ESQUEMAS DE CIRCUITOS ELECTRÓNICOS

7/29/2019 ESQUEMAS DE CIRCUITOS ELECTRNICOS

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ESQUEMAS DECIRCUITOSELECTRNICOS

DIEGO GUEVARA


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1.5V LED Flashers

The LED flasher circuits below operate on a single 1.5 volt battery. The circuiton the upper right uses the popular LM3909 LED flasher IC and requires only atiming capacitor and LED.

The top left circuit, designed by Andre De-Guerin illustrates using a 100uFcapacitor to double the battery voltage to obtain 3 volts for the LED. Twosections of a 74HC04 hex inverter are used as a squarewave oscillator thatestablishes the flash rate while a third section is used as a buffer that chargesthe capacitor in series with a 470 ohm resistor while the buffer output is at+1.5 volts. When the buffer output switches to ground (zero volts) thecharged capacitor is placed in series with the LED and the battery which

supplies enough voltage to illuminate the LED. The LED current isapproximately 3 mA, so a high brightness LED is recommended.

In the other two circuits, the same voltage doubling principle is used with theaddition of a transistor to allow the capacitor to discharge faster and supply agreater current (about 40 mA peak). A larger capacitor (1000uF) in series witha 33 ohm resistor would increase the flash duration to about 50mS. Thediscrete 3 transistor circuit at the lower right would need a resistor (about 5K)in series with the 1uF capacitor to widen the pulse width.


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A / D Conveter - 8Bit With Output Current-To-Vol tage Conversion


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HF Broadband Antenna PreAmp

The HF/SW receiver preamplifier is comprised of broadband toroidaltransformer (L1-a and L1-b), LC network (comprised at 1600-kHz, high-passfilter and 32-MHz, low-pass filter), L2 and L3 (26 turns of #26 enameled wirewound on an Amidon Associates T-50-2, red, toroidal core), a pair of resistiveattenuators (ATTN1 and ATTN2), and a MAR-x device.

Shown here is the composition of basic 1-dB pi-network resistor antenuator.This is the method of supplying dc power to a preamplifier using only the RFcoax cable.


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Amateur Radio Linear Amplifier 2-30MHz 140W

The amplifier operates across the 2-30 MHz band with relatively flat gainresponse and reaches gain saturation at approximately 210 W of outputpower. Both input and output transformers are 4:1 turns ratio (16:1impedance ratio) to achieve low input SWR across the specified band and ahigh saturation capability. When using this design, it is important tointerconnect the ground plane on the bottom of the board to the top,especially at the emitters of the MRF454s.


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80-M Amateur Radio Transmitter

This transmitter consists of a keyed crystal oscillator/driver and a highefficiency final, each with a TMOS Power FET as the active element. The totalparts cost less than $20, and no special construction skills or circuit boardsare required.

The Pierce oscillator is unique because the high Crss of the final amplifierpower FET, 700-1200 pF, is used as part of the capacitive feedback network.In fact, the oscillator will not work without Q2 installed. The MPF910 is a goodchoice for this circuit because the transistor is capable of driving the finalamplifier in a switching mode, while still retaining enough gain for oscillation.To minimize cost, a readily-available color burst TV crystal is used as thefrequency-determining element for Q1.

An unusual 84% output efficiency is possible with this transmitter. Such highefficiency is achieved because of the TMOS power FET's characteristics alongwith modification of the usual algorithm for determining output matching.


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Low-Power 40-Meter CW Transmiter

This CW transmitter has an output of up to 3 W. By using 24 V on Q2, up to 10W output can be obtained, If a 24-V supply is used, Q1 must not see morethan 12V. Connect 12V between junctions C3, R2 and L2, and remove L5. L1

should be a low-Q 18- to 20-uH inductor. R6 can be used (up to 47 ohm) toreduce the Q further.

Amplifier - 8 Watts


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Amplifier - 22 Watts

IC [U1] TDA1554

The circuit dissipates roughly 28 watts of heat, so a good heatsink isnecessary. The chip should run cool enough to touch with the properheatsink installed.

The circuit operates at 12 Volts at about 5 Amps at full volume. Lowervolumes use less current, and therefore produce less heat. R1 is also a5% resistor.


