Hello,
can anyone please point me to a circuit that I can use to stretch the on time of an LED when the on pulse is small? I have a push botton that I want to press momentarily and see a longer (say 1 second) illumination of the LED.
Many thanks in advance.
Gaz
Look at monostable configuration in the applications section of a 555 data sheet. Trigger pulse produces one output pulse - applying that to your switch and LED should be obvious.
Or use a Sherman tank where a BB gun would do, and use a microprocessor. In cases where you have a lot of complexity already, and/or have a micro in there already, it makes sense. If this is all you want to accomplish, it's a bit overkill.
This concept is synonymous with "pulse stretcher":
A 555 can source 200mA:
Look at page 5 of this link:
A monostable multivibrator is basically a pulse stretcher with a fancy name. Look at the other application circuits. Lots of fun stuff you can do with a
555.Regards, Bob Monsen
Thinking about this again, you might not have "a LED". There are some gizmos that they put on e.g. candy displays.
These are a plastic housing containing a stack of 3 button cells and a device that looks like a LED. What that is is a clear package that houses a LED
*PLUS* an on-board chip that flashes the LED. If you look at it closely with a strong magnifier, you can see the chip.There is nothing you can do to change the flash rate of this thing.
On Fri, 15 Feb 2008 18:38:33 GMT in sci.electronics.basics, Ecnerwal wrote,
Isn't that overkill? He's talking about keeping a LED on long enough to see it, not a Precision Timer job. Wouldn't a real designer be able to do that with, say, a capacitor and a single transistor?
You've got to be joking.
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