As more technical people wake up to the folly of trying to use simple resistive DC plant moisture sensors, it seems the Chinese have latched onto the idea of capacitive sensing…
And here it is, the sensor that is all over Ebay right now at am amazingly low £2 inc free shipping, that is until the UK rip-off artists get hold of it and at least double that price, which they’ve already done. If you are happy to sit over your plants waiting for a quiet “beep” – not quite so practical then, not to mention the constant supply of new battery pairs.
And definitely not to mention that the easily corroded batteries and active end are only an inch or two away from the waterproof, non-corrosive sensor end. Perhaps where the designers live the soil doesn’t move and there is no rain or snow.
Sadly, the only half-decent Chinese sensor that was around a couple of years ago has all but disappeared and definitely had a price-hike. Amazon will even sell you the same thing WITHOUT batteries or beeper for £12.99
However, the idea here is part way to being sound. Sadly we still see electronics at the complete mercy of creeping soil and the environment – utterly impractical as it stands so the user is left with DIY resin potting solutions or hope and prayer.
I just LOVE this variation: Bog standard 4-way cable is supposed to be “moisture resistant” ignoring the electronics which is openly exposed to the elements. Still, cheap enough and heading the right way but no indication of the output. “Impress your friends with real-time soil moisture data” – what? For maybe a couple of weeks until the rot sets in?
Take the above cheapy, take the connector off,put on a properly weatherproof cable and pot the top end in decent resin, THEN you might have something… however, lack of information in the ads leaves me wondering if this has some kind of digital output or are we needing a processor at the other end able to handle real time oscillating signals. Needs clarification but the chip doesn’t look sophisticated enough to me to do any kind of processing.
Ideally a digital signal indicating percentage dryness – bit from this circuit, I don’t think so,
These circuits are in a different world altogether to the crude DC PCB-strip-based sensors so very popular on EBAY but sadly still not in the right world for practical, unattended garden moisture monitoring and control.
We really need something better. The Mi Flora sensor is the ONLY thing I’ve seen that is even remotely practical and I got mine for £8 a couple of years ago. They have since seen a price hike to £9.53 from AliExpress, or, he says, laughing out loud, £20 from Amazon. Far from perfect but at least they don’t rot after a few weeks.
These devices are Bluetooth-based (which immediately raises range alarms and is why I don’t think, with 2 tears of experience that they are the end solution) and they give out sensible digital messages for moisture, light level and battery state. They do need additional treatment to make them properly waterproof. Potting is no good as you will need to change batteries at some point. I ended up using cling film, which was good for a year or so. I did not feel I could trust the battery readings.
Now, getting an internal Raspberry Pi to RELIABLY read a pair of external Bluetooth garden sensors, month after month in the winter – well, there’s another discussion.
Comments and especially ideas absolutely welcome. Some lateral thinking needed.