Random circuits

Here are some of over 800 projects from our free circuit diagrams database. For more, try browsing categories menu on the left.

Knightrider lights for model cars

This simple circuit drives 6 LEDs in 'Knightrider scanner mode'. Power consumption depends mainly on the type of LEDs used if you use a 7555 (555 CMOS version).... [read more]

4W FM Transmitter

Stabilised tendency of catering: Vcc=12~16V Frequency of emission: 88~108MHz Consumption: 100~400mA... [read more]

Digital Clock with MM5314N

Digital Clock with MM5314N... [read more]

An Expandable Transistor Based Burglar Alarm

This transistor based alarm features automatic Exit and Entry delays - together with a timed Bell Cut-off and system Reset. Along with the Exit/Entry zone - the basic alarm board has one Instant Zone. This will be adequate in many situations. However - the modular design means that it's easy to add as many zones as you like to the system. Details of a Four-Zone expansion module are provided.... [read more]

Capacitor Discharge Ignition Circuit (CDI)

The CDI ignition circuit produces a spark from an ignition coil by discharging a capacitor across the primary of the coil. A 2uF capacitor is charged to about 340 volts and the discharge is controlled by an SCR. A Schmitt trigger oscillator (74C14) and MOSFET (IRF510) are used to drive the low voltage side of a small (120/12 volt) power transformer and a voltage doubler arrangement is used on the high voltage side to increase the capacitor voltage to about 340 volts.... [read more]

Capacitive Sensor Circuit Diagram

The purpose of this circuit is to animate shop-windows by means of a capacitive sensor placed behind a post-card-like banner. The card is placed against the glass inside the shop-window, and the visitor can activate the relay placing his hand on the card, from the outside. Especially suited for toy-shops, the circuit can activate model trains, small electric racing cars, lights etc. Further applications are left at user's imagination. Adopt it to increase the impact of your shop-window on next Christmas season!... [read more]