Saturday, August 21, 2010

Game Show Timers Schema electronic Circuit

Many people have expressed an interest in the game show timer from the "end user" viewpoint instead of the "hobbyist" viewpoint. These interested folks don't have much electronic assembly experience but they are highly motivated and are willing to give it a try in order to get the end result. It is with these people in mind that the following circuit was developed. This is my favorite and the one I recommend.

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 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

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