PID CONTROLLER
From rob

It should be noted that while I authored this article, I'm not the originator. This project was only made possible through the efforts of many members from the Bradley Food Smoker Forms. To name a few that I know of Bubbagump, TomG, begolf25, Arcs_n_Sparks, car54, gary_CO and I'm sure many others.

To all of those who made this project possible I cannot thank you enough, and a special thanks goes to begolf25 for answering my questions and all of his help.


Do Note: I am not an electrician and claim no special knowledge about electricity. I don't know anything about wiring diagrams. I made the supplied wiring diagram based on information found on the Bradley Food Smoker Forums. I made a PID control box based on this diagram and it works perfectly. Auber Instruments suggests that a fuse be used with this PID. I've been told by others that because this box plugs into the smoke generator (which is fused), that a fuse is not needed.
  • Disclaimer: Should you decide to create a controller based upon this article and it burns down your house, causes a death, or any form of harm it is solely your responsibility. This article is for my personnal interest only. It is not meant to be used for commercial purposes; nor is this article a guide for building a PID controller for your food smoker. It is a step by step of how I built my unit. Again this article is only for my personnal interest.
    Proceed at your own risk!
I really found this to be an easy project, even having no knowledge of electricity. The hardest part for me was rounding up all the supplies.

I think that by looking at the supplied picture and reading the text, it should be clear how I proceeded through each step. If the instructions are not intuitive, please E-mail your suggestions on how to improve them to the Webmaster.

The total costs for the project should be about $100.

I have found Auber Instruments to be very good to work with. They processed and delivered my order right away and answered questions via email.


Supplies needed - Click To Enlarge All Images:

1 Auber Instruments PID (For SSR Output)1 25A SSR1 Thermocouple1 Terminal strip with at least 3 terminals
(Order online, or try Lowes, Radio Shack or local hardware store)



The next two image do not enlarge

I used a 6 terminal strip from RadioShack.(Radio shack #270-1807 7x5x3")
1 Project Box


4 -10" pieces of 16 AWG wire
1 power cord
(I purchased a 10 ft heavy duty power tool cord from Lowes) I wanted something that would be flexible in the winter time.

Wire connectors are optional. I just used the bare wires for all of my connections.

Hole grommets are optional. They help so that the power cords don't pull out.
They are rubber inserts for the drilled holes. I bought a pack of 6 1/4" for
$1 at the hardware store.

Tools needed:
  • Philips screwdriver
  • Wire stripper
  • Dremel or similar rotary tool
The Box:
  1. The box comes with a removable cover. Decide if the cover will be the top or bottom of the box. It doesn't matter.
  2. The PID comes with instructions for making the cutout for the PID.
    • Basically, I needed to cut a square in the face of the box big enough to slide the PID through. The PID comes with a bracket that slides onto the back of it to hold it securely into place. I did not slide this bracket on until all of my wires were hooked up. I found it hard (but not impossible) to get the bracket off once it's on. I made my cutout pretty tight so I didn't even use the bracket. This will allow me to take the PID out if I need to at a later date.
  3. Keeping step 1 in mind, I drilled 3 holes in the back of the box.
    • 2 holes need to be about the diameter of a power cord. 1 hole is for the thermocouple and just needs to be small enough to fit the connecting end of the TC through. I cut the connecting end of my TC off, to make a smaller hole. Besides, the connections that came on the TC didn't fit onto the PID. You can see in the pictures that I used 1/4" hole grommets for all 3 holes. These help so that the cords don't move in or out.
The Power Cord:
  1. First, I cut it in half.
  2. Next, I strip the protective covering (the outer part) very carefully so that you can slide about 7 inches of the outer part off, leaving the green, white, and black wire exposed. I did this to both cords (male and female).
  3. Then I strip 1/4 inch off the ends of the green, white, and black wires. I did this to both cords (male and female).
  4. At this point I slide the cut ends of the power cords through the 2 larger holes in the backof the box. Hole grommets are optional.
The Thermocouple:
  • Next, I slid the connecting end (2 wires) through the smaller hole in the back of the box.
The PID:
  • Next, I Slid the PID into the box (it slides in from the front) just far enough so I could connect the wires, not all the way. At the same time keeping in mind, which side is the top on the PID and what side is the top on the box.

Click To Enlarge Remaining Images

About the Supplied Diagram:
  • The image shows the actual PID, Terminal strip, and Solid State Relay.




