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555 timer. Keep a LED off for 60 seconds than on for 2 seconds

Sean-Paul Carey

New Member
I need to use a 555 timer (astable) mode to keep a LED off for 60 seconds than on for 2 seconds, a bit smoke detectors that turns a red LED on about every 60 seconds for 1-2 seconds then repeats. If it is easier to turn the LED on for 60 seconds and off for 2 seconds it won't be problem as I can invert pin 3 from the 555. I'm using a breadboard. a circuit diagram would be greatly appreciated.
 

crutschow

Well-Known Member
Most Helpful Member
Here's the LTspice simulation of a 555 astable circuit that should do what you want:
The Off time is determined by R3 and the ON time by the parallel value of R3 and R4, in conjunction with C2.

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dr pepper

Well-Known Member
Most Helpful Member
If your project is battery powered then a 7555 will use a bit less juice.
 

crutschow

Well-Known Member
Most Helpful Member

gary350

Well-Known Member
I like this circuit with 2 diodes & 2 resistors it makes math very easy. There are several variations of this. Variable resistors lets you fine tune the circuit or set it to exactly what you need while circuit runs. Variable resistors lets you change it to a different low time or high time separately. It has been about 2 years since I experimented with this circuit I don't remember why pin 7 is not used. It is possible to have an off time of about 20 minutes.

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