurred edges. In practice this means that if you design the board as seen from the component side, the bottom (solder side) layer should be printed the 'correct' way round, and the top side of a double-sided board must be printed mirrored. Artwork quality is very dependant on both the output device and the media used, both of which will now be discussed.Media Contrary to what you may think, it is NOT necessary to use a transparent artwork medium - as long as it is reasonably translucent to UV, it's fine - less translucent materials may need a slightly longer exposure time. Line definition, black opaqueness and toner/ink retention are much more important. Possible print media include the following:Clear acetate OHP transparencies - these may seem like the most obvious candidate, but are expensive, tend to crinkle or distort from laser printer heating, and toner/ink can crack off or get scratched very easily.NOT recommended.Polyester drafting film is good but expensive, the rough surface holds ink or toner well, and it has good dimensional stability. If used in a laser printer, use the thickest stuff you can get, as the thinner film tends to crinkle too much due to the fusing heat. Even thick film can distort slightly with some laser printers.Not especially recommended, but adequate....and the winner is....

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Tracing paper Get the thickest you can find - at least 90gsm (thinner stuff can crinkle), 120gsm is even better but harder to find. It's cheap, easily available from office or art suppliers (usually in pads the same size as normal paper sizes), has good enough UV translucency and is nearly as good as drafting film for toner retention, and stays flatter under laser-printer heat than polyester or acetate film. The stuff I use is a "Gateway Tracing", 90GSM A4 pad made by Royal Sovereign, code RS442715. Viking Direct order code Q29-RG1059Output devicesInk-jet printers - Not tried them myself, but I hear very mixed reports from "perfect" to "useless"! The main problem will be getting an opaque enough black. They are so cheap that it's certainly worth a try, and with as many different media types as you can find, but don't expect the same quality you can get from lasers. It may also be worth trying an inkjet print onto paper, which can then be photocopied onto tracing paper with a good quality photocopier. I have had good reports from several people using tracing paper with HP Deskjets, but my Epson Stylus Photo750 inkjet is useless on tracing paper.

If you plot largish ground planes directly from inkjet, both 90gsm and 112gsm tracing papers crinkle slightly in these areas (the 90 more than the 112). I find that the best procedure is to allow the inkjet plot to dry thoroughly (on an HP Deskjet 670C or 895CXi set to normal - best print quality is not necessary) and then flatten out the plot under a clean sheet of paper placed under a big heavy book - I use A4 tracing paper that I get in pad form from my local artist materials shop. I find that thoroughly dried and flattened plots are perfectly re-usable.With either HP Deskjet (670C or 895CXi), I can consistently obtain 0.005 inch exposed and developed resolution.Typesetters - for the best quality artwork, generate a Postscript or PDF file and take it to a DTP or typesetting service, and ask them to produce a positive film of it. This will usually have a resolution of at least 2400DPI, absolutely opaque black and perfect sharpness. The cost is usually 'per page' regardless of area used (UK£5 for A4 last time I did one), so if you can fit multiple copies of the PCB, or both sides onto one sheet, you'll save money. This is also a good way to do the occasional large PCB that won't fit your laser printer - sizes up to A3+ are widely available, and larger ones can also be done by more specialised services. Also a useful alternative for the highest-resolution boards that won't quite make it with other methods. Typeset artworks are good enough for production PCBs, but most PCB houses

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nowadays only accept gerber data, as it's easier for them to post-process for step & repeat etc.Laser printers - easily the best all-round solution. Very affordable, fast and good quality. The printer used must have at least 600dpi resolution for all but the simplest PCBs, as you will usually be working in multiples of 0.025" (40 tracks per inch). 300DPI does not divide into 40, 600DPI does, so you get consistent spacing and linewidth.It is very important that the printer produces a good solid black with no toner pinholes (pinholes in larger fill areas are acceptable). If you're planning to buy a printer for PCB use, do some test prints on tracing paper to check the quality first. If the printer has a density control, set it to 'blackest'. Even the best laser printers don't generally cover large areas (e.g. ground planes) well, but this isn't usually a problem as long as fine tracks are solid. Note that the blackness of the printing on paper doesn't always mean a good opaque result on tracing paper so always check with tracing paper if you're buying a printer for PCB work.

