Car battery condition checker
This circuit uses an LED and 4081 CMOS integrated circuit. The variable resistor sets the voltage at which the LED turns on. Set the control so that the LED lig...
Headlight delay unit
This circuit will operate a car"s headlights for a predetermined time to light up the driveway or path after the driver has left the car. SQl is pushed and Q2 i...
Car battery monitor
Warning light (LED) indicates when battery voltage falls below level set by 10 K pot...
Ice warning and lights reminder
This device will tell a driver if his lights should be on and will wam him if the outside temperature is nearing zero by lighting a LED and sounding a buzzer9 V...
Windshield wiper controller
This circuit provides complete speed control over car"s windshield wipers. They can be slowed down to any rate even down to four sweeps per minute...
Auto battery current analyzer
This op-amp analyzer can measure the current drawn by any device in a car. The analyzer works by measuring the very small voltage that develops across the batte...
Windshield wiper control
Here"s a good way to set windshield wipers on an interval circuit. Only two connections to the car"s wiper control, plus ground, are required...
High speed warning device
A1 amplifies and regulates the signal from the spark coil. A2 converts frequency to voltage so that its output is a voltage proportional to engine rpm. A3 compa...
Tachometer
An electrical signal taken from the low tension side of the distributor is converted into a voltage proportional to engine rpm and this voltage is displayed on ...
Bargrapk car voltmeter
The LM39X4 acts as a LED-driving vol-tometer that has its basic maximum and minimum readings determined by the values of R2 and RV2. When correctly adjusted, th...
Courtesy light extender
Most car door switches are simply single-pole switches, with one side grounded. When the door is opened the switch grounds the other line thus completing the li...
Speed alarm
Pulses from the distributor points are passed through a current limiting resistor, rectified, and clipped at 4 volts. Via Q1 and the diode pump, a dc voltage pr...
Gasoline engine tachometer
This tachometer can be set up for any number of cylinders by linking the appropriate timing resistor as illustrated. A 500 ohm trim resistor can be used to set ...
Car battery monitor III
The circuit is quick and easy to put together and install, and tells you when battery voltage falls below the set limit as established by Rl (a 10,000-ohm poten...
Car auto-dimmer
This circuit switches car headlights to the low beam state when it senses the lights of an on-coming car. The received light is very low level and highly direct...
Ignition monitor strobe
Figure A shows the circuit of a direct-trigger timing light. The trigger voltage is -taken from the car's ignition circuit by a direct connection to a spark plu...
Delayed headlights circuit
This circuit keeps an automobile's headlights on temporarily. It also will turn the lights off, even if you forget to flip the light switch. The circuit's shut-...
Ice warning alarm 12V
The circuit warns car drivers when the air temperature close to the ground approaches 0°C, thereby indicating possible formation of ice on the road surface. ...
Headlight circuit
When the lights of an on-coming car are sensed by photo-transistor Ql, things get going. Sensitivity is set by the 22-megohm resistor, R5, to about half a foot-...
Car temperature indicator circuit
The circuit is used to indicate two different water temperature trip points by turning on LEDs when the temperatures are reached. The circuit is constructed aro...