Cheap PID controllers

[Johnnyboy]

Hi,

I'm looking for a PID temperature controller for my HLT, and wonder if anyone has any experience of using the cheap Ebay ones from China? Are they worth a punt or not worth the hassle?

Any comments would be much appreciated.

John.

[keith1664]

I use one which controls 2 cheapy SSR's. One thing to look out for is which types of temp sensor it is compatible with, the really cheap ones tend to only work with k type thermocouples. Make sure that whatever you buy will accept a PT100 sensor.

A couple of pics of mine.





Alternatively if you only want to control one element one of these will work fine... and works out even cheaper as no SSR's are needed.

http://www.ebay.co.uk/itm/Digital-Tempe ... 43b0df0af2

[chris2012]

Would you be able to link to a PID the same as the one you used keith?

cheers

[Johnnyboy]

Cheers for reply Keith,

I have a thermobox with 2 x 2.75kw elements fitted, and was hoping to wire it so both are controlled so I can just switch on and forget about it.

John

[keith1664]

This one and it's the same seller.

http://www.ebay.co.uk/itm/Dual-Digital- ... 35be7e4e3c

They're also available from another seller on auction

http://www.ebay.co.uk/itm/PID-DIGITAL-T ... 1c297ee228

Don't forget to put heatsinks on your SSR's, the switches on the front of my box cut the control circuit to the relays so I can leave it all plugged in with the display on but no current goes through the elements.

[Johnnyboy]

Keith,

I take it from looking at your setup, that the one controller can run two elements, and that you can then switch the elements off independently once up to temp? If this is the case could you show me how it is wired?

Regards,
John.

[keith1664]

Yes it runs 2 elements, yes you can switch them off independantly, that bit is probably superfluous as the pid cycles them once up to temp, I just put them on so I can switch off the elements when emptying the hlt but still have the display working. You could just use one to turn the whole lot off.

I'll try to sort out a diagram for you... it could be a challenge as I don't have a scanner and I'm not sure what software I have I could draw one with!

[keith1664]

[keith1664]

For some reason the sockets have fallen off the end, but hopefully you get the idea.

If I never have to use MS Paint again I'll be a happy man!

[Johnnyboy]

Thanks Keith,

You did good as I would not have known where to start with drawing that on a computer and uploading it. Looks like my next brew project has just started.

Regards,
John.

[Wolfy]

As you can see in my build thread, I use a cheap Ebay "Sestos D1S-VR-220" PID.
A number of other AHB members use them, and the functions (but not the pin-outs when wiring it) are so similar to the (popular/more expensive) Auber-units, that you can use Auber's detailed instructions to setup/configure/run the PID (which is great because the brief badly translated instructions that come with the unit were impossible for me to follow).

[chris2012]

Wolfy - those seem to be sold with a K-type sensor (http://www.ebay.co.uk/itm/UK-Shipping-D ... 4ab54d53e9)
Could someone explain what the difference is between a PT100 sensor and a K-type sensor.

cheers

[keith1664]

A k type is a thermocouple - ie it produces a small voltage which varies with temperature. These tend to be use for high temperature applications. They tend to need recalibrating quite often as well.

A PT100 is a resistor who's resistance varies with temperature, they're more accurate at the temperatures we use.

[chris2012]

Cheers for explaining that.

I've just found a PT100 http://www.ebay.co.uk/itm/PT100-Tempera ... 2a12aef773

How come it has three connections though, if it's just a thermistor?

[keith1664]

That's something to do with minimizing the effect of the lead resistance.

Have a read of this