Moisture Sensors

i know a man who (for a fee) would design and make you one. to your specs too. i have used his serviecs in the past and im pleased. if your interested reply back to the group. steve

You could try these guys:

You could also build something based around this Honeywell chip:

Have you tried googling e.g. "moisture sensor circuit diagram"

I just tried and there a quite a few

I made one years ago, not much to them really

I think something suitable would be a "tensiometer". It's a cone of terra cotta, filled with water, and a pressure switch in a sealed lid. You stick it in the ground when it's as moist as you want it. The water inside reaches some sort of equilibrium with the damp soil via the permeable terra cotta. One sets the pressure switch to just trigger at that point.

Gardena makes some as accessories for their water timers. Probably overpriced, but readily available, so you can have a look.

Thomas Prufer

Aalmaecht thomas - you can build one for a coupe of quid ((a couple of quid * 1.4) Euros) - it's a project

"have a look at the Gardena ones to see how they designed theirs, and then roll your own" is what I should have said.

Come to think of it, I've seen drip waterers with tensiometers at the end: Terra cotta cone, and a thin tube that is opened or squeezed closed by some sort of plastic mechanical action. Used to water plants during holidays, fed from a raised bucket, that sort of thing. Called "Tropf Blumat" or something, ISTR, two quid at the most, next the cashiers in a pretty cardboard display in the garden center.

Ah, here we go:

Can't get that frame-ridden mess to display on my computer, is better...

Microswitch would make a nice digital output. Or use it as designed and measure the feed line pressure? flow?

Thomas Prufer