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Amplifier - 29MHz


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The Audio / Video Distribution Amplifier

With the amount of equipment in home entertainment centers today the needto be able to vary the gain of the audio or video signal is needed. I found thisparticular circuit helpfull when used in conjuction with the UniversalDescrambler and a Stabilizer circuit I built for making copies of video tapes. Itnot only allowed me the ability to fine tune the video strength it also helpedme increass the recorded audio which typically becomes poor when makeing

tape copies

Circuit operation is straight forward for amplifier circuits. The second channelfor the audio amplifer is made up of the same componets except the otherhalf of IC1 is used. Pin 6 & 5 are inputs and 7 is the output


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Differential Amplifier

This circuits will take it's two inputs and amplify their difference


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Differential Amplifier - True Balanced Input

This circuits will take it's two inputs and amplify their difference...with a

balanced input...


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Amplifier - Inverting / Non Inverting

The non-inverting amplifier will give you 15db gain, and the inverting

amplifier will take the signal that's coming in and give the opposite on theoutput.

Power Amplifier - 10W

This amplifier will make a great addition to your tape / cd player.


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Amplifier / Compressor - Low Distortion

Designers can build a 15-dB compressor with a miniature lamp and a current-feedback amplifier. The circuit possesses extremely low distortion atfrequencies above lamp's thermal time constant. This means that distortion isnegligible from audio frequencies to beyond 10 MHz. There's also relativelylittle change in phase versus gain compared to other automatic gain-controlcircuits. Lastly, the circuit has many instrumentation, audio, and high-frequency applications as a result of its low distortion and small phasechange.

The AD844 op amp is a perfect fit for this application because it's a current-feedback amplifier. Each stage of the circuit, U2, lamp, and feedback resistorcompresses an ac signal by over 15dB (see the figure). Cascading a number ofstages delivers higher compression ranges.

Op amp U1 operates as a unity-gain buffer to drive the input to thecompressor. However, U1 is optional if a low-impedance signal source is used.The lamp's resistance will increase with temperature, which reduces theration of resistor R3 to the resistance of the lamp. This ratio reduces the gainof U2. The lamp's cold resistance should be greater then the input resistance

of U2 (more then 50 ohms) for proper operation. The lamp's resistance willchange slightly for low input levels. Therefore, the ratio of R3 to theresistance of the lamp and the gain of U2 stays high.


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Power Amplifier - 12W, Low-Distortion

Power Amplifier - 20 Watts

This circuit will add 20 Watts of power to your audio signal.


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Audio Frequency Meter

The meter uses time averaging to produce a direct current that is proportionalto the frequency of the input signal.

Audio LED VU Meter

This circuit will desplay audio input in LEDs, each LED is a frequencylevel....just like the things on your stereo.


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Audio LED VU Meter - 2

IC [U1] LM3915

Audio Pre-Amplifier

This circuit will is useful if you have a microphone or a device that produces alow audio level and you want to connect it to a stereo or something. Thiscircuit will boost it's output level.


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Remote Loudspeaker

Audio Pre-Amplifier - Single IC

This circuit will is useful if you have a microphone or a device that produces alow audio level and you want to connect it to a stereo or something. Thiscircuit will boost it's output level.


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Car Voltage Gauge

The Car Voltage Gauge is based on 3 parts. The input circuit is an Analog toDigital Converter (IC2 CA3162E). The purpose of this chip is to sample ananalog voltage and convert it to a decimal value which is read by a

Display/Decoder Driver (IC1 CA3161E). This chip will turn each seven segmentdisplay on through the driver transistor Q1 - Q3. The power is derived fromthe car and is converted to 5 voltsby the 5 volt regulator. The circuit works as follows: The 10uf capacitor ischarged up by the cars voltage. Its value is then read by IC2 and a decimalvalue of that voltage is provided to IC1 which multiplexes the three displayunits. Each display is turned on sequentially with its appropriate valuedisplayed.The transistors Q1 through Q3 control the drive to each seven segmentdisplay. By monitoring the cars voltage with an accurate multimeter you canadjust the "Zero Adj." pot and the "Gain Adj." pot for accurate readings. LED 1

and 2 are optional. They can be used to indicate power on or can light up acut out display that says "Volts". This can be made by a plastic module thathas a thin plastic cover on it with the word "Volts" cut into it. The LED's wouldbe mounted inside the module.


