Little Help?

[Ozymandias]

What I am doing:<p>I am making a quiz buzzer system, suitable for any amount of players, which both lights an LED and buzzes when a player pushes a button.<p>I've done all the lockout, and I've got me a UM3561 to generate the Police Siren (that's no problem).<p>What I'm looking for help with is getting the time for the buzzer, and the lockout.<p>1)There's a rail on my circuit that goes low when a button is pressed, and I was wondering how to get this to trigger a 555 response. <p>2)The response is that the siren chip needs to be turned on for a set time (I know how to set a 555 time) and then the buzzer turns off, and won't be able to turn on again until the reset button on the panel is pressed (it breaks the power supply to the whole circuit. A one-shot 555 circuit is no good, as the contestant can just keep pressing the button over and over again. Not ideal, I'm sure you'll agree.<p>Any help much appreciated,<p>~Ozy

[philba]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Ozymandias:
What I am doing:<p>I am making a quiz buzzer system, suitable for any amount of players, which both lights an LED and buzzes when a player pushes a button.<p>I've done all the lockout, and I've got me a UM3561 to generate the Police Siren (that's no problem).<p>What I'm looking for help with is getting the time for the buzzer, and the lockout.<p>1)There's a rail on my circuit that goes low when a button is pressed, and I was wondering how to get this to trigger a 555 response.
<hr></blockquote><p>so you are asking how to trigger low? use an inverter.<p> <blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr><p>2)The response is that the siren chip needs to be turned on for a set time (I know how to set a 555 time) and then the buzzer turns off, and won't be able to turn on again until the reset button on the panel is pressed (it breaks the power supply to the whole circuit. A one-shot 555 circuit is no good, as the contestant can just keep pressing the button over and over again. Not ideal, I'm sure you'll agree.<p>Any help much appreciated,<p>~Ozy<hr></blockquote><p>Use a flipflop like the 74HC74 with preset/clear.<p>[ February 18, 2005: Message edited by: philba ]</p>

[Ozymandias]

Thanks m8<p>In fact, I don't know why I didn't think of that before. I mean, the first design I attempted rotated around flip-flops.<p>Ta muchly, I'll let you know how it goes,<p>~Ozy

[Enzo]

Your quiz buzzer would be called a first event detector. For some insights into that, go to www.edn.com and search for "first event detector". WHen the results come up, where it says look for more results, click on "design ideas"<p>Ther is a nice little article about it. The thing in the article is self resetting, timed out by an RC. The LED for a particular player will stay on for the period determined by the RC. The LED could just as easily be an opto-isolator running a triac for regular 120VAC lamps. In any case, run an OR from the outputs to control your buzzer, and any LED that goes on will also trigger the buzzer, and when the LED times out, the sound quits as well. <p>I made something similar, but used a manual reset - it suited my needs. And I had no buzzer to contend with.<p>A suggestion, whatever sound you have it make, try to make it a pleasant one. A raucous buzzer is funny a time or two, but will get real tiring if it keeps going off for any length of time. AFter a half hour of buzzers going off, we will be cringing waiting for the next buzz.