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Crappy PID Controller
- This topic has 10 replies, 6 voices, and was last updated 2 years ago by
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Hi there,
I happened to buy a pair of PID controllers off Ebay that were described by Dave in one of his videos as ‘crappy’ ones. And they are. 🙂
I’m talking about you, REX-C100FK02-M*AN.
Below you see a photo of the side of it. It is a RELAY type PID controller and this means there are relays inside.
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Having relays inside is unnecessary as we are using Solid State Relays (SSR) with it anyways. (Photo below)
(Imagine having a switch for your light switch in a room, too many switches)
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The initial problem is that the SSR shown above needs up to 32V DC, to operate. This means it requires a separate energy source.
As we don’t want to use more adaptors, we could get rid of the inner RELAY, which by the way is powered by 12V DV.
12V DC is enough to power the SSR, so we just do a bit of soldering as the guy says in the video to turn this RELAY PID controller into an SSR type everyone else on this forum has:
But the relay in this PID can handle 750W load so if you’re using less than that in band heaters you can connect it directly and don’t need the SSR.
Being mechanical, the relay won’t last as long as the SSR as it will be continually switching, but it may last long enough, or if not just buy a less crappy PID next time.
Also I just watched the video, something to be aware of (the guy on the video doesn’t mention this, even though he may be aware of it).
The way he has rewired the PID, pin 5 will be at +12V the whole time, and pin 4 will alternate between floating and grounded. This will work for the SSR he is using, but would not work at all if the SSR shared a logic ground with the PID, or if it was driving some other type of device where you would expect the 12v signal to switch.
NB. I’ve never used this type of PID and I’ve come to this conclusion just by looking at components on the board he does not mention (the position of the freewheel diode and transistor are a giveaway). He mentions on the video a forum, but not if it’s this one, so I don’t know if he can confirm this.
Also I wouldn’t use bare links like he does, a pair of 1/4W 330Ω resistors will protect the PID if you connect it wrong.
I got a cheap PID + Thermocouple + SSR combo for about $30 in Amazon, and so far I have zero complaints about it https://www.amazon.com/gp/product/B00AE25716/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
@xxxolivierxxx,
sure thing, I bought Inkbird like the one from the link as well and have no complains now)
@jegor-m, hope you can give me some advice!I have a rex c-900 controller (output:relay) and a AC-input SSR (15 amps) and I manged to power two band heaters (2.5 amps). However, I am trying to find out if I can power 4 band heaters (5 amps) with this configuration. My doubt is because the specs sheet of the controller does not states the amperage of the contact output relay (somewhere I read it may be 3Amps at 250V) however I opened the controller and a noticed that the output relay inside states 10 Amps at 250Vac. Do you thing it is safe to power the 4 band heaters without modifying the controller?
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Are you using the SSR? Wouldn’t the PID just be switching a low current input to the SSR?
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