12V Latch Circuit Diagram

This circuit controls a solenoid by the operation of a single push-button switch. The circuit will supply loads of over 1 A and can be operated up to a maximum speed of once every 0.6 second. When power is first applied to the circuit, the solenoid will always start in its off position. Other features of the circuit are its automatic turn-off, if the load is shorted, and its virtually zero-power consumption when off.

12V Latch Circuit Diagram

Digital Electronic Lock Circuit Diagram

This Digital Electronic Lock Circuit Diagram shown below uses 4 common logic ICs to allow controlling a relay by entering a 4 digit number on a keypad. The first 4 outputs from the CD4017 decade counter (pins 3,2,4,7) are gated together with 4 digits from a keypad so that as the keys are depressed in the correct order, the counter will advance. As each correct key is pressed, a low level appears at the output of the dual NAND gate producing a high level at the output of the 8 input NAND at pin 13.

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Digital Electronic Lock Circuit Diagram

The momentary high level from pin 13 activates a one shot circuit which applies an approximate 80 millisecond positive going pulse to the clock line (pin 14) of the decade counter which advances it one count on the rising edge.

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A second monostable, one shot circuit is used to generate an approximate 40 millisecond positive going pulse which is applied to the common point of the keypad so that the appropriate NAND gate will see two logic high levels when the correct key is pressed (one from the counter and the other from the key). The inverted clock pulse (negative going) at pin 12 of the 74C14 and the positive going keypad pulse at pin 6 are gated together using two diodes as an AND gate (shown in lower right corner).

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The output at the junction of the diodes will be positive in the event a wrong key is pressed and will reset the counter. When a correct key is pressed, outputs will be present from both monostable circuits (clock and keypad) causing the reset line to remain low and allowing the counter to advance. However, since the keypad pulse begins slightly before the clock, a 0.1uF capacitor is connected to the reset line to delay the reset until the inverted clock arrives.

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The values are not critical and various other timing schemes could be used but the clock signal should be slightly longer than the keypad pulse so that the clock signal can mask out the keypad and avoid resetting the counter in the event the clock pulse ends before the keypad pulse. The fifth output of the counter is on pin 10, so that after four correct key entries have been made, pin 10 will move to a high level and can be used to activate a relay, illuminate an LED, ect. At this point, the lock can be reset simply by pressing any key. The circuit can be extended with additional gates (one more CD4011) to accept up to a 8 digit code.

Read :  Alarm Control Keypad Circuit Diagram

The 4017 counting order is 3 2 4 7 10 1 5 6 9 11 so that the first 8 outputs are connected to the NAND gates and pin 9 would be used to drive the relay or light. The 4 additional NAND gate outputs would connect to the 4 remaining inputs of the CD4068 (pins 9,10,11,12). The circuit will operate from 3 to 12 volts on 4000 series CMOS but only 6 volts or less if 74HC parts are used. The circuit draws very little current (about 165 microamps) so it could be powered for several months on 4 AA batteries assuming only intermittent use of the relay.

AM Receiver Circuit

Description:
This is a compact three transistor, regenerative receiver with fixed feedback. It is similar in principle to the ZN414 radio IC which is now no longer available. The design is simple and sensitivity and selectivity of the receiver are good.
Circuit Diagram

Notes:
All general purpose transistors should work in this circuit, I used three BC109C transistors in my prototype.The tuned circuit is designed for medium wave. I used a ferrite rod and tuning capacitor from an old radio which tuned from approximately 550 - 1600kHz. Q1 and Q2 form a compund transistor pair featuring high gain and very high input impedance. This is necessary so as not to unduly load the tank circuit.
The 120k resistor provides regenerative feedback,between Q2 output and the tank circuit input and its value affects the overall performance of the whole circuit. Too much feedback and the circuit will become unstable producing a "howling sound". Insufficient feedback and the receiver becomes "deaf". If the circuit oscillates,then R1s value may be decreased; try 68k. If there is a lack of sensitivity, then try increasing R1 to around 150k. R1 could also be replaced by a fixed resisor say 33k and a preset resistor of 100k. This will give adjustment of sensitivity and selectivity of the receiver.
Transistor Q3 has a dual purpose; it performs demodulation of the RF carrier whilst at the same time, amplifying the audio signal. Audio level varies on the strength of the received station but I had typically 10-40 mV. This will directly drive high impedance headphones or can be fed into a suitable amplifier.

