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This circuit uses the Holtek HT2884 IC to produce 8 different sound effects.... [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 circuit will let you know when something that should be kept closed - has in fact been left open. Attach it to a Fire-Door. It will allow you to pass through the door as usual. However, if it's left open for more than 30-seconds or so - the buzzer will sound.... [read more]

The LED traffic Light circuit controls 6 LEDs (red, yellow and green) for both north/south directions and east/west directions. The timing sequence is generated using a CMOS 4017 decade counter and a 555 timer. Counter outputs 1 through 4 are wire ORed using 4 diodes so that the (Red - North/South) and (Green - East/West) LEDs will be on during the first four counts. The fifth count (pin 10) illuminates (Yellow - East/West) and (Red - North/South).... [read more]

Like the first two Hijack Alarms - if a door is opened while the ignition is switched on - the circuit will trip. And after a few minutes delay - when the thief is at a safe distance - the Siren will sound. But this time the engine does not go on to fail automatically. Instead - it will continue to run until the thief turns off the ignition. Then the engine will not re-start.... [read more]

This circuit is a Logic Probe. It indicates the logic state of the node of any TTL logic circuit. To do that, we have to supply the probe with the same power of the circuit that we want to analyse: same Vcc and same GND. To check the logic level, we must connect the "Test" wire of the probe to the desired node of the circuit that we want to check.... [read more]