10.2 Photoresist PCB Laminate

Always use good quality pre-coated positive photoresist fibreglass (FR4) board. Check carefully for scratches in the protective covering, and on the surface after peeling off the covering. You don't need darkroom or subdued lighting when handling boards, as long as you avoid direct sunlight, minimuse unnecessary light exposure, and develop immediately after UV exposure.

10.3 Exposure

The photoresist board needs to be exposed to ultra-violet light through the artwork, using a UV exposure box.UV exposure units can easily be made using standard fluorescent lamp ballasts and UV tubes. For small PCBs, two or four 8 watt 12" tubes will be adequate, for larger (A3) units, four 15" 15 watt tubes are ideal. To determine the tube to glass spacing, place a sheet of tracing paper on the glass and adjust the distance to get the most even light level over the surface of the paper. Even illumination is a lot easier to obtain with 4-tube units. The UV tubes you need are those sold either as replacements for UV exposure units or insect killers. I've heard reports that 'black light' tubes for disco lighting etc. don't work very well (these have a black or dark purple appearance when off). The tubes you want look white when off (just like normal white lamps), and light up with a light purple, which makes flourescent paper etc. glow brightly. DO NOT use short-wave UV lamps like EPROM eraser tubes or germicidal lamps, which have clear glass - these emit short-wave UV which can cause eye and skin damage, and are not suitable for PCB exposure. Mega in the UK do cheap UV bulbs as replacements for their UV boxes. RS also stock a wide range of UV tubes, including U shaped ones

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- search for 'insect killer' on their site. Electrical suppliers like TLC also sell UV insect-killer tubes. A timer which switches off the UV lamps automatically is essential, and should allow exposure times from 2 to 10 minutes in 30 second increments. It is very useful if the timer has an audible indication (e.g. goes 'ping') when the timing period has completed. A mechanical or electronic timer from a scrap microwave oven would be ideal.Dead scanners make ideal cases for homemade UV boxes, but make sure the case is deep enough - a nice old clunky one, not a modern slimline thing ( unless you don't mind using a lot of tubes to get even illumination). Although it is probably possible to make a UV box with UV LEDs, you'd need so many to get a decent exposure area that it is almost certainly not worth even thinking about unless you happen to have a few hundred of them and nothing more interesting to use them for.Short-term eye exposure to the correct type of UV lamp is not harmful, but can cause discomfort, especially with bigger units. Use glass sheet rather than plastic for the top of the UV unit, as it will flex less and be less prone to scratches. Normal window glass works fine.You will need to experiment to find the required exposure time for a particular UV unit and laminate type - expose a test piece in 30 second increments from 2 to 8 minutes, develop and use the time which gave the best image. Generally speaking, overexposure is better than underexposure. (it's easier to add the odd wire-bridge than hack off a load of unwanted copper with a Dremel or deal with lots of hairline shorts on fine-pitch tracking)For a single-sided PCB, place the artwork, toner side up, on the UV box glass, peel off the protective film from the laminate, and place it sensitive side down on top of the artwork. The laminate must be pressed firmly down to ensure good contact all over the artwork, and this can be done either by placing weights on the back of the laminate (I use a few dead gel-cell lead-acid batteries for this), or by fitting the UV box with a hinged lid lined with foam rubber, which can be used to clamp the PCB and artwork. If you are using an old Scanner as a case, the lid will of course already be there.After exposure, you can usually see a feint image of the pattern in the photosensitive layer.

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10.4 Developing

The main thing to say here is DO NOT USE SODIUM HYDROXIDE for developing photoresist laminates. Use of Sodium hydroxide is the primary reason people complain about poor results when trying to photo-etch PCBs.It is completely and utterly dreadful stuff for developing PCBs - apart from it's causticity, it's very sensitive to both temperature and concentration, and made-up solution doesn't last long. Too weak and it doesn't develop at all, too strong and it strips all the resist off. It's almost impossible to get reliable and consistent results, especially so if making PCBs in an environment with large temperature variations (garage, shed etc), as is often the case for such messy activities as PCB making.

