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Connecting this circuit to the battery of your vehicle, you will always know at a glance the approximate voltage available. An indication of battery voltage is useful to the motorist for monitoring the battery's capacity to deliver current, and as a check on the efficiency of the dynamo or alternator. Threshold voltages of the Leds are set by means of two Zener Diodes (D6 & D10) plus two further Diodes wired in series (D4, D5 and D8, D9 respectively) adding a step of about 1.3V to the nominal Zener voltage.... [read more]

This electronic game pits a human player against the ‘machine’. The opponents use a common ‘game token’ and take turns moving along a path by one, two or three steps, and the winner is the first one to reach the goal exactly. Incredibly enough, this simple version of the ‘123’ game can be built without a microcontroller, and it’s almost impossible to beat.... [read more]

This two-transistor white noise generator has a surprising feature – about 30dB more noise than the more traditional designs. Q1 and Q2 can be any small-signal transistors with a beta of up to 400. The reverse-biased emitter-base junction of Q1 provides the noise source, which is fed into the base of Q2. Q2 forms a simple amplifier with a gain of 45dB. The improved output level is due mainly to the inclusion of C1, which provides a low-impedance AC source to the noise source while not disturbing the DC bias of Q1.... [read more]

This circuit is a 73 MHz Hallogene Lamp Radio-Controlled. The purpose of it is to control the power state of a hallogene lamp by a remote control.... [read more]

This is simple transistor based motorcycle alarm. The circuit features a timed output and automatic reset. It can be operated manually using a key-switch or a hidden switch. By adding an external relay, it will set itself automatically - and/or immobilize the machine - every time you turn-off the ignition. It's easily adapted for a 6-volt system - so it will protect your "Classic Bike"... [read more]

Readers who do not care to modify the power supply of an old PC into a suitable halogen power source (see our April 2006 issue), may find the present design a welcome alternative. The circuit does not need any changes to the power supply. It allows the halogen lamps to be initially powered from the 5V rail of the supply via RE2, so that they are preheated. Subsequently, they are powered from the 12-V rail via RE1, while at the same time the 5-V rail is disconnected.... [read more]