Low-power water level alarm

[pokmo 0]

Hi

 

I'm planning to build a low-power water level alarm which can last for at least 4 months on continuous usage. I've found a schematic using the 555 timer but it'd use some 30mW. I wonder if it'd be a good idea to use MSP430, put it to sleep and raise an interrupt when a certain pin is short by water's conduction. Is water conductive enough to wake up the MSP430?

 

Any thought appreciated.

 

Thanks

[cubeberg 540]

I believe so - assuming your connections are close enough.  You do need to consider corrosion/oxidation as a potential issue.  One alternative would be to use capacitance as well instead of a straight on/off - assuming you don't wake up too frequently - you should get good battery life out of that as well.

[USWaterRockets 57]

Why not put the entire thing inside a sealed enclosure with a tilt activated switch? One end of the enclosure is tethered to the bottom of the water filling zone and the length of the tether is adjusted so it tilts the enclosure when the water level is higher than the tether. You could put the whole thing inside a common plastic food container and it could run for years off a coin cell.

[pneumatics 2]

There are several industrial water level detectors that work based on conductivity of liquid. It's proven. I think it may be little difficult if you use interrupt alone,since chance of false alarms are more. If you are using interrupt which lpm your have to use? Will polling be more efficient if response time required is low?

 

Sent from my Redmi 3S using Tapatalk

[LIJsselstein 9]

When you only need one switch level, use a float switch. Cheap, easy, super low power, and it works . Put your mcu in lpm4 and wait for the switch interrupt to wake you up. If you need reliability in debris filled water or need to protect it against animals or vandalism then mount the switch in a perforated pvc tube.

[trumps2000 1]

Conductivity is the way to go. Simple and effective. I bought this off of tindie:

 

https://www.tindie.com/products/hbouzas/esp8266-03-wifi-wireless-water-sensor/

 

I modified it for low power and attached to an msp430. I planned to make it wireless but have been fighting with the cc2500.

[abecedarian 330]

There is also ultrasonic sensing as an option.