A much much better developer is a silicate based product, which comes as a liquid concentrate. I'm told this is sodium metasilicate pentahydrate Na2SiO3*5H2O (RS-Components data sheet item 690-849 and Safety data sheet). See sources below for method for making this developer.This stuff has huge advantages over sodium hydroxide, most importantly is is very hard to over-develop. You can leave the board in for several times the normal developing time without noticeable degredation. This also means it's not temperature critical - no risk of stripping at warmer temperatures. Made-up solution also has a very long shelf-life, and lasts basically until it's worn out (and even then you can just top up with more concentrate) - the concentrate lasts essentially forever.The lack of over-developing problems allows you to make the solution up really strong for very fast developing The recommended mix is 1 part developer to 9 parts water, but I usally make it stronger to develop MicroTrak laminate in about 5-10 seconds (yes, seconds - dip, rinse and it's done!) without the risk of over-development damage.You can check for correct development by dipping the board in the ferric chloride very briefly (or dribbling a few drops onto the surface) - the exposed copper should turn dull pink almost instantly, leaving the track pattern sharply defined. If any shiny copper coloured areas remain, or the gaps between tracks are 'blurry', rinse and develop for a few more seconds. If the board was under-exposed, you tend to get a thin layer of resist which isn't removed by the developer. You can often remove this by gently wiping with dry paper towel (Kitchen roll, preferably non coloured/patterned!) - the dry paper towel is just abrasive enough to remove the film without damaging the resist.You can either use a photographic developing tray or a vertical tank for developing - a tray makes it easier to see the progress of the development. You don't need a heated tray or tank unless the solution is really cold (<15°C). A defrost tray from a small scrap refrigerator is a possible alternatibe ( I have been known to use the tray from my fridge to develop & etch a particularly large PCB....).

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10.5 Etching

I've always used ferric chloride etchant - it's messy stuff, but easier to get and cheaper than most alternatives I've seen. It attacks ANY metal including stainless steel, so when setting up a PCB etching area, use a plastic or ceramic sink, with plastic fittings & screws wherever possible, and seal any metal screw heads etc. with silicone-rubber sealant. If copper water pipes may get splashed or dripped-on, sleeve or cover them in plastic (heat-shrink sleeving is great if you're installing new pipes). Fume extraction is not normally required, although a cover over the tank or tray when not in use is a good idea. If there is an easy way to vent fumes outside ( e.g. a cover over the tanks) this can make the fumes less objectionable but it's really not worth the hassle of setting up a powered extractor unless you have a particularly sensitive nose/throat. Power extraction is also rather problematic to do due to corrosion issues. You should always use the hexahydrate type of ferric chloride, which is light yellow, and comes as powder or big globular granules, which should be dissolved in warm water until no more will dissolve, giving a typically muddy brown solution. Adding a teaspoon of table salt helps to make the etchant clearer (looks like very very strong tea) for easier inspection. Anhydrous ferric chloride is sometimes encountered, which is a dark green-brown crystalline powder. Avoid this stuff if at all possible Use extreme caution, as it creates a lot of heat when dissolved - always add the powder very slowly to water, do not add water to the powder, and use gloves and safety glasses You may well find that solution made from anhydrous FeCl doesn't etch at all, if so, you need to add a small amount of hydrochloric acid and leave it for a day or two. Don't add too much acid though as it will produce very corrosive and choking fumes when warmed for etching. Sorry, I don't know what constitutes ' too much' as it's many years since I used anhydrous ferric chloride. Always take extreme care to avoid splashing when dissolving either type of FeCl - it tends to clump together in the container due to absorbing moisture, and you often get big chunks coming out of the container & splashing into the solution. It will damage eyes and permanently stain clothing and pretty much anything else - use gloves and safety glasses and wash off any skin splashes immediately. If you're making PCBs in a professional environment, where time is money, you really should get a heated bubble-etch tank. With fresh hot ferric chloride, a PCB will etch in well under 5 minutes, compared to up to an hour without heat or agitation. Fast etching also produces better edge quality and consistent line widths.

