The speed of an automobile can be indicated by detecting the pulses generated by the ignition system and causing an LED to light. The circuit utilizes a quad NOR gate IC chip. Two of the gates are configured as a one shot multivibrator which produces a fixed duration pulse each time the primary circuit of the automobile ignition system opens the circuit to the ignition coil. The other 2 gates are used as buffers which provide an accurate rectangle pulse. As the number of pulses per second increases, the voltage fed to the base of of the NPN transistor becomes high enough to cause it to...

This alarm circuit is based on two 555 timers. The alarm will sound your car horn if anyone opens the car door while the circuit is armed. The timers will allow you to leave the car without sounding the horn. To turn the circuit on S1 must be closed. To set the alarm, open S2 ( it is normally closed ) this will give you about 5 seconds to get out and close the door. The exit delay time is set by R1 and C1. If anyone opens the doors for more then two seconds the horn will sound until power is removed from the circuit. The 2 second time is set by R2 and C2. If you open the door, you must...

The Car Temperature Gauge is basically the same circuit as the [url=http://www.circuitdb.com/circuits/id/237]Car Voltage Gauge[/url] circuit with some minor changes to the input circuit. This circuit will display the water temperature to 1 degree resolution. Copyright 1999 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url][i:3a54839816][/i:3a54839816]...

The Car Voltage Gauge is based on 3 parts. The input circuit is an Analog to Digital Converter (IC2 CA3162E). The purpose of this chip is to sample an analog voltage and convert it to a decimal value which is read by a Display/Decoder Driver (IC1 CA3161E). This chip will turn each seven segment display on through the driver transistor Q1 - Q3. The power is derived from the car and is converted to 5 volts by the 5 volt regulator. The circuit works as follows: The 10uf capacitor is charged up by the cars voltage. Its value is then read by IC2 and a decimal value of that voltage is provided to...

The circuit is drawn for measurement of acceleration from -1000 mg until +1000 mg. It can be placed in kantra'n the car and be supplied from the sheath of electric lighter. The circuit includes one indicative LED and a screen LCD. [url=http://www.circuitdb.com/download.php?fileID=199]Click here to see the schematic[/url] [url=http://www.circuitdb.com/download.php?fileID=198]Click here to see the ADXL202 connection[/url] The measurement of acceleration becomes with the use of IC from Analog Devices, the ADXL202. The particular element contains 2 autonomous vertical between them...

[b:e43bc460fa]Intro & disclaimer[/b:e43bc460fa] For all you guys out there that want a fading dome light (aka courtesy light aka theatre lighting) without having to pay for one, you can build your own. I have attached the schematics and you can build it for a few bucks given that you don't have any spare components lying around otherwise it can cost you absolutely nothing. Of course you can rip some parts from your TV, CD player, radio, etc., but I'm not responsible for the damage you cause this way [b:e43bc460fa]The way it works[/b:e43bc460fa] I won't bother you with technical...

The lamps are faded by varying the duty cycle so that higher power incandescent lamps can be used without much power loss. The switching waveform is generated by comparing two linear ramps of different frequencies. The higher frequency ramp waveform (about 75 Hz.) is produced from one section of the LM324 quad op-amp wired as a Schmitt trigger oscillator. The lower frequency ramp controls the fading rate and is generated from the upper two op-amps similar to the "fading eyes" circuit. The two ramp waveforms at pins 9 and 1 are compared by the 4th op-amp which generates a varying duty cycle...

In the circuit above, a quad voltage comparator (LM339) is used as a simple bar graph meter to indicate the charge condition of a 12 volt, lead acid battery. A 5 volt reference voltage is connected to each of the (+) inputs of the four comparators and the (-) inputs are connected to successive points along a voltage divider. The LEDs will illuminate when the voltage at the negative (-) input exceeds the reference voltage. Calibration can be done by adjusting the 2K potentiometer so that all four LEDs illuminate when the battery voltage is 12.7 volts, indicating full charge with no load on the...

The limitation of car supply voltage (12V) forces to convert the voltages to higher in order to power audio amplifiers. In fact the max audio power x speaker (with 4 ohm impedance) using 12V is (Vsupply+ - Vsupply-)^2/(8*impedance) 12^2/32 = 4.5Watts per channel, that is laughable... For powering correctly an amplifier the best is to use a symmetric supply with a high voltage differential. for example +20 - -20 = 40Volts in fact 40^2/32 = 50 Watts per channel that is respectable. This supply is intended for two channels with 50W max each (of course it depends on the amplifier...

This circuit uses the popular and easy to find LM3914 IC. This IC is very simple to drive, needs no voltage regulators (it has a built in voltage regulator) and can be powered from almost every source. [b:7bd0f5dac2]This circuit is very easy to explain:[/b:7bd0f5dac2] When the test button is pressed, the Car battery voltage is feed into a high impedance voltage divider. His purpose is to divide 12V to 1,25V (or lower values to lower values). This solution is better than letting the internal voltage regulator set the 12V sample voltage to be feed into the internal voltage divider simply...

This circuit is designed primarily for the situation where a hijacker forces the driver from the vehicle. If a door is opened while the ignition is switched on, the circuit will trip. After a few minutes delay - when the thief is at a safe distance - the alarm will sound and the engine will fail. [b:14688bdea7]Notes:[/b:14688bdea7] Before fitting this or any other engine cut-out to your vehicle, carefully consider both the safety implications of its possible failure - and the legal consequences of installing a device that could cause an accident. If you decide to proceed, you will need to...

This circuit features exit and entry delays, an instant alarm zone, an intermittent siren output and automatic reset. By adding external relays you can immobilize the vehicle and flash the lights. [b:dbd4232981]Notes:[/b:dbd4232981] The alarm is "set" by opening Sw1. It can be any small 1-amp single-pole change-over switch - but for added security you could use a key-switch. Once Sw1 is opened you have about 10 to 15 seconds to get out of the vehicle and close the door behind you. When you return and open the door the buzzer will sound. You have 10 to 15 seconds to move Sw1 to the "off"...

[b:456985bfcc]Bar-mode LED-cluster sequencer Can drive up to 16 clusters[/b:456985bfcc] [b:456985bfcc]Comments:[/b:456985bfcc] This circuit, designed on request, allows up to 16 LED clusters illuminate in bar-mode sequence. LED sequencing will start when the Brake pedal is pressed (or Turn Lights are switched-on) and, when the last cluster illuminates, all LED clusters will remain steady on until the Brake pedal is released or Turn Lights are switched-off. [b:456985bfcc]Notes:[/b:456985bfcc] * R5 and D1 are optional: they could be of some utility in monitoring the sequence...