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Speaker Mic Circuit
Speaker Mic Circuit
June 5, 2013

This circuit takes an ordinary loudspeaker and allows it to be used in reverse, as a microphone. [more]

High Quality Intercom
High Quality Intercom
June 5, 2013

A very high quality intercom, which may also be used for room monitoring. [more]

LED Torch
LED Torch
June 5, 2013

The LED Torch is based on a 7555 timer running in astable mode (do not use an ordinary 555). A white LED (Maplin order code NR73) produces 400 mcd light output, which, when focussed, can illuminate objects at 30 metres. [more]

LED Torch
LED Torch
June 5, 2013

Based on the Maxim MAX660, designed to power three 3mm/5mm white LED's from 3V (1.5V min) , intended for replacing incandescent bulbs in small torches. [more]

Xenon Strobe
Xenon Strobe
March 1, 2011

This is a very simple strobe circuit which I have not seen anywhere else. My inspiration came from a strobe circuit that was in a school fire alarm buzzer - the kind that has a built-in strobe light on top. [more]

LED Flasher
LED Flasher
March 1, 2011

Based on "Application Notes" for LM317LZ, flashes an LED using the phase-shift principle. [more]

Infra Red Link
Infra Red Link
March 1, 2011

A basic Infra Red Link for audio communication for distances upto 3 metres. [more]

Digital Combination Lock
Digital Combination Lock
December 10, 2010

A multiple input combination loack using CMOS counter IC's. Flexibility and code change is allowed by changing output connections. [more]

Electronic Doorbell with Counter
Electronic Doorbell with Counter
December 10, 2010

This circuit uses a synthesized sound chip from Holtek, the HT-2811. This reproduces the sound of a "ding-dong" chiming doorbell. Additionally, the circuit includes a CMOS 4026 counter display driver IC to count your visitors. [more]

Switch De-Bouncer
Switch De-Bouncer
December 10, 2010

This circuit will remove the transient spikes and contact bounces from a non-latching push button switch. [more]

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