recycle counter with random range

Thread Starter


Joined Mar 30, 2011
We have an electronics box powered by 110VAC thru an IEC input connector. The unit does not draw more than 1A. We would like to have this box go through repeat cycle chamber testing.

The unit will be powered ON for a time frame anywhere from 3 minutes to 7 minutes (desire a random time in this range). Then power is turned OFF to our box for a fixed time of 30 seconds. After the 30 seconds, the box is powered up again for another 3 to 7 minutes random time. This process will repeat continuously.

I have an AC solid state relay module that has a 0-10Vdc control input. Therefore, we'll only need the desired trigger controller circuit to go to the AC Relay module that has the 0-10Vdc control input.

Any help or circuit diagrams would be much appreciated. I am also open to having a set time frame of, for example: 5 minutes, instead of the random range of 3 to 7 minutes ON time....should it be difficult to generate a random time range.


John P

Joined Oct 14, 2008
If you have a PC with a parallel port, you can run it off that and never need to build any hardware except wiring up the plug. Assuming someone there can write some simple software, you can get this going very quickly, and random intervals wouldn't be a problem.


Joined Jul 7, 2009
This would be straightforward to do with a small PIC processor and it can generate pseudorandom sequences to use for the timing. Use a 5 volt wall wart for power and you can drive the solid state relay with the PIC if it requires less than 25 mA of current; if more, then use a small signal transistor.

If you want to do it yourself, buy the PICkit 2 Starter Kit from Microchip (a nice, small package for $50) and go through the lessons. You'll know all you need to know and you can find PIC assembly programs on the web for the pseudorandom number generator.

Warning: you will find lots of things you can do with these things besides... :p