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CMOS Circuits With RC Timing


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Combination Lock

When button S12 (#) is pressed, a positive voltage fed through Rl appears atthe base of transistor Ql, turning it on. When Ql is conducting, pin 1 of Ul isbrought to ground (low) or the battery's negative terminal. With pin 1 low,

two things occur: Pin 8 of Ul goes high (+ 9 volts dc), turning on LED 1-indicating that the circuit has been armed-and pin 13 goes from high to low.Transistor Q2 requires a low signal or negative voltage on its base in order toconduct. It also needs a positive voltage on its emitter and a negative voltageon the collector. As long as the door switch (Sl5) remains open (with the dooritself closed), Q2's emitter will not receive the necessary positive voltage. If,however, an unauthorized person opens the door, thus closing switch S15 andplacing a positive voltage on the emitter of Ql, the following sequence occurs:

1) Transistor Q2 conducts, receiving the necessary biasing current through acurrent-divider network consisting of resistors R3 and R4.

2) As Q2 conducts, a voltage drop is developed across the voltage dividersmade up of resistors R5 and R6. With R5 at 10,000 ohms and R6 at 1000 ohms,approximately one volt appears at the gate of SCR1. That's enough voltage totrigger the SCR's gate.


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DC Motor Speed Control

With this circuit you can make a DC motor go faster and slower...


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Digital Entry Lock

A block pinout diagram of the LS7220 keyless-lock IC is shown. The keypadmust provide each key with a contact to a common connection. In this case,the common connection goes to the positive supply rail so that when a key is

pressed, a positive voltage is passed through to the wire associated with thatkey. Each of the 12 keys are brought out to separate wires, and each wire isconnected to a different pin of a 24-pin socket (SO1).

To activate (unlock) the circuit, a preprogrammed four-digit access code mustbe entered in the proper sequence. The four-digit access code must beentered in the proper sequence. The four-digit access is programmed into thecircuit by connecting jumpers between terminals of a 24-pin plug-in header.

When the correct access code is entered (in the proper sequence), positivevoltages appear at pins 3, 4, 5, and 6 of Ul. That causes Ul to output apositive voltage at pin 13, which is fed through resistor R2 to the base of Ql,causing it to conduct. With Ql conducting, its collector is pulled to groundpotential, energizing relay Kl. The normally open relay contacts close,switching on any external device.

Capacitor C2 controls the total time that the output of Ul at pin 13 is positiveafter the release of the first key. With a value of 3.3 uF for C2, active timeafter release of the first key is about two seconds, assuming a 6-V supply orfour seconds with a 12-V supply. Therefore, if you push the subsequent keystoo slowly, the relay might not close at all! To increase the time allotted for

code entry, you will have to increase the capacitance of C2


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Digital Volume Control

Capacitor [C1] 0.1uF

IC [U1] DS1669

S1 turns the volume up, S2 turns it down. The input signal should not fall below -0.2 volts.

This digital volume control has no pot to wear out and introduces almost nonoise in the circuit. Instead, the volume is controlled by pressing UP andDOWN buttons. This simple circuit would be a great touch to any home audioproject.

Discrete OP Amplifier


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Digital Weight Scale

This circuit employs a potentiometer as the weight sensing element. Anobject placed upon the scale displaces the potentiometer wiper, an amountproportional to its weight. Conversion of the wiper voltage to digitalinformation is performed, decoded, and interfaced to the numeric display.


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Fiberoptic Interface

An op amp is used to interface between a fiberoptic system and the MOS SCRto multi-cycle, half-wave control of a load. This receiver has twocomplementary outputs, one at a quiescent level of about 0.6V and thesecond at 3V. By adding a 4.7V zener in series with the return bus, theeffective Vcc becomes 5.3V and also the 0.6V output level is translated up toabout 5.3V. This level is compatible with the reference input (5.9V) of the

single-ended powered op-amp acting as a comparator.


