Re: NEED HELP! Simple DC circuit

DaveK wrote:
What do I need? 555/556 Timer? Flip-Flop? I have a basic
understanding of electronics, but most likely would not be able to set
up this circuit without a schematic. At this point in my education,
telling me what to do, without a schematic, probably wouldn't help me.
Believe me I'm trying as hard as I can to learn this stuff. I'm
really getting hooked on it, but I'm not even close. I've played with
the timers but that's about it. This circuit doesn't seem that it
would be very hard for someone who knows what they are doing, but then
again what do I know? Thank you for your time and any help would be
greatly appreciated.

I have a 4.5vdc (battery operated) circuit with three momentary
switches. The 1st two switches are in series and when closed power a
buzzer for the amount of time that they are both closed. The third
switch when closed powers a LED. What I want to happen is when the
third switch is activated, but not continually closed (momentary
switch) it will trigger power to the LED and continue to stay on till
one or both of the 1st and 2cd switches are closed once again. The
third switch may never need to be on, but if it does it will need to
stay on till one of the other two is closed.
TThank you for your time and any help would be greatly appreciated.

you need an R-S flip flop. (R = Reset), (S= Set). they create a latching effect to the Q outputs.
just about any FF with R&S with work.

Or, you can use 2 Transistors of NPN types.
Look here, this is what you can do with transistors which is
a Monostable set/reset flip flop.

http://ourworld.compuserve.com/homepages/Bill_Bowden/page9.htm




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Real Programmers Do things like this.
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