Home > Circuits > Lottery Number Generator
Modified:21:15, 22 October 2013
This circuit produces a number from 1 to 49 using 7 segment displays. Pressing the run switch enables the astable formed by IC5 to run at about 400Hz. The square wave output is fed to a BCD counter (IC1) and the 4-bit output to a 7 segment decoder (IC2). The carry out from the units counter is then the clock for the tens counter.
When the tens counter reaches 5, (binary 0101) the out put from the NAND gate goes low which is inverted and used to preset the counters. It is necessary to 'Reset' rather than 'Preset' the counters since the lowest number is one not zero. The preset inputs for the units are therefore set at 0001 (P0=1, P1-3=0). The tens counter could be reset as well as preset as it still starts on zero.
The circuit was constructed using CMOS IC's so any voltage from about 4.5v to 12v can be used, with the only effect being the brightness of the LED displays. The 330ohm resistors may get a little warm and care should be taken not to exceed IC2,4 maximum wattage. The circuit draws a fair amount of current so using a PP3 is not recommended. AA's or C sizes would be longer lasting.


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Designed and Written by Phil Townshend 2008
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