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Fiberoptic Receiver - 10MHz

The receiver will accurately condition a wide range of light inputs at up to 10Mhz data rates. The optical signal is detected by the PIN photodiode andamplified by a broadband fed-back stage, Q1-Q3. A second, similar, stage

gives further amplification. The output of this stage (Q5's collector) biases a2-way peak detector (Q6-Q7). The maximum peak is stored in Q6's emittercapacitor while the minimum excursion is retained in Q7's emitter capacitor.The dc value of Q5's output signal's mid-point appears at the junction of the0.005uF capacitor and the 22M ohm unit. This point will always sit midwaybetween the signal excursions, regardless of absolute amplitude. This signal-adaptive voltage is buffered by the low bias LT1012 to set the trigger voltageat the LT1016's positive input. The LT1016's negative input is biased directlyfrom Q5's collector.


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Infrared Remote Control

Transmisor

Receptor

omponent: Value: omponent: Value:

Resistor [R1] 11K, W Capacitor [C7] 1.5uF, 16V

Resistor [R2] 1M, W Transistor [Q1] 2N2222

Resistor [R3] 1K, W Transistor [Q2] 2N2907

Resistor [R4, R5] 100K, W Transistor [Q3] NPN Phototransistor

Potentiometer [R6] 50K Diode [D1] 1N914

Capacitor [C1, C2] 0.01uF, 16V IC [IC1] LM308

Capacitor [C3] 100pF, 16V IC [IC2] 567

Capacitor [C4] 0.047uF, 16V LED [LED1] Infrared LED

Capacitor [C5] 0.1uF, 16V Relay 6V Relay

Capacitor [C6] 3.3uF, 16V Switch [S1] SPST Push Button

Battery [B1] 3V

To adjust the circuit, hold down S1 while pointing LED1 at the receiver.Adjust R6 until you hear the relay click.

You can increase range by using a high output LED for LED1.

Bright light will stop the receiver from responding to the transmitter.A simple one-channel remote control. It will trigger a relay upon press of abutton.


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Low-Battery Detector

Comparator A detects when the supply voltage drops to 4 V and enablescomparator B to drive a piezoelectric alarm.

Is: 6V at 45 mA.

Is: 3.8 V at 1 mA.

f: 3 kHz.


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Low Voltage Battery Disconnect

This circuit will disconnect the battery when voltage falls below a certainlevel which you set


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DC Millivoltmeter

An LF356 op amp is used as a gain amplifier with the output taken across R5.When a full-scale current of 1 mA is flowing through the meter, exactly 1 Vappears across R5 (should be 1% tolerance or better). This is fed back to R2 tothe summing junction of IC1 (a full-scale produces 1uA). This offsets thecurrent through R1. R1 has a value of 1 M ohm/V which is used to zero themeter. R4 provides some overcurrent protection for the meter.

Optical Toggle Switch


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Moisture Detector

A bar-graph LED driver is used to drive 10 LEDs to give a relative indication ofmoisture. The moisture probes are connected so that electrical conductivitydue to moisture tends to forward bias Q1, providing a dc voltage at pin 5 ofU1 that is proportional to leakage current. Ideally, the probes should be madeof stainless steel.


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Panning Circuit - Voltage Controlled


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PC Serial Port Receiver

Component: Value:

Resistor 1K

Resistor 150K

Resistor 75K

Resistor 23K

Capacitor 510pF

Capacitor 1800pF

IC 4013

IC 4011

IC 74HCT164

IC 4017

Transistor 2N3053

This circuit was designed to control a 32 channel Christmas light show fromthe PC serial port. Originally designed with TTL logic, it has been simplifiedusing CMOS circuits to reduce component count. It is a fairly simple, reliablecircuit that requires only 4 common CMOS chips (for 8 outputs), an opticalisolator, and a few discrete components. The schematic diagram (SERIAL.GIF)illustrates the circuit with 16 outputs which can be expanded withadditional 8 bit shift registers.


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DisclaimerThis circuit requires physical connections be made to the computer's serial

port (COM1 or 2). To the best of my knowledge, it is difficult to causedamage to yourself or your computerby improper connections to this port, but there is no guarantee that damage

will not result. Use caution when making any external electrical connections.

