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Random timer

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groot_brak

New Member
I am in need of a very simple random timer. It should switch on at a random time interval and stay on for a random time, with set max off and on times. My specific case max off is 3minutes, and max on is one minute. But it is not that critical, as long as its random. Output is digital, i.e. on or off only. It must run continously with new random times every cycle.
 

Russlk

New Member
Noise is random. Use a Zener diode as noise generator, amplify the noise to logic levels and put it thru a bandpass filter whose frequency limits are 1/(the longest time) and 1/(shortest time).
 

ljcox

Well-Known Member
Another option is to use a pseudo random sequence generator.

This is a Shift Register with a XOR gate to generate the feedback signal.

I expect there will be examples on web sites such as "discovercircuits"

I not, I'll post one for you

Len
 

groot_brak

New Member
Thanx for the info Len, but it would be great if you post me that circuit as reference.

Russl, I'm not sure what you mean here. I need a random activated timer circuit, not random noise. Would be happy if you can provide me with more specifics.
 

ljcox

Well-Known Member
groot_brak said:
Thanx for the info Len, but it would be great if you post me that circuit as reference.

Russl, I'm not sure what you mean here. I need a random activated timer circuit, not random noise. Would be happy if you can provide me with more specifics.
The attachment shows a 4 stage Pseudo Random sequence generator. Note that this is not random timer, but simply generates pseudo random sequences. However, you could use it to design a random timer.

Load the outputs (some or all) of the SR into a binary counter and count down. The moment that the counter reachs Zero will be a pseudo random time from the moment the counter was loaded.

Len
 

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