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I'm looking for a way to check the air-flow from an aquarium air pump. I need something that can test whether air is flowing or not and I'm not bothered about measuring flow speed. The air will be flowing through a pipe but if required I can have the sensor on the end of an additional pipe just used for measuring.

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Did you consider a barometric sensor deployed inside the pipe? The pressure should be higher when the pump is active.

  • The issue is that the sensor is very big and the pipe is 1/4" – connersz May 29 '15 at 15:54
  • As it was commented below, you can use various means to make the measurement, either by duplicating the path or by using a mechanical sensor, however there is also a more creative approach. If you know (you can measure it once) the profile of power consumption of the pump, you can measure it over time and verify that it behaves as it should. This of course is an indirect measurement and implies trust that the system is not leaking air after the pump. But it might be less invasive. – Igor Stoppa May 29 '15 at 20:09
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Grab yourself something like this

enter image description here

Butcher it to get inside it, and add three small magnets to the fins (should be simple enough - just keep it balanced). Then glue it all back together again.

Add a hall effect sensor to the outside, and Bob's your uncle.

Or, since the principle of that unit is so simple, you could make your own from scratch.

  • Even simpler: if that thing is transparent, one can add a photodiode/photo transistor pair around it and detect pulses (interrupts) on the transistor. – Igor Stoppa May 29 '15 at 20:04
  • Good idea :) I hadn't thought of that obvious one. – Majenko May 29 '15 at 20:21
  • Love that the linked page header says "enema flow indictors" (sic) - is that in, or.. out? – Mark Williams May 30 '15 at 21:45
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Flow sensors tend to be expensive. However, there are many pressure sensors that provide a simple analog voltage input and others with easy to use digital interfaces. As Igor Stoppa points out, these can be used to infer flow. Some can be purchased with tube ports that allow the user to mount the hose directly to the sensor. This would only require a "T" connector and some additional hose to connect to the air pump.

Aquarium air pumps may be pulsatile. So be sure to use an average pressure.

Average Pressure:

  • above a certain point may indicate blockage
  • between certain values indicates correct flow
  • below a certain value indicates no flow

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