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10.6 Tin Plating

Although you can get special stripping solutions and hand applicators, most resists can be dissolved off more easily and cleanly using methanol (methylated spirit). Hold the (rinsed and dried) PCB horizontal, and dribble few drops of methanol on the surface, tilting the PCB to allow it to run over the whole surface. Wait about 10 seconds, and wipe off with a paper towel dipped in methanol. Repeat if any resist remains. I've left the old section on plating below, but I don't really think it's worth it except maybe in situations where you need a finish that lasts longer than the life of a typical prototype, e.g. for edge connectors or test-point pads, or for better cosmetic appearance. Tin-plating a PCB makes it a lot easier to solder, and is pretty much essential for surface mount boards. Unless you have access to a roller-tinning machine, chemical tinning is the only option. Unfortunately, tin-plating chemicals are expensive, but the results are usually worth it. If you don't tin-plate the board, either leave the photoresist coating on (most resists are intended to act as soldering fluxes), or spray the board with rework flux to prevent the copper oxidising. A 'flux pen' (available from Chemtronics & Multicore) be used to coat smaller PCBs. Made-up tinning solution deteriorates over time, especially in contact with air, so unless you regularly make a lot of PCBs, make up small quantities at a time (just enough to cover a PCB in the tinning tray) keep the solution in a sealed bottle (ideally one of those concertina-type bottles used for some photographic solutions to exclude air), and return it to the bottle immediately after use - a few days in an open tray and it can deteriorate badly. Also take care to avoid contamination, which can very easily render the solution useless. Thoroughly rinse and dry the PCB before tinning, keep a special tray and pair of tongs specifically for tinning (to avoid contamination), and rinse them after use. Do not top-up used solution if it stops tinning - discard it, clean & rinse the tray, and make up a fresh solution. Ensure the temperature of the tinning solution is at least 25ºC, but not more than 40ºC - if required, either put the bottle in a hot water bath, or put the tinning tray in a bigger tray filled with hot water to warm it up. Putting a PCB in cold tinning solution will usually prevent tinning, even if the temperature is subsequently raised. Preparation is important for a good tinned finish - strip the photoresist thoroughly - although you can get special stripping solutions and hand applicators, most resists can be dissolved off more easily and cleanly using methanol (methylated spirit). Hold the (rinsed and dried) PCB horizontal, and dribble few drops of methanol on the surface, tilting the PCB to allow it to run over the whole surface.

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Wait about 10 seconds, and wipe off with a paper towel dipped in methanol. Repeat if any resist remains. Rub the copper surface all over with wire wool (which gives a much better finish than abrasive paper or those rubber 'eraser blocks') until it is bright and shiny all over, wipe with a paper towel to remove the wire wool fragments, and immediately immerse the board in the tinning solution. Take care not to touch the copper surface after cleaning, as fingermarks will impair plating. The copper should turn a silver colour within about 30 seconds, and you should leave the board for about 5 minutes, agitating occasionally (do not use bubble agitation). For double-sided PCBs, prop the PCB at an angle to ensure the solution can get to both sides. Rinse the board thoroughly, and rub dry with paper towel to remove any tinning crystal deposits, which can spoil the finish. If the board isn't going to be soldered for a day or two, coat it with flux, either with a rework flux spray or a flux pen.

10.7 Drilling

If you're using fibreglass (FR4) board, which you almost certainly will be, you MUST use tungsten carbide drill bits - fibreglass eats normal high-speed steel (HSS) bits very rapidly, although HSS drills are OK for odd larger sizes (>2mm) that you only use occasionally where the expense of a carbide isn't justified. Carbide drill bits are expensive, and the thin ones snap very easily. When using carbide drill bits below 1mm, you MUST use a good vertical drill stand - you WILL break drill bits very quickly without one, and at UK£2-3 a pop, a drill stand will quickly pay for itself. Carbide drill bits are available as straight-shank (i.e. the whole bit is the diameter of the hole), or thick shank (also called 'turbo' or 'reduced' shank) , where a standard size (typically about 3.5mm or 1/8") shank tapers down to the hole size. I much prefer the straight-shank type for sizes below about 1mm because they break less easily, the longer thin section providing more flexibility. Straight-shank drills are also usually cheaper, but sometimes less easy to obtain. When drilling with carbide bits, it's important to hold the pcb down firmly, as the drill bit can snatch the board upwards as it breaks through, and this will usually break the drill bit if the board isn't held down. Small drills for PCB use usually come with either a set of collets of various sizes or a 3-jaw chuck - sometimes the 3-jaw chuck is an optional extra, and is worth getting for the time it saves changing collets. For accuracy, however, 3-jaw chucks aren't brilliant, and small drill sizes below 1mm quickly form grooves in the jaws, preventing good grip. Below 1mm you should use collets, and buy a few extra of the smallest ones, keeping one collet per drill size, as using a larger drill in a collet will

