Low pressure sensor

Why does it have to like water? Shouldn't be difficult to arrange the connecting tube to have air in it. If vapor bothers you, put a loop in it with some oil to isolate the wet and dry parts.

Go to a washing machine repairer and get a water level sensor from a washing machine. Even new water level pressure units are only $20 for some machines. Find a dumped automatic top loader washing machine and get one for nothing.

Are these variable or switches though? If they're variable they might just be perfect, thanks.

Michael

Thanks, I'm willing to give it a try. I had considered this but was not sure it would be a problem or not.

not eactly cheap

ah forget it,

Well, silicon chip, if I remember it correctly, had a such a project quite a few years but, but I think it used a sound transducer to measure the distance. Might be easier.

have you worked out the difference in pressure between a full and an empty tank?

Yes, they are variable with a small screw on the back. Make sure you re-seal the screw so they don't leak air.

I'll see if I can google it.

Around 1.4 psi or 0.1 bar.

But I presume they don't have a variable output with a variable pressure, that screw just sets the point at which it switches. My washing machine has a dial you can set fill volume but I bet the dial is directly connected to the screw you're talking about.

Michael

I really want to be able to see the level from my PC. A bit silly I know. :-)

Michael

Is your water tank easily accessible/visible?, if so then a proper dial gauge is a much better and simpler idea. Bunning's sell this exact one for like $20-$30:

Dave.

some have an input so which adjusts the switching level. it may operate at 240V though.

I think it'd be fun to make one that works on the principle that water around an insulated conductor changes the capacitance

----+--- vcc | +-[1M]--------|--------+ | | | | +--------+ | | | | | | | . . . .|. . . . | | | . VCC(8) . | | | . . | | +--RES(4) OUT(3)--+--> measure frequency | . 7555 . +-------TH(6) DIS(7)--- | . . +-------TR(2) CV(5)-- C1 | . . ===== . GND(1) . | . . . .|. . . . | | +-------------+ | ---+-- gnd here C1 is a length of figure-8 cable (or several lengths) sealed at the bottom running from top to bottom of the tank.

There are some sensors around for recording pressure at the level of human breath. Last time I looked, about 10 years ago, they were around $10 bare. Just connect one of those up to ADC and feed it into your computer. Simple serial or parrallel feed.

Use a webcam.

In the past people have several times asked here for something similar. A project in the April 1994 issue of Silicon Chip has been mentioned a couple of times - it used an ultrasonic transducer to detect the level.

The UK magazine EPE featured a Water Level Gauge project in September

Andy Wood snipped-for-privacy@trap.ozemail.com.au

On Sat, 28 Feb 2009 21:37:26 +1100, "Michael C" put finger to keyboard and composed:

PIC-Based Water Tank Level Meter Parts 1 & 2:

The design includes a telemetry version.

Circuit board:

Datasheet for pressure sensor:

- Franc Zabkar

I know people who've used a webcam for that. Cooler than just some indicator on your screen. And if you position it right (i.e. gauge to one corner of the image) you can also use it as an outdoor weather and/or security cam etc.

Dave.

Frogs? mossies? other insects?

Nice idea but I would really like to be able to make automated decisions based on the amount of water in the tanks, eg water the garden more if the tanks are full. I think I'll just go with the jaycar sensor as it's easily available and not too expensive compared to other costs. I think the silicon chip article was based on this same sensor. Thanks everyone for suggestions.

Michael