Construction:
All connections should be short, a veroboard or tagstrip layout are suitable. The tuning capacitor has fixed and moving plates. The moving plates should be connected to the "cold" end of the tank circuit, this is the base of Q1, and the fixed plates to the "hot end" of the coil, the juction of R1 and C1. If connections on the capacitor are reversed, then moving your hand near the capacitor will cause unwanted stability and oscillation.
Finally here are some voltagee checks from my breadboard prototype.This should help in determining a working circuit:-
All measurements made with a fresh 9volt battery and three BC109C transistors with respect to the battery negative terminal.

Parts
Q1 (b) 1.31V
Q2 (b) 0.71V
Q2 (c) 1.34V
Q3 (b) 0.62V
Q3 (c) 3.87V

Author: Andy Collinson
Source: http://www.zen22142.zen.co.uk

Simple AC Power Current detector Circuit with LM1458

This circuit will detect power line currents of 250 mA or more without making electrical connections to the line. Current is detected by passing a line of alternating current through an inductive pickup (L1) as a screen diameter of 1 inch U-bolt wound with 800 turns # 30 – # 35 magnet wire.

The pickup could be made from rings of iron or other type of processor core that allows enough space to pass one of the AC lines through the center. Only one of the power line is the line or neutral must come from the center of the pickup to avoid the fields cancel.

I tested the circuit with a 2 wire extension cord that had separated the twin wires a small distance with an exacto knife to allow the U-bolt to encircle a single cable. The magnetic pick-up (U-bolt) produces about 4 millivolts peak for a series of alternating current of 250 mA, or AC load of around 30 watt

The signal from the pickup has grown about 200 times the output of pin op-amp 7, followed by the peak detected by diode and capacitor connected to pin 7. The second op-amp used as a reference point, which detects voltage increases above the drop pass.

The minimum mark required to cause the comparator output stage is a positive change of 800 mV peak around a power line 30-watt. The 1458 swing op-amp output in just a couple of times the ground so a voltage divider (1K/470) is used to reduce the voltage signal at about 0,7 volt.

An additional diode added in series with transistor base to ensure that off when the voltage op-amp is 2 volts. You can get a piece “of relay chatter if the AC load is close to the switching point so a larger load 50 W or higher recommended. The sensitivity can be increased by adding more becomes a pick-up

Simple 500W Audio Power Amplifier Circuit Diagram with Transistor

We take transistor MJL2194 and MJL2193 for drive output signal.so the amp has a capacity for enormous instantaneous current ability.

I think, it is useful for you to apply the circuit with your sound devices.

Circuit Functional
I use the -85 volt when the output current is supplied to the drive 350 to 340 very hot. Increase the output current, but it was too cold. The output to heat up faster than a normal open it. Sounds obvious, but sound quality is quite good.

I recomment it by turning out for the evening. If the drive is mounted on the metal part out.

I think simple. View full above, the observation that R 30 ohm then the voltage across the 0.86 V show that the new through its 29 mA if you add a file to / – 85 V, and suppose that the voltage across the component body. It was the same in both the R 30 ohm to get a very light 5 0.86 = 5.86 V and the current I will be 5.86/30 = 0.195 A = 195 mA, and the specification of mje340. mje350 get Ic (max) = 500 mA, so it is natural for it to heat up. Actually, it is not necessary to adhere to sync tr output should be interested in the following two tr power drive is better. For VR should be R300 .

1997 Audi A4 Air Conditioning System Circuit and Schematic Diagram on 1997 Audi A4

The following wiring diagram / scematic shows 1997 Audi A4 air conditioning system Circuit and Schematic Diagram which consists of A/C control head, footwell/defroster, flap motor and sensor, temperature regulator, motronic engine control module, interior temperature fan and sensor, digital outside air temperature/ transmission range selector lever display, sunlight photo sensor, A/C compressor speed sensor, outside temperature sensor, fresh air intake duct, fuse panel and instrument cluster, A/C compressor clutch relay, central flap motor and sensor, back pressure motor and sensor, center outlet temperature sensor, fresh air blower, coolant fan control thermal switch, coolant fan, and coolant fan control relay. 