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open it out so it no longer grips smaller drills well. Some cheap drills come with plastic collets - throw them away and get metal ones.

You need a good strong light on the board when drilling to ensure accuracy. I use a 12V dichroic halogen lamp (under-run at 9V to reduce brightness) mounted on a microphone gooseneck for easy positioning (shown right). It can be useful to raise the working surface about 6" above normal desk height for more comfortable viewing. Dust extraction is nice, but not essential - an occasional blow does the trick! Note that fibreglass dust & drill swarf is very abrasive and also irritating to the skin. A foot-pedal control to switch the drill off and on is a very useful addiiton, especially when frequently changing bits. Typical hole sizes : ICs, resistors etc. 0.8mm. Larger diodes (1N4001 etc.), square-pin headers, D connectors, IDC connectors, TO-220 leads etc. : 1.0mm, terminal blocks, trimmers etc. 1.2 to 1.5mm. Avoid hole sizes less than 0.8mm unless you really need them. Always keep at least two spare 0.8mm drill bits, as they always break just when you need a PCB really urgently. 1.0mm and larger are more resilient, but one spare is always a good idea. When making two identical boards, it is possible to drill them both together to save time. To do this, carefully drill an 0.8mm hole in the pad nearest each corner of each of the two boards, taking care to get the centre as accurate as possible. For larger boards, drill a hole near the centre of each side as well. Lay the boards on top of each other, and insert an 0.8mm track pin (pictured below, under 'Through Plating') in 2 opposite corners, using the pins as pegs to line the PCBs up. Squeeze (with pliers or a vice ) or hammer the pins into the boards, and then insert and squeeze pins into the remaining holes. The two PCBs will now have been 'nailed' together accurately, and

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can be drilled together. Standard track pins are just the right length to fix standard 1.6mm PCBs together without potruding below the bottom board. On PCBs with several hole sizes, I'd suggest drilling the larger sizes first, as this reduces the chance of accidentally under-drilling a hole - something you typically only notice when the PCB is half-assembled, making it awkward to re-drill.

10.8 Cutting

If you do any serious amount of PCB work, a small guillotine (cost about £150) is very useful, as it's by far the easiest way to cut fibreglass laminate Mega Electronics (see sources) do a very nice one. Ordinary saws (bandsaws, jigsaws, hacksaws) will be blunted quickly unless they are carbide tipped, and the dust can cause skin irritation. Although tempting if avaliable, I would particularly advise against using a bandsaw as it will not only wreck the expensive blade quickly, the inevitable fibreglass dust is likely to do long-term damage to bearings etc. If using a hacksaw, use a long-frame type i.e. not junior) with adjsutable tension, and a medium or fine metal-cutting blade, with plenty of tension ( as tight as you can without snapping the blade). Clamp the PCB firmly, using a strip of wood to clamp the entire length of the board, close to the cut, with thin cardboard on each side of the board to avoid scratching the photoresist. Keep the saw blade angle as shallow as possible - this keeps the cut nice and straight. A carbide tile-saw blade in a jigsaw might be worth a try, but bear in mind it's easy to accidentally scratch through the protective film when sawing, causing photoresist scratches and broken tracks on the finished board - if using a jigsaw I'd suggest adding a layer of parcel tape to increase protection . If you have access to a sheet-metal guillotine, this is also excellent for cutting boards, providing the blade is fairly sharp.

