I would like to replace the relay which triggers a water pump, with a relay which times out after, say, 10 minutes. And if it times out, it stays locked out until reset.

Needs to be 230v AC on both sides of the relay.

If it doesn't time out, the next time it's triggered it should come on normally.

I've spoken to everyone from RS to Farnell, and they have everything but that device. Making me wonder if I was using the wrong terminology.

I've got about 10cm by 12cm space to replace the standard relay currently inside the box (an ancient RS 348-403).

Thank you

(I noticed that the question warns me that "The question you're asking appears subjective and is likely to be closed". It either exists as a thing, in which case it has a particular name it's known by (eg: "no-retriggering timeout relay"), or it doesn't. I'm asking a question in the vein of "what's the name of the device which reduces voltage". Note that the question is clearly "what is the name of", rather than "what do you call" - the latter would indeed be subjective!)

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    \$\begingroup\$ Not everything needs to have a specific name or exist with a specialised function. Especially beyond basic building blocks, it would be be just "relay that can do X" just like "radio that receives band X,y and z" instead of a special name for each kind. A uc controlled relay board can be programmed to do whatever you want \$\endgroup\$ – PlasmaHH Sep 18 '18 at 16:54
  • \$\begingroup\$ Hmmm, what about if a capacitor was slowly charged, connected to a latching relay which would trigger at a certain voltage. The resistor, capacitor and trigger voltage being chosen to take around 10 mins. The capacitor would drain back as soon as the power was cut. A nice simple purely electrical solution? I'm not too au fait with mains voltage stuff, so someone might say no! \$\endgroup\$ – digitaltoast Sep 18 '18 at 20:16

It sounds as if all that you need to do is add a "Delay On" timer to your existing relay.

You will want to purchase a 2-pole timer relay with delay-on function. The reset button is normally-closed and is in series with the time-delay relay's coil. Pressing the reset button will cause the relay to turn OFF after it has latched ON.

One pole of the relay is used to latch-on the time-delay relay after it has triggered. The other pole disables the pump.

Ask if the above isn't clear and I'll add a schematic when I'm in front of my computer.

  • \$\begingroup\$ I kind of think I see where you're going with this, but how does this "lock out" the circuit once the "10 minute timeout" has been reached? \$\endgroup\$ – digitaltoast Sep 18 '18 at 17:38
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    \$\begingroup\$ The first set of relay contacts latches the time-delay relay closed. The easiest way to do that is to put those contacts in parallel with the main relay's contacts. That, obviously, will want to keep the pump running - but that's okay. The second set of contacts disables the pump. \$\endgroup\$ – Dwayne Reid Sep 18 '18 at 23:35
  • \$\begingroup\$ Ah, yes, of course - it all became clear when I slept on it. Woke up and wondered why I didn't think of it straight away! Thanks for that. I'll let you know what bits I ended up with! \$\endgroup\$ – digitaltoast Sep 19 '18 at 8:20
  • \$\begingroup\$ This? quasarelectronics.co.uk/media/ecom/prodpdf/… \$\endgroup\$ – digitaltoast Sep 19 '18 at 9:03

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