VM188 : Getting a smaller pulse time?


I’m want to use the VM188 to provide a delayed start to a washing machine equipped with a start button. The idea is to program a delay of say 3 hours then make a small pulse that simulates a push on the washing machine’s start button.

My problem : the smallest time interval for the pulse is 1 second, which is not accepted by the washing machine’s controller : it ignores such a long push.

Basically I think the only (easy) way to get a smaller pulse (I’d need 0,5s) is to modify the code.

Is the PIC’s memory protection activated ? Do you provide the source code anyway ?

Or : Do you see any other Velleman kit that would do this ?



Velleman never releases the source code so I think this will not be possible. Or you can experiment with a relay and capacitor.


What’s you idea more precisely ?


A relay with in series with the coil a capacitor with parallel resistor.
When sending power, the capacitor will let pass the current because it needs to get charged. This current is for a short time enough to energize the coil of the relay. After a short while the capacitor gets charged and current lowers so coil of relay is not energized anymore. Resistor (high ohmic value) is to discharge the capacitor afterwards.


I see your point. So I’ll cut the track between the transistor and the coil and insert a R//C network.

It’s a long time since I experimented such a trick. Do you’ve any advice for starting values ?

I would do it outside the pcb … much safer. No, no values, please experiment.


220uF did the trick, thanks !

Now, I discovered that my washing machine put itself in a kind of sleep mode, requiring the user to push the start button one more time to get it out of sleep and then (one second later) a second push to make it actually start up :frowning:

I guess I should learn how to program this PIC and reprogram it with my own software…


Super! Thanks for the feedback!

Too bad a second problem arised. I think it will be easiest to program your own PIC indeed. It is not that difficult if you program in a higher language because there have different delay possibilities.


Some months later, I succeeded recreating the software from scratch. It wasn’t that easy, since the Program and Data space of this particular version of the PIC isn’t big and I quickly ran into memory problems.

However, it now works, at least on simulator.

Feel free to grab the software on https://github.com/pagaille/PVM188 if anyone is interested.

Happy to read that you have succeeded.