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  1. #181
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    Re: Help re-creating a replica movie prop

    Hi,

    I hope everyone is well. I haven't been able to work on this project since January 6th, but I'm still here. To recap: I achieved accurate pitch and duration using both potentiometers, but still can't get the switch wired in properly. Currently, the only way to produce a tone is by removing the ground end of the jumper that goes from pin 1 to ground on the second 555, and touching it to the diode at the very beginning of the circuit. Any thoughts? I think if I can get the switch properly wired, this circuit might be ready for a pcb.

    Thanks,
    John



  2. #182
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    Re: Help re-creating a replica movie prop

    Welcome back!

    Pin 1 is the ground pin on an NE555 so it should always be connected the negative (GND) rail. If the tone appears when you connect in anywhere else it indicates you have a wiring error somewhere. Wiring it to a different voltage could damage the IC as it might result in lower voltages on other pins than the ground pin and force current 'backwards' where it shouldn't be going. However, with the values in this particular application it is very unlikely that damage will occur.

    Pin 4 is the reset that is used to turn the tone on and off again. You should find that connecting pin 4 of the second 555 to + turns the tone on and grounding it turns the tone off. The purpose of the first 555 is to make pin 4 go high for the duration of the beep then go low again, effectively doing what linking it manually does but on a timer.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



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