Basic RS232 serial transmission

Serial data is transmitted from the PC as a series of positive and negativevoltages on a single wire which occur at predetermined times established bythe baud rate. Both the transmitter and receiver must be operating at thesame baud rate so that the receiver knows when to expect the next bit ofinformation. For the PC serial port, baud rate and bit rate are the same thing,but this is not necessarily true with modems that can detect more than twostates of the line.

In the quiescent state, with no load on the line, the voltage on the transmitline (pin 2 of the 25 pin connector) will be about -12 relative to the signalground (pin 7), which corresponds to a logical "1". The output impedance ofthe serial port is about 1K ohm which yields about 6 milliamps at 6 volts. Atypical data transmission frame consists of a start bit, 8 data bits, and one tothree stop bits. The start bit which is always positive, signals the beginning ofthe transmission and is used by the receiver to synchronize the clock so thatthe data bits can be sampled at the proper times. After the 9th time intervalpasses (start bit plus 8 data bits) a dead time occurs which allows the receiver

time to get ready for the next character. This dead time is referred to as astop bit, which is always negative or the same as the quiescent state. Thecircuit described here requires two stop bits of dead time for reliableoperation. More sophisticated circuitry would require only one.

Transmitted character examples

The letter "A" has a ASCII decimal value of 65. The "1" and "64" bits aretransmitted as a negative voltage (logical "1"), and the others are transmittedas a positive voltage (logical "0"). 64 + 1 = 65 = "A"

+ _____ _ _____________ ____________ ___ ___ __| | | | | || | | | | |

- - - - - - - - - - - - - - - - - - - - - - -- -

St ar t D0 D1 D2 D3 D4 D5 D6 D7 St opSt op

Deci mal val ue 1 2 4 8 16 32 64 128

Recei ver ' sCl ock _______ __ __ __ __ __ __ __

____________| | | | | | | | | | | | | | | |

| | | | | | | | | | | | | | | |- - - - - - - - - - - - - - - -


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The letter "B" has a ASCII decimal value of 66. The "2" and "64" bits aretransmitted as a negative voltage (logical "1"), and the others are transmittedas a positive voltage (logical "0"). 64 + 2 = 66 = "B"

+ ___________ ____________ ___________ _____| | | | | || | | | | |

- - - - - - - - - - - - - - - - - - - - - - -- -

St ar t D0 D1 D2 D3 D4 D5 D6 D7 St opSt op

Circuit operation

The input terminals (pins 1 and 2) of the optical isolator are connectedthrough a 1K resistor to the transmit and signal ground pins of the PC's serial

port (pins 2 and 7 of the 25 pin connector). A small signal diode is connectedacross the isolator input terminals to protect the isolator from reversevoltage. In the idle state, the isolator input voltage will be about -0.7 voltsand the isolator LED and transistor will be off. When a start bit is received,about 5 milliamps will flow through the isolator LED causing the isolatortransistor to conduct at about 80 microamps which in turn causes the externalswitching transistor (Q1) to turn off. The rising voltage at the collector of Q1is coupled through a 510 pF capacitor to produce a narrow positive pulsewhich sets the Q output of the first RS data latch (1/2 CD4013) and enablesthe dual NAND gate clock oscillator.

The clock oscillator runs at a frequency equal to the baud rate (9600 Hz) andmust maintain a frequency accuracy of less than 5% over the temperaturerange. High stability R and C components are recommended.

The clock output is delayed by one cycle so that the start bit will not bereceived as a valid data bit. This is accomplished by the two remaining NANDgates (1/2 CD4093) and the second RS data latch (1/2 CD4013). One of thesegates is used to invert the clock phase so that the first clock edge seen by thelatch (clock pin 11) will be going the wrong direction and so ignored. Theremaining gate, which is enabled by the second latch, opens on the third

clock edge, but also inverts the clock phase, and so supplies a falling clockedge to the counter and shift registers which is again the wrong direction, andis ignored. The fourth clock edge will be rising and active and will occur nearthe middle (about 52 microseconds) of the first data bit which will be shiftedinto the registers. The remaining 7 bits are shifted into the registers on eachsuccessive rising clock edge. Data is inverted at the register outputs, a logical"1" will correspond to zero volts, and a logical "0" will correspond to +6 volts.Transmitting character (255) will set all outputs low, and transmitting

character (0) will set them all high.

