I need a circuit that flashs an led once quickly and then goes out. I have a circuit using a 2222 transistor and a photo resister that lights an led when the photo resister is dark. I need to add to this an led that flashs then goes out. 10 milli seconds or so when a beam of light is broken on the photo resister. It needs to reset quickly also. I really don't want to use a 555 timer, but would if it's the only way. I am wanting to control another project with this flashing led. Please email me your reply to; snipped-for-privacy@netzero.com Thanks RB
leds
Sep 12, 2007
1 Replies
Use a capacitor between the output of your current circuit to drive another transistor circuit. You'll need a resistor path to common on the other side of the capacitor so that it'll discharge for the next cycle. Selecting a capacitor verses the size of your load resistor will determine the on time state of the LED.. Assuming that your current single is now rather a fast transition? This should provide you with a short and sufficient pulse to drive another transistor which will drive an LED.
I think a 1 uf into a 1k ohm load should give you a very short pulse. use that signal to drive the base of a transistor that supplies your LED via the Emitter. (unity gain).
Personally, I use a 555 timer in one shot mode . that timer can drive the LED directly. but then again, You didn't want to go that way.
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