For detailed information about 1997 Audi A4 Air Conditioning System Circuit and Schematic Diagram here (diagram 1 and diagram 2, source: autolib.diakom.ru)

Amplified Ear Circuit

Useful to listen in faint sounds, 1.5V Battery operation

This circuit, connected to 32 Ohm impedance mini-earphones, can detect very remote sounds. Useful for theatre, cinema and lecture goers: every word will be clearly heard. You can also listen to your television set at a very low volume, avoiding to bother relatives and neighbors. Even if you have a faultless hearing, you may discover unexpected sounds using this device: a remote bird twittering will seem very close to you.

Circuit Diagram:

Amplified Ear Circuit Diagram

        

Parts :

P1 = 22K
R1 = 10K
R2 = 1M
R3 = 4K7
R4 = 100K
R5 = 3K9
R6 = 1K5
R7 = 100K
R8 = 100R
R9 = 10K
C1 = 100nF 63V
C2 = 100nF 63V
C3 = 1µF 63V
C4 = 10µF 25V
C5 = 470µF 25V
C6 = 1µF 63V
D1 = 1N4148
Q1 = BC547
Q2 = BC547
Q3 = BC547
Q4 = BC337
J1 = Stereo 3mm. Jack socket
B1 = 1.5V Battery (AA or AAA cell etc.)
SW1 = SPST Switch (Ganged with P1)
MIC1 = Miniature electret microphone

Circuit Operation :

The heart of the circuit is a constant-volume control amplifier. All the signals picked-up by the microphone are amplified at a constant level of about 1 Volt peak to peak. In this manner very low amplitude audio signals are highly amplified and high amplitude ones are limited. This operation is accomplished by Q3, modifying the bias of Q1 (hence its AC gain) by means of R2.
A noteworthy feature of this circuit is 1.5V battery operation. Typical current drawing: 7.5mA.

Notes:

• Due to the constant-volume control, some users may consider P1 volume control unnecessary. In most cases it can be omitted, connecting C6 to C3. In this case use a SPST slider or toggle switch as SW1.
• Please note the stereo output Jack socket (J1) connections: only the two inner connections are used, leaving open the external one. In this way the two earpieces are wired in series, allowing mono operation and optimum load impedance to Q4 (64 Ohm).
• Using suitable miniature components, this circuit can be enclosed in a very small box, provided by a clip and hanged on ones clothes or slipped into a pocket.
• Gary Pechon from Canada reported that the Amplified Ear is so sensitive that he can hear a whisper 7 meters across the room.
• He hooked a small relay coil to the input and was able to locate power lines in his wall. He was also able to hear the neighbors stereo perfectly: he could pick up the signals sent to the speaker voice coil through a plaster wall.
• Gary suggests that this circuit could make also a good electronic stethoscope.

Source by : Streampowers

Inductance Meter Adapter Circuit

The inductance meter adapter circuit output is connected with a frequency meter and the inductance is calculated from the frequency. So, you will need a frequency meter and some calculation to get your inductor value. The circuit enables to measure inductance of the inductor which is the inductance to be measured. The operation of the circuit is built by a TTL square wave whose frequency relates to the inductance being measured. This the figure of the circuit;


How is the circuit work? The core of the circuit is the buffer colpitts oscillator(the first stage) which resonates with the unknown inductance to give a sinus wave of a particular frequency . The frequency of the sinus wave is a function of the unknown inductance and the four 1000pF C. The output sinus wave is amplified by the second transistor and is then rectified by the capacitor and diode combination that follows. The rectified sine wave now having only positive excursions is buffered by the third transistor and is then fed to the 74ls393. Counter IC which is configured as a divide by 256 counters. The output of the IC pin 6 and ground is connected to the frequency meter.

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