You need to put a small pressure vessel following the pump. It's obviously pressure cycling. It is extremely common with caravans etc. The electrical solution is actually fixing the symptom, not the problem. Fix the problem.
One of the problems with circuits where we don't understand exactly what they're measuring, is whether the circuit will work when bodged into place. The title sounds more promising than the actual circuit implementation.
Darlington pairs have a response speed. I had some set up years ago, for usage as hobby logic probes, and their input sensitivity, you could detect a logic signal with 100 megohms in series. But the probe was also a bit slow to respond, which means if the circuit was sensing a
50Hz field, it won't be amplifying the signal completely. Only a fraction of the available response will be there.So that's what happens when you go "too cheap". For example, how would that circuit perform, if the DC supply came from a wall adapter, and the LED was on an extremely long pair of wires ? Dunno.
Doing stuff like this is much more reasonable, if you have a local electronics store. We lost ours, and it kinda stifles my creativity. I like to be able to visit the store and cobble together some substitutes and make something.
Paul
Generally that Darlington configuration is far too sensitive and non linear to be of practical use.It will pick up broadband noise and eventually switch hard on.
A "Voltstick" or one of it's brothers: a contactless voltage indicator, held in a to-be-determined place with cable ties, so that it lights up when the pump is energized?
Thomas Prufer
It sounds like pressure variation on the input can result in cases where it is inadequate to properly turn the pump "off", so it runs, builds pressure, and turns off again. Pressure falls and the cycle repeats.
A small water hammer shock arrester on the output side of the pump may fix it - allowing a small amount of pressure to be "stored" in the compressed gas in the arrester.
Well yes - it seems the problem would be better sorted by stopping it getting into the cycle state in the first place, rather than reporting the situation after it has got there.
I would go for something like this:
This device would be pretty robust, the only unknown is the response time, where an LED being lit would be instant. However it would indicate when the pump is stalled and being turned on and off through some internal temperature cut-out.
Only issue is the householder most likely won't notice what the pump's doing. Plus I wouldn't buy anything from Amazon.
Yes, they have and yes there is (insufficient water etc) The problem as I see it is that once the pump gets stuck in its hysteresis loop or whatever, the only way to stop it is the Microsoft approach (turn it off and turn it back on again).
It's just a matter of knowing when this is happening, in order to turn it off and on again, if one is hearing impaired.
Nick
I'm currently (sorry!!!!) looking into several of these suggestions so thanks for all of them. Just for clarity, to the best of my knowledge, the pump never stalls: it's just switched on and off very rapidly.
Thanks,
Nick
Also how a pipe runs is often important if the problem seems like an oscillation, could be air in a bit of the pipe which is bent along its length. I've seen this in a gravity fed shower, not sure how it would interact with a pump. Brian
It probably has an induction motor, and so has high inrush. That pulsing current profile ought to be easy to sense (and in a non contact way if required)
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