8/13/2019 Project Steps Mintduino Transfer to Circuit Board

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Project Steps View All 1. Build Preparation & Things to Consider 2. Power Regulation: 9V to 5V 3. Voltage regulator and Capacitor 4. Another Capacitor and Layout Planning 5. Red LED 6. 9V Battery Clip 7. Testing the Circuit 8. Integrated Circuit Socket 9. Integrated Circuit 10. Crystal & Capacitors 11. ATmega328P Power & Ground Take One 12. ATmega328P Power & Ground Take Two 13. LED for Blink Sketch (Optional) 14. Reset Button 15. FTDI 16. FTDI Wiring 17. FTDI and a Capacitor

Step #1: Build Preparation & Things to Consider

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Experience building the breadboard MintDuino is not necessary, but it might help youappreciate the board layout. This project mimics the build steps of the original

MintDuino kit. If you need more explanation of the circuit, check outthe original

MintDuino project.

Not all perfboards are electrically identical to breadboards. Electrically connectedholes on a board are often called strips. All sorts of names exist for different overall

board layout of strips, but you do not need to learn them. All you really need to do is

look at your perfboard and determine if it has any strips or not. If it has strips, such as

the board in this project, then look to determine how similar or dissimilar the

component layout will be given the strip orientation. Planning ahead is your best

tactic in doing a new layout!

Note:the perfboard in this build is not identical to a breadboard i.e. the connectedstrips exist, but they are electrically different in layout.

Step #2: Power Regulation: 9V to 5V

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The first sub-circuit to layout and solder handles voltage regulation and the powerLED indicator.

Gather the 7805 voltage regulator, two 10uF capacitors, a red LED, and wire.Step #3: Voltage regulator and Capacitor

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Place the voltage regulator at the very top of your perfboard and solder the threeleads. For the board to fit in the tin, you need to adjust the regulator to have the leads

slightly exposed enough to bend down parallel with the board.

Place one 10uF capacitor adjacent to the voltage regulator. This component ispolarized, which means the leads must be placed properly or the circuit will not

function. The white stripe on the barrel of the capacitor in the image indicates thenegative lead.

Step #4: Another Capacitor and Layout Planning

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Place the second 10uF capacitor (seen behind the voltage regulator). We will use thecenter two rails, the "power rail," which are connected lengthwise. You might not be

thinking yet about layout design, but it's important that you consider it.

Traditional component layout would place the IC centered on the board and surroundthe chip with support peripherals, such as the power regulation circuit we are building

now. Traditions are great to know, but spanning a 28-pin IC over the only two rails ofcontiguous lengthwise connection is problematic for adding in more components

later.

Not having the IC in the center of the perfboard is the first big component layoutdecision that effects the layout. Since all components in a layout influence each other,

28-pins is a lot of influence!

Note:Placing the IC off-center will also allow room for the 9V battery inside the tin,as mentioned in the introduction.

Step #5: Red LED

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The red LED illuminates when power is properly distributed through the circuit. Some LEDs will rest flush against the perfboard, but this tiny 5mm LED just does

not. Use masking tape to affix the part while you solder it into position.

The LED requires power and ground to function. Connect a red wire to the positiveterminal of the LED and the power rail. Take a 220 resistor and solderthat between

the negative terminal of the LED and the ground rail of the perfboard. Remember wedecided that power and ground are the two adjacent rails that run lengthwise when the

board is oriented in "portrait."

Step #6: 9V Battery Clip

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We don't want to connect the 9V battery clip directly to the power and ground rails ofthe circuit. Instead, we need to have the power regulated and "smoothed" by the

circuit. Masking tape is again helpful to position the wires while you solder.

The black wire of the battery clip connects to the negative rail of the capacitor(remember, negative connects to negative). Compare your layout with image two and

solder in place. The red wire of the battery clip connects to the positive rail of the capacitor. Before

you solder the wire double-check that the wires are not tangled.

Step #7: Testing the Circuit

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Plug a 9V battery into the clip. Once connected the red LED will illuminate. If the LED does not illuminate or flickers, quickly disconnect the battery and check

your soldering for bad joints.

