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Circuit to flash a few times, then stop, then repeat cycle

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rfd22932

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Need a simple circuit to flash an LED a few times, then stop, then repeat the cycle. Does anyone have a shematic to show this? Thanks!
 

kchriste

New Member
Forum Supporter
Need a simple circuit to flash an LED a few times, then stop, then repeat the cycle. Does anyone have a shematic to show this? Thanks!
You could probably use a 4017 and 555 for this. It depends on the timings. How many is "a few times"? How long is "stop"?
 

rfd22932

New Member
Blink 3 or 4 times with a half to one second interval, then off for 3 seconds or so, then start all over again. Pretty sure it can be done with just 555 (one or dual?).
 

kchriste

New Member
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You could do it with a dual 555 (LM556), but sometimes it may flash 3.5 times instead due to RC circuit tolerances and drift. Adding a 4017 instead of the 2nd 555 would ensure that exactly 3 equal flashes in a row occur.
 

Boncuk

New Member
Hi,

here is a circuit as suggested. The timer output frequency is 2Hz. D1 through D3 make a diode network to have the LED blink every second clock pulse. The counter then coninues to count 9 and resets from pin11 to pin15 (which is actually not required since the IC starts automatically at the count of zero after count 9)

You might want to use shorter breaks between three flashes. Use Q6(pin5), Q7(pin6) or Q8(pin9) connected to pin15 to achieve shorter breaks.

For a clock freqency of approximately 1Hz use 6.8MΩ for R2

Boncuk
 

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