Raspberry Pi: Sensing Mains Voltage

[SteamyTea]

Does anyone know of a cheap way to do this with a Raspberry Pi.

All I want to know is when a pump is on or off, I don't need to know the current or the voltage.

I am thinking that I could use a contactor, wired in parallel with the pump, and just sense when it is closed with a GPIO ports/pin.

It would be nicer to use a non-invasive method such as a CT clamp, but not too sure how to set that up as a simple detector.

 

Thoughts anyone?

Edited January 24, 2017 by SteamyTea

[Guest Alphonsox]

How about a neon or LED across the switched supply and a light sensor ?

[SteamyTea]

I had thought of that, but I can get a relay for a tenner, and it should be pretty easy to wire in (not actually seen the pump yet).

 

An alternative is a small PSU that can drop down to 3VDC and sense that voltage.  Not sure how to wire it into the Raspberry Pi as it will not be the same as the unit powering the Raspberry Pi.

Maybe connect all the neutrals together.

[Onoff]

http://m.ebay.co.uk/itm/142228782611?_trksid=p2141725.m3641.l6368

[SteamyTea]

Oh, that looks useful, thanks.

[Steptoe]

You could alternatively for a flow sensor on the pipework ,    ?

[Guest Alphonsox]

1 hour ago, Steptoe said:

You could alternatively for a flow sensor on the pipework ,    ?

 

Just pointed Terry at one of these on another thread

http://www.ebay.co.uk/itm/Flowmeter-Switch-Pulsed-Water-Beer-Flow-Meter-Sensor-1-2-/400713718471?hash=item5d4c661ac7:g:WkUAAOSwNSxVRftI

 

Should directly interface to the Pi GPIO

[Steptoe]

45 minutes ago, Alphonsox said:

 

Just pointed Terry at one of these on another thread

http://www.ebay.co.uk/itm/Flowmeter-Switch-Pulsed-Water-Beer-Flow-Meter-Sensor-1-2-/400713718471?hash=item5d4c661ac7:g:WkUAAOSwNSxVRftI

 

Should directly interface to the Pi GPIO

It would indeed, 

Good find,

 

[PeterW]

Just check its WRAS compliant as it may be food safe but that won't count ..!

 

But as @JSHarris says, will they check ..?!

[TerryE]

Why not just an accelerometer to detect the vibration / hum whilst running.  Then you don't need to touch the mains voltage.

[Steptoe]

Thought about this,

The easiest way would simply be a relay wired I'm parallel to the pump, with the outputs going to the RPi GPIO

That's the simpilest method, and no complicates code or anything else for the Pi

Exactly as you said in the OP @SteamyTea