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Cheapo PID Controllers for horticultural controls?
Reluctant_Gardener
Posts: 284
There are a number of PID controllers on the auction site market aimed at the hobbyist that are commonly used for brewing, kilning, fish keeping, egg incubation, small mammal warming at home. They do require some electrical and controls knowledge to wire, configure and operate safely.
Has anyone used the cheapos PID controllers for driving soil-warming cables for propagation benches?
(I worked in horticultural and renewables controls for a huge company, so used to using commercial controls, I just haven't used the cheapo ones)
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Frank. they work I have used a number for different projects over the years, as I'm sure your aware check that they can handle the current and correct voltage I always went for the next size up i.e.. if I want 2Amps I would get a 3A, 4A but never had any problems
Thanks. I'm not expecting much for ten pounds. If there are loud bangs they'll be in the greenhouse, not the house. The one I'm waiting for is supplied with a 70A solid state relay. One can't even get a decent ssr for GBP50.
forgive me , but what's PID?
Frank if its the ones from that well known auction site the no problem had loads from them and all been fine they do smaller SSR versions 70A that's a big load
Hostafan1
The PID controllers are every where - temperature, motion, flow controllers - and available in analog and digital forms. It helps get your output (velocity, temperature, position) where you want it, in a short time, with minimal overshoot, and with little error.
: P -Proportional, I - Integral, D - Derivative. These terms describe three basic mathematical functions applied to the error signal , Verror = Vset - Vsensor. This error represents the difference between where you want to go (Vset), and where you're actually at (Vsensor). The controller performs the PID mathematical functions on the error and applies the their sum to a process (motor, heater, etc.) So simple, yet so powerful! If tuned correctly
Tuning a system means adjusting three multipliers Kp, Ki and Kd adding in various amounts of these functions to get the system to behave the way you want.
That's it now my brain hurts I'm off to bed
thanks for the explanation Gardeners Boy, but I'm none the wiser.
I'll get my coat.
Hostafan1
They can be used as a very accurate thermostat and also other applications where
you need very close control.
thanks again TGB. looks way too techy for me.
I received the PID Cxer "Rex C100 +40A SSR [not 70A my mistake] +K type T/C" Friday morning and it took less than half an hour to hook up (most of that looking for tools, crimps and butyl flex to strip). I'm quite surprised something so cheap works so well. I was looking for the catch as ratings sometimes don't mean much with cheapo OEM stuff. It's mounted in a polystyrene box just now until I get into town to the wholesaler for an ABS box and a new coping saw blade.
I went to Maplin in my neighbourhood for a heatsink for the relay but they'd nothing the right size. There was a fly tipped television set outside a block of flats on the way home so got the PCB out of that and will desolder/unbolt the heatsinks and some components tonight. There's hardly any load on it so at full duty the thermal plane on the back of the SSR is barely above ambient.
Far cheaper than the stats that are sold to go with soil-warming cables and with a long-tailed thermocouple one can site the controller well away from misting and other hazards.
I'll probably get a couple more for other processes around the house and garden.
The chilli seeds which I thought had either boiled with uncontrolled heat or rotted when there was insufficient heat have germinated.
Well put, The Gardeners Boy BTW.