DIY Pump Flow Sensor

[thekraken]

This one is for the electronics guys out there. I'm working on an Arduino based RIMS build, I wanted to put a flow switch on it as a safety to prevent the element from firing.

So far the easiest/cheapest idea I've come across is a capacitive sensor (also non-invasive and food safe). I've been playing around with the CapacitiveSensor.h library and a couple pieces of foil and have had good results. With nothing more than two small pieces of foil, a 1M ohm resistor, and some hook up wire I have been able to successfully detect the flow of water that I pour back and forth through a funnel.

Here is what I'm thinking: a couple pieces of copper foil would be glued to the inside of a pvc pipe, the silicon return hose from the RIMS would run through the pipe. This would be positioned high and vertically in such a way that liquid can't be present if the liquid isn't circulating.

Anyone have any comments to this method? Pitfalls, gotchas, etc...? I know false positives could be a problem with hands touching or getting to close to the sensor. Any way I can protect against that?

 

[ross_daly]

One thought I have is in regard to your layout. I feel that you could do something similar (but potentially more rugged) with a Tee. You could have a copper or stainless tube that was electrically insulated from the case and measure the impedance between those two. A bolt could be threaded into a 1/2" hole with tubing around it to insulate it.

 

[helibrewer]

Are you concerned with dry fire protection or only firing if there is flow?

 

[thekraken]

Both actually. I figure detecting flow covers both.

 

[ross_daly]

I don't think you are really measuring flow, merely conductance, right?

If you want to use that as a dry-fire protection, then I guess it would work. The point of rims systems and pumped systems is to get all of the bubbles out of the tubing, so whatever space you create will be flooded very quickly.

Secondly, don't put hot pvc in your beer. If you want to do this, get two barb splice connectors and use them in place of your foil pieces. Inline, one before the element, and one after the element.

 

[thekraken]

Yeah, not directly measuring flow and I don't really care to meter it either (at this point). I just need to rig up a switch.

The (c)PVC and the sensor wouldn't actually be in contact with the wort, the PVC is just a housing for the sensor and it would be slipped over the silicone tubing at the return to the MLT.