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Here is a really simple game show timer designed with the beginner in mind! The power source is an ordinary 12 volt lantern battery or battery pack made up of C or D cells. The lamps may be ordinary flashlight bulbs; the prototype uses 750 mA Krypton types (KPR112) with wires soldered directly onto the bulbs. The control devices may be just about any non-sensitive gate SCRs
Game Circuits - schematic

or triacs with a current rating of a few amps. Avoid SCRs that trigger with 100s of microamperes; you want a gate trigger current of a few mA or else you will have trouble with more than one light coming on at once. A low value resistor, perhaps 470 ohms may be added from gate to -12 volts to reduce false triggering. SCRs are shown and triacs may be substituted by connecting MT1 to the negative battery terminal and MT2 to the lamps. In fact, the two types of devices could probably be mixed if that is what the junk box has to offer! (But not sensitive gate types!) The zener is an ordinary 9 volt, 1 watt type like the 1N4739. The 100 ohm resistor may be any type with a rating of 1/8 watt or more. The reset/power button is an ordinary toggle switch and the pushbuttons are any convenient normally-open type. The entire circuit may be built into one box with two wires running out to each contestant`s pushbutton switch or the SCR, lamp, and switch may be in a remote box for each contestant with three wires running back to the base unit. Many more than three contestants may be added by repeating the pattern. Here is what you see: The three lower lamps are soldered directly to the MT2 terminals of triacs (anodes if SCRs are used). These particular triacs (RCA T2710) come with an integral heat sink connected to MT2. The gate leads (on the left) connect to the pushbuttons (red wires) and the other end of the pushbuttons all go to the...



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