Re: TI-H: Circuit/component help
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Re: TI-H: Circuit/component help
> This isnt calc related (directly), but it seems most stuff on here isnt....
has anybody else been deleting on first sight the threads on [OT] whatever
and TI-H: linux..? Don't answer that.
> I need a circuit that when a momentary volatge is applied it holds a
> voltage for something else. I'm designing a trip circuit system and
> when someone trips the laser beam a voltage spike go and turns on a
> light for as long as the lasers path is blocked. I'm looking for
> something that is tripped so the light stays on until someone resets the
> circuit...
Sounds like you want something that will go on and stay on until it is
manually reset. I can think of two options: a flip-flop IC or an SCR.
I don't remember exactly how the flip-flops work, but they come in a lot
of packages (DIP14 for example) and can be set up such that the first time
a signal goes active the device will latch ON (or OFF, if you prefer) and
will ignore all additional signals until a reset happens. I haven't done
that for a while, though, so I don't remember exactly how to go about
doing it. A drawback to this is that you must have a nice clean 5 vdc
supply for the flip-flop, and then you'll need interface stuff for
whatever circuitry you want it to control.
The SCR method should be pretty easy: SCR stands for Silicon Controlled
Rectifier. It's basically a diode, but it's got a gate in addition to the
anode and cathode. When a signal arrives at the gate, it allows current to
pass through the diode. Current will continue to flow, even after removal
of the activation signal, until the current is interrupted. So you set up
the circuit to give a pulse of whatever length to the gate of the SCR, and
put a normally closed momentary switch in series with the diode. When the
activation signal goes up, current flows. It continues to flow until the
SPST(n.o.) switch gets depressed.
--
Greg Hill
greg-hill@bigfoot.com
www.comports.com/link
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