Playing with a PID
In the process of building the electric kettle, I bought a PID (proportional-integral-derivative) controller to control the kettle temperature. Since this came from Amazon and had Chinglish directions, I figured I should get it out of the box and test it.
The controller is a little 1.75″ x 1.75″ (45mm x 45mm) square. The screen has two displays, one for the temperature, one for the set point. There are also four buttons, SET, <<AT, up, and down.
I threw together a setup that has a switch (in this case, a double-pole switch built for 220V 45A), a plug, and the PID.
Initially, the PID is setup in Centigrade. You can change it by holding down ‘set’ for a few seconds and then pressing it until you see a C F in the upper screen and using <<AT and up or down to change it from C to F.
The output is 24 VDC. There is also an alarm that is basically a switch (normally opened, closed during an alarm condition). The set includes some slip brackets (that’s probably not the proper name) to mount it in a box.
The issue I ran into with this is that the thermocouple is a less-common thread size – I don’t have the correct size nut and my tap set doesn’t have the correct size, either. I did find the right size at the hardware store (a 6mm nut).
I also had to find the right locknut for the heating element. Apparently, this is standardized to a 1″ nut, and they run less than $4 at Grainger.
So the next post should include something about getting this running in sort of a basic semi-usable and somewhat unsafe configuration. I’m sure my 50 amp spa panel will be part of things, as well as the switch I used above, and the PID controller of course. However, the PID controller won’t be controlling anything until I get the solid state relay. That’s probably stuck in the harbor outside of Long Beach; fortunately it shipped a few weeks before the Chinese New Year, and you really only need a few days (if that) for it to leave China and not be affected by the holiday. So the delay is all on Long Beach.
In the meantime, I ordered a pair of SSRs to be shipped from Georgia. Which will probably arrive next Monday.