The 4017 decade counter increments one count on each rising clock edge and

resets both data latches on the 8th edge. This in turn stops the clock andresets the counter, and the circuit remains in a waiting state until the next


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start bit arrives. Two stop bits of dead time are required to allow the voltageat the input of the NAND gate (pin 2) to reach a logic "1" before the next startbit arrives. Erratic operation may occur when 2 or more characters aretransmitted as a string and only one stop bit is used.

The circuit may be modified to run at different baud rates by adjusting theclock frequency. This can be accomplished by temporally connecting pin 6 ofthe CD4013 to the positive supply and then selecting R and C values for thedesired frequency. You may need to use a 1% resistor or a couple 5% resistorsin series or parallel to get the value close enough. Or use a variable resistor inseries of about 10% the total value.

At 9600 baud, data output at the shift registers will be unstable for about amillisecond per word while the incoming data bits are shifted into theregisters and the existing bits are shifted out (into bit heaven). Higher baudrates will reduce this time proportionally and the original circuit operates at

57.6K baud to eliminate a slight flickering of the lights which was noticed at9600.

The 74HCT164 shift register outputs will sink or source about 4 milliamps at 6volts which can be increased with medium power transistors or FETs to driverelay coils, incandescent lights and other electronic devices. If relays areused, a small signal diode will need to be added across the relay coil tosuppress the inductive voltage.

Power supply

It is recommended that 0.1 uF capacitors be installed near the power pins ofeach CMOS device and a well regulated/filtered power supply be used. Fortest purposes, a 6 volt battery will work but the clock frequency will changeslightly with power supply voltage variations.

CD4011 Quad NAND gate

14 | Vdd________| _______| || CD4011 |

| | _ __ _ |1 - - - - - | - - - - | \ |

| | 0 - - - | - - - - - 32 - - - - - | - - - - | _ ___/ |

| | || || | _ __ _ |

5 - - - - - | - - - - | \ || | 0 - - - | - - - - - 4

6 - - - - - | - - - - | _ ___/ || | || || | _ __ _ |

8 - - - - - | - - - - | \ || | 0 - - - | - - - - - 109 - - - - - | - - - - | _ ___/ |


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| | || || | _ __ _ |

12 - - - - - | - - - - | \ || | 0 - - - | - - - - - 11

13 - - - - - | - - - - | ____/ |

| | || ________________||

7 | Vss

CD4013 Dual ' D' Type Fl i p- Fl op

14 | Vdd________| _______| |

6 - - - - - | Set 1 Q1 | - - - - - 15 - - - - - | D1 |3 - - - - - | Cl ock 1 _ |4 - - - - - | Reset 1 Q1 | - - - - - 2

| || CD4013 || |

8 - - - - - | Set 2 Q2 | - - - - - 139 - - - - - | D2 |

11 - - - - - | Cl ock 2 _ |10 - - - - - | Reset 2 Q2 | - - - - - 12

| ________________||

7 | Vss

CD4017 Decade Count er / Di vi der

16 | Vdd________| _______| || CD4017 || || " 0" | - - - - - 3| " 1" | - - - - - 2| " 2" | - - - - - 4

14 - - - - - | Cl ock "3" | - - - - - 7| " 4" | - - - - - 10

13 - - - - - | Cl ock "5" | - - - - - 1| Enabl e "6" | - - - - - 5| " 7" | - - - - - 6

15 - - - - - | Reset "8" | - - - - - 9| " 9" | - - - - - 11| Carr y out | - - - - - 12| ________________|

|8 | Vss

74HCT164 8 Bi t Ser i al - I n / Par al l el - Out Shi f t Regi st er

14 | Vdd________| _______| || 74HCT164 |

| |1 - - - - - | AND Gat ed Q0 | - - - - - 3


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| Ser i al Q1 | - - - - - 42 - - - - - | I nputs Q2 | - - - - - 5

| Q3 | - - - - - 6| Q4 | - - - - - 10

9 - - - - 0| Reset Q5 | - - - - - 11| Act i ve Q6 | - - - - - 12

| Low Q7 | - - - - - 13| |8 - - - - - | Cl ock |

| ________________||

7 | Vss

Ser i al port mal e D- SUB connect ors as seen f r omout si de t he PC.

