Game buzzer question

Discussion in 'The Projects Forum' started by benlin1994, Apr 29, 2013.

  1. benlin1994

    Thread Starter New Member

    Apr 29, 2013

    Sorry for the year long bump, but i have a relevant question.

    What is the practical purpose of the first main lamp? I feel like its only use is to lower the circuit's voltage once an SCR is triggered and stop current from going through the zener.

    Could the first main lamp be replaced with a resistor of equal value?

    Does the main lamp have an application when using the buzzer system? The way i see it, when someone buzzes in, their buzzer will alright light up so there is no need for an additional main lamp to light up.

    Also, will this circuit need to be turned off everyone time someone answers so it resets?
  2. crutschow


    Mar 14, 2008
    Yes, you can likely substitute a resistor for the lamp.

    The lamp is somewhat redundant but it alerts the moderator that a buttom has been pushed.

    Yes, the circuit has to be turned off to reset. That's one purpose for the battery switch (the other is to turn the system off). If you want to use a momentary switch to reset you could add a NC PB switch in series with the battery switch.
  3. Wendy


    Mar 24, 2008
  4. crutschow


    Mar 14, 2008
    With due deference Bill, I'm not sure I would call this a hijack. He asked a question about the circuit mentioned in that thread which rather seemed to be within the bounds of normal thread posts. Normally I consider it a hijack only if the poster is asking a somewhat unrelated question to the basic thread of the original post and I have called others out when they've done that.

    But obviously you have a more strict rule for what is considered a hijack. ;)
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
    I agree, this should be kept with the original. It is now completely out of context.
  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    Since it was a question related to my circuit in the other thread, I agree.

  7. #12


    Nov 30, 2010
    My 2 cents? The original thread is referenced by Bill, therefore this is a valid thread.
    I think benlin1994 did not "hijack" anything, but it was a case of necroposting with the rare quality that the OP is still active on this site. This being a (almost?) unique case of necroposting, it requires a judgement call by the moderators.

    Crutschow made a valid (helpful and true) answer and benlin's answer is also in post #6 of the original thread.
    I quote it here:

    With no responses, the low resistance main lamp, Zener and resistor in series allow enough voltage drop across the resistor to trigger an SCR. Once one SCR is triggered the main lamp and the contestant's lamp are placed in series across the 12V supply. Since that only allows ~6V across the contestants lamp and SCR, the 9V Zener will not conduct. There is then no voltage drop across the resistor and the other SCR's cannot be triggered. Elegant, isn't it!
    The caveat is that the SCRs be of the "non-sensitive gate" type.

    This explains (to people that are familiar with electronics) that the lamp in question makes a voltage divider and an indicator light, therefore it can be replaced with a resistor that allows the same amount of current as a contestants lamp, and the penalty is that there will be no indicator light that is not at a contestants' position.

    It's only my opinion, and sometimes I'm wrong.
  8. WBahn


    Mar 31, 2012
    Whether to split the thread or not is a judgement call that is up to the moderator. But, having said that, I read the first post and went, "Huhhh?????". Then I read crutchow's response and went, "Huhhhhhhh???????!!!!!!!" I then reread the first post wondering what the hell was going on and what I had missed.

    So might I make the recommendation to the mods that when you split a thread, edit the first post in the new thread and add a line at the very top that says:

    "Thread split from <link to original thread>"
    djsfantasi and #12 like this.