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Looking for a budget latching relay which needs manually resetting once triggered

tl;dr version:

I'm looking for a mains-voltage simple latching relay which will simply open a circuit as soon as it's triggered, and then stay latched open until reset either physically, or by some kind of push-button trigger.

Without going into the tedious details*, I need to cut out a 300 watt inductive mains-powered water pump if it has been running for more than 10 minutes. 

After a few phone calls to RS and others, it became clear I needed to make this out of two components, delayed-on timer and a latching relay. I found the timer at

Now I just need the latching relay. So many choices, mind-boggled, not quite sure which one.

I'm in the UK, and this is a home hobby project, so suggestions of "just simply use this £395 PCL" wouldn't be so helpful!

And optionally, I'm also looking for a cheap mains-voltage buzzer which will just go "beep beep beep" when energized. Again, struggling to find that.

Thank you.

(*OK, if you REALLY want to know the story behind why I want to do this, read this. It gets tedious...



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October 3, 2018 07:37

Hi there,
I had a look at the story on diynot and I honestly think your best solution(s) were provided on the plumbing thread.
If robustness to failure is your main intent, then the suggestion to [firstly increase the size of your overflow pipe and] use two series-wired float switches – or a lower switch to turn the pump on and upper switch (backed up with a ball-cock if you really want security) to turn off the pump is the way to go. These both have the benefit of being simple. What you are proposing, although a bit ‘techie’ is much more expensive to implement and statistically likely to fail a long time before the simple solution.
I tell you this as an electronics engineer who loves electronics but also has a strong appreciation of how (complex) electronics fail in the field.

0 Votes

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