Random circuits

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

Video amplifier

Video amplifier with LM359N... [read more]

Mosfet TESTER

This is a variation on the astable multivibrator. Circuit was recently developed to test for N-mosfets(the power kind e.g irf830)... [read more]

Mini Audio Analyzer

This analyst is, a sensitive instrument, in the frequency changes and width of a acoustic signal. Thus the brightness of LED that turns on each moment of is proportional signal width, while the colour of proportionally frequency.... [read more]

An Expandable Multi-Zone Modular Burglar Alarm

This circuit features automatic Exit and Entry delays and a timed Bell Cut-off. It has provision for both normally-closed and normally-open contacts, and a 24-hour Personal Attack/Tamper zone. By using the Expansion Modules, you can add as many zones as you require; some or all of which may be the inertia (shock) sensor type.... [read more]

FM Transmitter Bug

This small transmitter uses a hartley type oscillator.... [read more]

Stablised Power Supply With Short-Circuit Indication

Here is an efficient 4-stage stabilised power supply unit for testing electronic circuits. It provides well regulated and stabilised output, which is essential for most electronic circuits to give proper results. The circuit provides an audio-visual indication if there is a short circuit in the PCB under test, so the power supply to the circuit ‘under test’ can be cut-off immediately to save the valuable components from damage.... [read more]