How to tell if a pump is running?

[FatalXception]

I need some ideas for a project- I have a submersible sump pump, and I want to monitor it. I have a depth sensor, which consists of one of those ultrasonic distance sensors mounted in a PVC pipe installed vertically into the sump pit, but I'd like to expand the project to be able to tell when the pump is running- I want to be able to graph start and stop times, as well as be able to set up an indicator while it is running. Can anyone point me to a project where this has been done, or even suggest how to do this? I can't open the pump because it is under water, so can't go by current flowing through the float switch. I could possibly use something that triggers by sound.... or I could also use something that clamps on to the power for the pump that uses some sort of inductor to detect current flowing through the wire. Any ideas?

[texy]

How is the power powered? AV or DC ?
You could attach a current clamp and monitor the reading, for example.

Texy

[rpdom]

Could you fit a water flow sensor in the output of the pump?

[ElEscalador]

Agree: simple flow switch. You could also add a water sensor at the discharge pipe...that might even be cheaper, if slightly more complicated.

[PiGraham]

It depends what matters to you. If you really need to know that the pump is moving liquid go for a flow sensor or differential pressure sensor. If you just need to know that the pump is energised just monitor the terminal voltage.

[woodystanford]

OK here is the answer. Simple fundamental induction.

Take a long stretch of single conductor telephone wire. Keep coiling it tightly around the power line of your pump's motor. Then get one of these:

http://www.ebay.com/itm/New-design-30A- ... SwirZTyJV7

(Interestingly, if you can wire the board directly in series with your motor, this might, MIGHT, work too).

Whenever the AC current is flowing it causes a current to form in the induction coil which can be read via ACS712->R-PI ADC. Software would have to debounce and condition it a bit but you would know programatically when the pump is on or off when you are done.

Throw it in a function when you are done:

Code: Select all

int IsPumpMotorON()

returning 0 if off, 1 if on. Then its up to you how you use it.

[woodystanford]

It depends what matters to you. If you really need to know that the pump is moving liquid go for a flow sensor or differential pressure sensor. If you just need to know that the pump is energised just monitor the terminal voltage.

I like the voltage idea thinking about it some more. See the cool thing about voltage and big motors is that voltage doesn't require the sensor to be connected in series (ie. it actually has to carry the full electric power of the motor through the sensor). Measuring voltage is very, very nice this way (it kind of just looks at the voltage...the sensor doesn't carry any electrical power).

I would do a really basic voltage divider based on 2 power resistors. Remember that AC's power is measured RMS. In layman's terms if you hook up a DC voltmeter to an AC line, you are always surprised that it comes back around 80V on a 120VAC line. That's because the waveforms of the AC have a MAXIMUM of 120VAC, but its actual effective voltage over time is about 80V. Bear with me as this will be important a bit later.

So what you do is you get your two power resistors (about 50 cents at mouser) and tap it in the middle and throw in a buff rectifier to clip the bottoms of the waveform. So 3 discretes total. Then, if your values are all right, it will be zero on your ADC channel when unpowered, and somewhere between 0.5 max and max when the motor is on. The way we are doing it outputs the RMS value on the input channel so put 80V into the resistor calculator on your input voltage and like 0.75 X max on output voltage.

The rest of it is academic...