On 9/6/2013 8:59 PM, Guv Bob wrote:
"Jim Mueller" wrote in message b.com...
On Fri, 06 Sep 2013 09:57:57 -0700, Guv Bob wrote:
snip
Thanks Jim. I have no experience with 555 timers. Where would I find a
basic circuit for this application using a 555?
Here's a data sheet: http://www.ti.com/lit/ds/symlink/lm555.pdf. It has
a number of generic circuits. What you want is a monostable circuit. It
can be set up to trigger from power-on or from a separate signal. Can
you modify the example circuit yourself or do you need help?
--
Jim Mueller
To get my real email address, replace wrongname with dadoheadman.
Then replace nospam with fastmail. Lastly, replace com with us.
Thanks, Jim, that's a big help. I'm afraid I do need more help. Someone also mentioned needing a diode. I'm pretty lost at the component level.
The diode would be placed in parallel with the relay coil, if you needed
relay, which you don't.
If it helps, the application is to energize a small LED for approx 5 seconds when 12VDC is applied to the input. After 5 seconds the LED should go off even though 12VDC is still on the input.
That should be easy to do with a comparator and a simple RC circuit.
I don't have the LED current draw, but it's very small - probably on the order of 10ma.
Most LEDs will operate fine at 10 mA; typical maximum current is 20-30
mA steady-state.
Many thanks for this help!
Bob