Converting my MES40 to PID control...
So, this forum says it's for the DIY stuff that might be of interest to everyone... So here we go...
Glossary:
MES = Masterbuilt Electric Smoker
PID = Proportional Integral Derivative Controller
SSR = Solid State Relay
As anyone who pays attention to the "Latest Purchase" thread will know, the control unit of my MES failed during my last smoke, and appears to be completely dead. As such, I decided to buy a PID Controller, Thermocouple, and a SSR to control the smoker's heat element and temperature of the chamber.
The advantage of the PID controller is that temperatures will be more accurate and dramatically more stable over time.
I have a MES40, 40" tall unit, with a 1200watt heating element that I bought from Lowes a couple years ago. This plays into the process here because I haven't found a relevant set of instructions that fits my version. That is one downfall of the MES line, they have about 47 million variations that are all different in the process for modding them.
This one, as it turns out, is the simplest to modify for PID control... :D
A little background:
To control the MES with a PID, you must change the wiring of the MES to be a dumb heater. This means heating when power is present, and off when power is removed. Depending on the model you have, this can be very simple or more involved with cutting the heating element wires and connecting them straight to the incoming AC wires.
Once this is accomplished the power to the heating element is controlled by the SSR, which is driven by the SSR output on the PID controller.
Note: If you want to follow this, you must be aware and purchase a PID that supports SSR's. Otherwise you will have to use a standard relay. The downside to this is that they have a finite cycle life, and if it fails closed, you risk burning the smokehouse to the ground (more on this later, as you'll see).
So, finally, onto the process of converting my smoker to PID Control...
I started by opening all of the covers on the back and bottom of my smoker. This way I could start digging through the wiring with my meter and figure out what needed connected where. Based on previous reading on the 'net, I expected to have to cut some wires, add connectors, and then put it all back together.
My plans of following other modification processes went out the window as soon as I had the covers open and it looked nothing I expected...
https://farm8.staticflickr.com/7810/...bacae31c_c.jpg20190328_105721 by ARNEWB, on Flickr
https://farm8.staticflickr.com/7877/...95b7f85b_c.jpg20190328_105728 by ARNEWB, on Flickr
I opened the back first, and that was where I found the MES over temp safety (in the oval opening on the left of the picture), and the connections for the heating element in the square opening on the right of the picture.
Since this didn't look like what I was expecting from other write ups, I laid it over and started opening the other covers. On the bottom, I found the middle compartment was nothing but the power cord coming in, and the other compartment is the confuser (sorry, YT reference).
Note 2: One of the things that I wanted to do if possible, was retain the factory over temp protection. Basically, even if the PID fails or the SSR fails closed, the heater will get shut off once it gets too hot.
So, as I was starting to track wires (ohms on the meter) I realized that the oval opening on the back was the temp shut off, not the temp sensor for the controller. This was good news, because I was wondering where the extra set of braided red wires was (set on the heating element, set on the temp shut off). Turns out, they are in series... Problem solved.
Now I started looking at how best to bypass the confuser and tie the element straight to the incoming AC cord.
Single easiest conversion??? Yep!
The incoming AC connection and the connection from the confuser to the element/shutoff circuit actually use the same plug set.
Also awesome, is that the connectors just so happen to be correctly setup, so that they plug together!!! [Shock]
https://farm8.staticflickr.com/7922/...70d56ac7_c.jpg20190328_111907 by ARNEWB, on Flickr
So, here we have the now defunct control box that I don't want or need...
https://farm8.staticflickr.com/7821/...7f6d79a8_c.jpg20190328_111854 by ARNEWB, on Flickr
From the bottom:
The two plugs with the colored wires are the control lines from the control panel at the top of the unit.
The plug with the two white braided lines are the temp sensor for the control unit.
The plug with black and white is the AC into the controller
The plug with the two braided red wires is out to the heating element circuit.
Next up, I mounted the new thermocouple, so that it was stubbed into the chamber, and then modified the back plate to fit. A little silicon and it is water proof again!
https://farm8.staticflickr.com/7875/...48001ab8_c.jpg20190328_114023 by ARNEWB, on Flickr
https://farm8.staticflickr.com/7854/...3a078678_c.jpg20190328_120603 by ARNEWB, on Flickr
On the inside, the temp probe sticks farther in, which will give a more accurate reading. I kept the thermocouple low, to keep the feedback loop pretty tight (the closer the element is to the probe, the less overshoot there is (to a point... lol, always some sorta gotcha)).
It is right next to the temp shutoff sensor, and you can see the old temp sensor that sticks out about .75" in the middle...
https://farm8.staticflickr.com/7844/...81479289_c.jpg20190328_114032 by ARNEWB, on Flickr
With the rack back in, the rack above is where I usually smoke things, so it will keep temp as close as possible where the meat is sitting.
https://farm8.staticflickr.com/7836/...ac8b3b6d_c.jpg20190328_114059 by ARNEWB, on Flickr
So, with the PID temp wired together, I did a test run and it works flawlessly.
In my next post, probably tomorrow, I will detail out the wiring of the PID, SSR, Thermocouple, and show the box that I am putting it all into for weather proof purposes.
Hope this helps someone!