The Following Steps Are My Connections: *
  1. Connected the thermocouple (TC) to the PID. On the PID, 4 is positive and 5 is negative. The positive on the Auber TC is red. The negative on the Auber TC is yellow. Tightened these two screws.
    • In the diagram, positive is red and negative is yellow.
  2. Connected the ground wire (green) from the power cord with the female end to "A" on the terminal strip. Tightened this screw.
    • This is drawn as a green line in the diagram.
  3. Connected the ground wire (green) from the power cord with the male end to "D" on the terminal strip. Tightened this screw.
    • This is drawn as a green line in the diagram.
  4. Connected the hot wire (black) from the female end of the power cord to "T1" on the solid state relay (SSR). Tightened this screw.
    • This is indicated as a black line in the diagram.
  5. Connected the neutral wire (white) from the female end of the power cord to "E" on the terminal strip. Tightened this screw.
    • This is drawn as a white line in the diagram.
  6. Connect the neutral wire (white) from the male end of the power cord to "B" on the terminal strip. I did not tighten this screw yet.
    • This is indicated as a white line in the diagram.
  7. Connected one of the pre-cut wires from "B" on the terminal strip to "10" on the PID. Tightened both screws.
    • The pre-cut wire is blue in the diagram.
  8. Connected the hot wire (black) from the male end of the power cord to "C" on the terminal strip. Don't tighten this screw.
    • This is indicated as a black line in the diagram.
  9. Connected one of the pre-cut wires from "C" on the terminal strip to "9" on the PID. Tightened both screws.
    • The pre-cut wire is blue in the diagram.
  10. Connected one of the pre-cut wires from "F" on the terminal strip to "L1" on the solid state relay (SSR). Tightened both screws.
    • The pre-cut wire is blue in the diagram.
  11. Connected one of the pre-cut wires from "7" on the PID to A1(+) on the SSR. Tightened both screws.
    • The pre-cut wire is blue in the diagram.
  12. Connected one of the pre-cut wires from "8" on the PID to A2(-) on the SSR. Tightened both screws.
    • The pre-cut wire is blue in the diagram.



Test 1:
  1. Being careful not to touch any exposed wires, terminals, ect., I plugged the power cord with the male end into a power outlet.
  2. At that point the LED on the PID should light up. Holding the end of the thermocouple in my hand I saw a temperature rise on the PID. If not, then the positive and negative connections for the TC are likely backwards.
  3. Next, I unplug the PID.
  4. Then I finish sliding the PID into the box. There is a supplied bracket to mount the PID to the face of the box. This is optional depending on how tight the PID fits into the cutout.
  5. My next step was to mount the SSR and terminal strip using screws or other creative method. I actually just laid everything in the box, using the wires as cushion and didn't mount anything. I don't know if this is a bad idea.



  6. I placed the cover on box using supplied 4 screws.


Test 2:
  1. I plugged power cord from PID control box with male end into smoke generator.
  2. Next I plugged the smoker into the power cord on the PID control box with the female end.
  3. Then I plugged the smoke generator into a power outlet.
  4. My next step was to drop the end of the TC into the top vent of the smoker and let it hang in the middle, not touching any metal.
  5. Slide the slider control for the heating element to the far right.
  • The user manual for the PID explains how to run auto tune (AT). In AT mode, the display will flash AT. Set the temperature on the PID to a temperature that I normally smoke at. The PID will overshoot and undershoot that temperature 3 times and then AT will stop flashing. The auto tune is done.
  • After running auto tune on my box, there was a 10 degree swing in both directions. I ended up manually setting P and D values back to default (listed in manual) and taking I all the way up to 2700. With these values, my PID control box maintains temperature +/- 1 deg f.

Optional Heatsink:

At first I didn't use a heatsink on the relay, but after consulting with other users I decided to put one on. I really didn't notice alot of heat coming from the SSR. I think that adding a heatsink may be a judgment call. They are cheap enough, and alot of people have one laying around from an old processor or video card. I added onejust to be on the safe side, and I didn't want to be done with the project. So, a heatsinkis like a realy cheap insurance policy that could jack the price up on the project another ten bucks or so.

I took a heatsink off of an old video card. When I pulled it off, part of the chip came with it. I didn't have any thermal epoxy, but I did have thermal compound. Doing a little research, I found out that you can make your own thermal epoxy rather easily. Overclockers. I went to the local hardware store and bought some JB Weld. It's rated for 600 deg f. I mixed 2 parts JB Weld with 1 part thermal compound to make my adhesive. The reason I needed a strong adhesive? I didn't want to use any funky brackets, etc. to mount this thing. I just wanted the heatsink to be glued on and stick nicely out the back of the box. I do think that it would have looked pretty nice if I didn't accidently let the rotary tool rest on the box. My plan of attack was simple: make a cutout just big enough so that the heatsink fits in really tight. That's the mount. It works. I can try to push it in or pull it out and it doesn't budge. So using my method:
  1. I carefuly make a cutout just big enough to squeeze the heatsink through the back of the box.
  2. I place heatsink through box just enough to make contact with the SSR.
  3. I applied thermal epoxy to SSR, and clamped for at least 6 hours.
    • Note: I did not use PID (long enough for the SSR to heat up) for the first least 24 hours. Thus insuring that the epoxy had time to dry.


Obviously, there are so many different sizes and styles of heatsinks. It would be difficult to write a tutorial that works for all of these. I'm sure that other users will chime in (and some allready have) on the Bradley Food Smoker Forms. and will give you ideas about mounting heatsinks.

The picture of TomG's box (looks the same as mine). This shows that he mounted terminal strip, ssr. It also shows the bracket piece that slips onto the PID to hold it in the box.




TomG adds a custom heatsink.


These are pictures of Car54's PID controller:






These are pictures of MRH's PID controller:






Bubbagump mounted his PID controller inside of the smoke generator.




Questions I had about PID placement in smoker box.
Discussion regarding using an inline fuse.
Credit for idea.

If anyone has questions about my project then post them to me at the Bradley Food Smoker Forms.

Good luck!
Rob

*-Diagram has been checked by others for accuracy