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7 segment display

Discussion in 'General Electronics Discussion' started by Springcone710, Dec 16, 2013.

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  1. Springcone710


    Dec 16, 2013

    I'm wanting to build a simple lap counter for my nephews scalextrics! I want it to be as simple as possible and if I can, I would prefer not to use adruino!

    Does anyone know if it's possible to make the 7 segment display count up and cycle back to 0 with just 1 switch? If so, how?

    I want to put the snap action switch in the groove on the scalextrics so that when the car passes the start/finish line, the cars leg that fits in the groove will press the switch and the 7 segment display will change!

    Thanks, chris
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Fairly simply, you could connect a counter with a bcd output to a bcd to seven segment decoder, and that to a seven segment display.

    The switch generates the clock signal which increments the counter. You'd probably wire up the reset line so you could push a button to reset the counter(s).

    The main problem is the switch. Switches bounce, so you would need to de-bounce it so that each press generated just on clock pulse, and therefore just increments the counter by 1.

    Chips you might be looking at are a 40106 (hex schmitt trigger) to be part of a circuit to debounce the switches, a 4511 BCD to 7 segment decoder/driver, and a 4510 BCD up/down counter.

    The use of a BCD counter eliminates problems with values 10 to 15 which can't be displayed on a single digit. This also allows you to cascade them for 2 or more digits.

    Oh, note that you need common cathode displays.
  3. ziin


    Dec 2, 2013
    It depends on what chip you prefer to use? Two of my favorite chips are Microchip and Arduino.

    If you want to use Microchip, I can give you more advice.
    Last edited: Dec 19, 2013
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