1 13 1 5_____________________________ _____________( . . . . . . . . . . . . . ) ( . . . . . )\ . . . . . . . . . . . . / \ . . . . /

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -14 25 6 9

Name Output / I nput 25 pi n 9 pi n- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Tr ansmi t Dat a O 2 3Recei ve Data I 3 2Request To Send O 4 7Cl ear To Send I 5 8Dat a Ter mi nal Ready O 20 4Dat a Set Ready I 6 6Ri ng I ndi cat or I 22 9Dat a Car r i er Det ect I 8 1Si gnal gr ound - 7 5Power l i ne gr ound - 1 -

QBasic test program for 8 bit receiver

CLSDEFINT A-ZPRINT "Test sequence in progress, press any key to quit."OPEN "COM1:9600,n,8,2,CD0,CS0,DS0,OP0,RS,TB2048" FOR OUTPUT AS #1Sequence:FOR Bit = 0 TO 7PRINT #1, CHR$(255 - (2 ^ Bit)); ' Set one of 8 outputs high.SLEEP 1 ' Wait 1 sec between characters.IF INKEY$ "" THEN CLOSE : SYSTEMNEXT Bit

GOTO SequenceEND


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Power Supply - 12V @ 2A

Power Supply - Dual 15V


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Power Supply - Variable -- 1.2V To 25V At 4A

This power supply will provide you with variable voltage for your projects andanything else that needs it. It will provide from 1.2 to 25 Volts at 4 Amperes.


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Simple Power-Down Circuit

This circuit adds a power down function to analog I/O ports (for example, theAD7769 and AD7774). Moreover, the diodes ordinarily needed to protect thedevices against power-supply missequencing can be eliminated (see thefigure).

In the circuit, MOSFETs Q1 and Q2 switch the +5- and +12-V supplies,respectively, in a sequence controlled by two cross-coupled CD4001 CMOSNOR gates (U1C and U1D). The sequence in which power is applied is

important: The controlled circuits may be damaged anytime Vcc exceedsVdd+0.3V. Consequently, the NOR gates must be powered from a 12-V supplythroughout the power-down sequence.

Bringing the power down control high (+5V) applies power to the controlledcircuit by turning on all MOSFETs. Specifically, raising the power down bringsthe output of U1C low, causing capacitor C1 to discharge VOL exponentiallywith time constant R1C1. As the voltage on C1 falls, two events occur. First, itputs a negative gate-source voltage on P-channel Q1, turning it on. Second, itcauses output gate U1D to go high. With the output of U1D high, capacitor C2charges exponentially to VOH-about 12-V-applying a positive gate-sourcevoltage to turn on Q2. In the power down mode, the Power Down control isbrought low and the RC circuits and their delays work in reverse.Consequently, capacitor C2 discharges to the logic input of U1C before C1 cancharge. Hence, Q2 turns off before Q1.


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Sound Sensor

By using a microphone, high-gain amplifier (Fig. b), and detector-relay driver(Fig. a) a sound-detecting alarm system can be constructed. If you want alatching setup, make the dotted connections to the relay shown in Fig. a.


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Programmable Timer For Long Intervals

By using an RC oscillator and a programmable divider, this counter can run forhours. An interval oscillator runs at a frequency given by (see schematic):

f = 1 and R3~2R22.3 R4 C2

By using, for example, R4=390 K and C2 = 10mF and R2, the oscillator can runat 0.1 Hz. Divided by 65536, this is a cycle of approximately 655 000 s (182hours, slightly more than a week).


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Simple FM Transmitter

Running from a 9-V battery, this transmitter cam be used as a wirelessmicrophone with an ordinary 88- to 108-MHz FM broadcast receiver. Keep theantenna length under 12 inches to comply with FCC limits. L1 is 6 turns of #24wire wound around a pencil or a 1/4" form, with turns spaced 1 wirediameter. C6 is a gimmick capacitor of about 1 pF.

Date post:	04-Apr-2018
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ESQUEMAS DE CIRCUITOS ELECTRÓNICOS

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