Need very low cost flow switch for battery powered application - suitable for insertion in 1/2" water supply pipe.

My basic requirement is to wake-up a microprocessor when flow occurs in a water supply pipe. The pipe would be either steel or PVC. The size is in the 10mm to 1/2" range. Normally there is no flow but several times each day flow will occur and this is when I need to wake-up my (embedded) system to collect data.

Initial annual volume is in the range 1K-10K. The cost target for the complete sensor including pipe fittings and seals etc. is 7-8 Euro.

The ideal solution would be something like mounting a saddle bracket on the pipe. To drill a hole through the bracket into the pipe, and to insert some tiny solid state sensor into the pipe.

I've found some anemometers that are printed on ceramic thickfilm and coated with glass. These are low cost, very robust and they have excellent dynamic specs. The "only" problem is standby power consumption :-(

I'm now thinking about building a piezo electic element into a flap that vibrates when flow occurs and thereby generate a wake-up signal. I have a micro controller in the system and the ability to adapt to almost any kind of signals on the analog side.

Any references to part suppliers or alternative ideas are more than welcome!

Best regards,
Niels

 

If it needs to be rugged I would use a round magnetic with a hole in it and spring load it on a spindle in a PVC section of pipe. Outside of the pipe I would place (epoxy) a magnetic reed switch. When the flow starts it will move the magnet on the spindle and trip the switch. The reed switches are about $2 and the magnetic is about $3 at Radio Shack.

 

If you have any unused analog inputs (similar to the ATmel AVR series MPUs) then you might consider a thermocouple type approach similar to what its used for measuring a vacuum. Check out Sam's Laser FAQs web page.

Good Luck!

 

Niels

Checkout www.digikey.com. They have a variety of flow switches which would probably work for you. You can download theri catalog in pdf format.

Also go to www.sensorsmag.com, they will have lots of low end sensor manufactures listed.

Also since your looking for a simple flow switch and not a flow meter, way not just use a saddle bracket with a fine reed tied to a magnetic sensor, when water flows, the reed, moves, closes the magnetic sensor (you can even use a opto-interrupter), this goes to a digital input on the CPU. The DI takes a few milliamps (if that) and the opto device about the same. If you configure it to be closed - no light path - there is not current until the water flows and the current is only going to occur while the water flows. You can do a variety of methods here to solve this problem.

need more help drop me a line

[email protected]
technical consultants
MJH

 

Niels,

Can you use a pressure type switch, as I have a similar system...

Regards Charlie

 

Dear Sir,

M/s ACII-India manufactuers low cost flow switches.It needs Input 10-30VDC supply and you can get relay ouput 10A/230VAC.It is very cost economical option.If you need further information you can contact m/s ACII at [email protected] to Mr.Chetan Agrawal / 0091-22-34880887

Regards
Ravi