To make cut-outs, drill a series of small holes, punch out the blank and file to size. Alternatively use a fretsaw or small hacksaw, but be prepared to replace blades often. With practice it's possible to do corner cutouts with a guillotine but you have to be very careful not to over-cut! A cheap nibbling tool like This one (pictured right) is very useful for making cutouts and shaping the board edge.

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If you use a saw to cut the board, take care to ensure the edges are square, as burrs on the board will raise it enough from the artwork for the UV light to get between the artwork and the board Check for burrs again once you have removed the backing sheet just before exposure.

10.9 Through – Plating

When laying out double-sided boards, give some thought to how top connections will be made. Some components (e.g. resistors, unsocketed ICs) are much easier to top-solder than others (e.g. radial capacitors), so where there is a choice, make the top connection to the 'easier' component. For s ocketed ICs, use turned-pin sockets, preferably the type with a thick pin section under the socket body. Lift the socket slightly off the board, and solder a couple of pins on the solder side to tack it in place, and adjust so the socket is straight.. Solder all the solder side pins, then solder the required top-side pins by reheating the joint on the solder side, while applying solder to the pin and track on the component side, waiting until the solder has flowed all round the pin before removing the heat (pictured right). On dense boards, think carefully about the best order in which to insert sockets to make access to top-side pins easier. When you have finished assembling the PCB, double-check that you have top-soldered all the required top pads, as unsoldered top-side pins can cause intermittent contact and be very hard to track down. Then when you can't get the board working, check again for top-side pins you forgot to solder - there's always at least one..! For vias (holes which link the two sides, without component pins in them), use 0.8mm snap-off linking pins (shown right), available from manyelectronics suppliers. (See Sources) These are much quicker than using pieces of wire. Just insert the bottom of the stick into the hole, bend over to snap off the bottom pin, repeat for other holes, then solder both sides. If you need 'proper' through-plated holes, for example to connect to inaccessible top-side pins, or for underneath surface mount devices (linking pins stick out too much for use here), Multicore's "Copperset" system works well, but the kit is very expensive (£190). It uses 'bail bars' (pictured right), which consist of a rod of solder, with a copper/tin sleeve plated on the outside. The sleeve is scored at 1.6mm intervals, corresponding to the PCB thickness. The bar

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is inserted into the hole using a special applicator, and bent over to snap off the single bail in the hole. It is then punched with a modified automatic centre-punch, which causes the solder to splay over the ends of the plated sleeve, and also pushes the sleeve against the side of the hole. The pads are soldered each side to join the sleeve to the pads, and then the solder is removed with braid or a solder sucker to leave a clear plated hole. Fortunately, it is possible to use this system for plating standard 0.8mm holes without buying the full kit. You can buy the bail bars seperately as refills (£24 for 500). For the applicator, use a 0.9mm automatic pencil, (the type which has a tip like the one pictured right, e.g. Berol PCL2000), which actually works much better than the original applicator, as you get one bail for every press of the button, and it has a metal nose instead of the original plastic one. Get a small automatic centre-punch, and grind the tip off so it's completely flat - this works fine for punching the bails. For an anvil, use a thick flat piece of metal - the back of a large heatsink is perfect for this - plate all the holes before fitting any components so the bottom surface is completely flat. Holes must be drilled with a sharp 0.85mm carbide drill to get the hole size right for the plating process..

10.10 Through – Plating Using Rivets

This riveting system is another way to do through-plating on dense PCBs. The rivets can be used quite easily on their own without the punch tool, just a pair of fine tweezers (and a steady hand...).The 0.4mm rivets (pictured) fit a 0.6mm hole and so can be used on quite dense groups of 0.05" pad dia vias.

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11. References

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11. References

a. “Atmel AVR Microcontroller Primer” -By Steven F. Barrett & Daniel J. Pack b. “Microcontroller Fundamentals for Engineers and Scientists” – By S Barrett & D Pack

c. Atmel 8-bit AVR Microcontroller with 16K Bytes In – System Programmable Flash, Atmega16, data sheet : 2466L – AVR – 06/05, Atmel, San Jose, CA.

d. J Hennessy and D Patterson, “Computer Architecture : A Quantitative Approach” 3rd ed, Morgan Kaufman, San Francisco, CA, 2003