Random circuits

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

Simple Logic Probe

This simple logic probe has both LEDs on with no signal at the input but due to the nor gates connected to the probe, indicates correctly when a high or low signal is present. It also works correctly for pulse trains. Normally both LEDs are forward biased and therefore on, powered by the 12V supply. When a logic "high" is present at the probe, IC1a's output goes low sending IC1b's output high. This turns off LED1 but forward-biases (and turns on) LED2. Conversely, a logic "low" at the probe will send IC1b low, turning LED1 on and LED2 off.... [read more]

LEDs or Lamps Sequencer

The purpose of this circuit was to create a ring in which LEDs or Lamps illuminate sequentially. Its main feature is a high versatility: you can build a loop containing any number of LEDs or Lamps, as each illuminating device has its own small circuit.... [read more]

Dancing LEDs Circuit Diagram

The basic circuit illuminates up to ten LEDs in sequence, following the rhythm of music or speech picked-up by a small microphone. The expanded version can drive up to ten strips, formed by up to five LEDs each, at 9V supply. IC1A amplifies about 100 times the audio signal picked-up by the microphone and drives IC1B acting as peak-voltage detector. Its output peaks are synchronous with the peaks of the input signal and clock IC2, a ring decade counter capable of driving up to ten LEDs in sequence.... [read more]

1.5 Hour Lamp Fader (Sunset Lamp)

The sunset lamp comes on at full brightness and then slowly fades out over 1.5 hours time and stays off until power is recycled.... [read more]

Brightness Controller Circuit For Small Lamps and Leds

This device was designed on request; to control the light intensity of four filament lamps (i.e. a ring illuminator) powered by two AA or AAA batteries, for close-up pictures with a digital camera. Obviously it can be used in other ways, at anyone's will.IC1 generates a 150Hz square wave having a variable duty-cycle. When the cursor of P1 is fully rotated towards D1, the output positive pulses appearing at pin 3 of IC1 are very narrow.... [read more]

IR Remote Control Jammer

Don't like your little brother's TV channel selection? Hate the volume your wife sets the stereo at? Want to just annoy someone? This circuit does all that and more by jamming most IR remote signals. The circuit releases a flood of pulsing IR light that confuses the reciever by corrupting the data stream.... [read more]