Newest circuit diagrams

Temperature-controlled 12V dc Fan

Suitable for computer cooling fans. LED motor speed indicator

Doorphone Intercom

A simple Intercom made with a single transistor and low power audio amplifier LM386. The circui uses 8 ohm speakers, which also double as a microphone.

Loudness Control

When listening to music at low volume levels, bass and treble frequencies are attenuated more than mid frequencies. This loudness control alters the frequency response curve to correspond roughly with the equal loudness characteristic of the ear. The circuit shown, is for a single channel, so for a stereo system, two such units should be built. This circuit has a boost of 13dB at 20Hz and approximately 9dB at 20kHz.

FM Receiver

An FM regenerative receiver using a single FET and one audio amplifier IC

Long Range FM Transmitter

With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometres.

Voice Operated Switch

This circuit is a voice operated switch (VOX) and designed for audio frequencies within a commercial telephone bandwidth of 100Hz to 3000Hz. Input amplitude is sensitive down to 10mV and the output comparator can drive a relay or interface to micro processors and TTL switching between 0 and 5Vdc.

IR Remote Control Extender Mark 4

An Infra Red wired Repeater circuit to control appliances from a remote location

Temperature Monitor

A simple op-amp circuit that will trigger a relay when a preset temperature is reached. Please note that there is no hysteresis in this circuit, so that if the temperature changes rapidly, then the relay may switch rapidly.

Guitar Amplifier

10W Old-Style ultra-compact Combo. Two inputs - Overdrive - Treble-enhancement

Automatic Intruder Alarm

This is a simple single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays and a timed Bell/Siren Cut-Off. It's designed to be used with the usual types of normally-closed input devices such as - magnetic reed contacts - micro switches - foil tape - and PIRs.