Congratulations! You just built a 5V regulated power supply.Step #8: Integrated Circuit Socket

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Integrated Circuits (IC) such as the ATmega328P can be directly soldered to aperfboard, but if you fry the chip, there is not a simple fix. Thankfully IC sockets

exist! The socket is soldered to the perfboard and the IC snaps into the socket.

Though the MintDuino does not come with any IC sockets, they are cheap and wellworth tracking down. If you cannot find the right pin number at a local supplier, no

worries! You can actually combine multiple IC sockets by simply placing them inadjoining holes.

Make your life easier and temporarily secure the IC socket to the perfboard while yousolder it in place.

Step #9: Integrated Circuit

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Install the ATmega328P into the IC socket. Notice the perfboard has been rotated180 and a sticker from theMaker's Notebookapplied to the IC for helpful reference.Step #10: Crystal & Capacitors

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The crystal is non-polarized, so the orientation does not matter. What matters,however, is that the crystal connects to pin 9 and 10 of the ATmega.

Pin numbering can be tricky. Image two depicts the ATmega328P and two differentnumbers of the chip. The left illustration shows pin numbering according to the

manufacturing data sheet. On the right illustration the pin numbering corresponds to

the Arduino nomenclature. Add two 22pF capacitors. One leg of the capacitor connects to a crystal leg, the other

connects to ground. This is done twice; once for each leg of the crystal (image 3).

Step #11: ATmega328P Power & Ground Take One

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Cut a small black wire and use it to connect ATmega pin 8 and the ground rail. Cut a small red wire and use it to connect ATmega pin 7 and the power rail. If you forget which rail is power and which is ground look at the capacitor on the

power rail. On the capacitor housing should be a stripe which indicates the negative

side of the component.

Step #12: ATmega328P Power & Ground Take Two

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The ATmega requires three additional power-related connections: one for groundconnecting pin 22 to the ground rail (image 1) and two for power connecting pins 20

and 21 each to the power rail (images 2 & 3).

Rather than route long wires for power and ground over the ATmega, this layoutroutes the wires on the underside of the perfboard.

This underside wiring approach demonstrates one method to reduce wire-clutter onyour perfboard, but is not particularly easy to solder. On scrap perfboard attempt

soldering a couple of wires to improve your technique -- I should have done this too!

Step #13: LED for Blink Sketch (Optional)

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220 resistor: connect one lead to the ground rail and the other to the negative lead ofthe green LED. Cut a long wire to connect one end to pin 19 on the ATmega and the other to the

positive lead on the LED.

Remember pin 19 is the datasheet number; using Arduino nomenclature you areconnecting this wire to digital pin 13. If this is confusing, consult step 10.

This step is completely optional and the components are not necessary for theMintDuino to function. Rather, these components physically express the blink sketch

that is pre-loaded on the kit's ATmega.

Step #14: Reset Button

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Solder the reset button so it spans the perfboard in the same manner as the IC-socket.Do this -- and all soldering -- while the power is not connected.

Wire one of the button terminals to ground with a black wire (image 2, rotated). Nestled under the reset button's black wire is a 10k resistor (brown, black, orange)

connecting pin 1 and the power rail.

Step #15: FTDI

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Unlike Rev. 3 Arduino UNO boards, the MintDuino does not have an FTDI chiponboard. Instead, the MintDuino breaks out a connection where you attach anFTDIFriend.

Connect the breakout pins (a strip of six header pins) and then brace yourself for moreunder-board soldering!

Solder the six breakout pins.Step #16: FTDI Wiring

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Notice the upper-right corner of the board in the first image. The black wire connectsthe sixth pin of the FTDI breakout to the ground rail. The board in these images is

oriented so that both the ATmega and the FTDI cable number from left to right.

Cut a long black wire and connect this from pin 1 of the ATmega to a hole adjacent tothe FTDI breakout pins (image 2).

Cut two more black wires. One wire connects pin 2 on the ATmega to pin 3 of theFTDI header pins (image 3).

The second black wire you cut connects pin 3 on the ATmega to pin 2 of the FTDI(also image 3).

Step #17: FTDI and a Capacitor

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Remember the long black wire attached from pin 1 of the ATmega to the holeadjacent to the FTDI breakout? Place the 100nF capacitor so it connects this black

wire to pin 1 of the FTDI. The first image shows the long legs of the capacitor from

the underside of the perfboard.

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