SmokinTex 1430 Smoker PID Temperature Controller Modification

Disclaimer...
I am not a licensed electrician nor a certified appliance repairman. If you decide to do this or something similar you will be working with 120VAC which needs proper respect. I follow 1 rule: Don't tell your wife. Proceed at your own risk.

Purpose:
I started using a Stoker to monitor my SmokinTex 1430 electric smoker. This is a very good smoker, just set it and forget it (well almost). As with most heating devices there is a temperature swing between on/off cycles as the device attempts to maintain a reasonable average temperature as close to the desired setting as possible. My smoker's temperature range was 30+ degrees(F) with as setting of 200 degrees. The geek in me said this could be improved. With a little research, I decided a PID temperature controller was the way to maintain a more stable oven temperature.

Justification:
Smoking with a more stable temperature should make for a more consistent smoke. This may cause less wear and tear on the heating element - you wouldn't alternate between full throttle and coasting to average the desired driving speed in your car. It's fun and interesting (you're reading this).

Original Smoker Set Up

Image Original Circuit Original

    Smoker Parts (Back insulation has been removed)
  • A - AC in
  • B - Thermostat
  • C - Heating Element connection
  • D - Thermocouple connection

A closer view of the heating element connection (C). I didn't have to make any connection changes here.
Heating Element Connection

The basic design is simple making it easy to modify.

Modified Smoker Set Up / Part 1 / Initial Modifications

Image Modified Circuit Modified
    Modified Smoker Parts (PID/SSR not connected)
  • A - AC Socket/Terminal Strip (See Notes)
  • B - AC to PID/SSR
  • C - DPDT Switch to Heating Element

Toggle (C) for switching between the SmokinTex thermostat and the PID controller.
Heating Element Switch

The first modification placed a DPDT switch between the heating element and the rest of the SmokinTex circuit.

Modified Smoker Set Up / Part 2 / Ready to Assemble (Almost)

Modified Back Modified Connections
    Additions to SmokinTex Back
  • A - Back of AC socket
    Front Plate Modifications
  • A - AC Feed to PID / SSR
  • B - Controlled AC from SSR to Heating Element
  • C - DPDT Switch to Heating Element Control
  • D - PID to Thermocouple

Modified Smoker Set Up / Part 3 / PID Assembly

PID Picture PID Diagram
    PID Assembly
  • A - AC Feed to PID / SSR
  • B - Controlled AC from SSR to Heating Element
  • C - DPDT Switch to Heating Element Control
  • D - PID to Thermocouple
  • E - Stock Temperature Controller
  • F - AC Hot (black)
  • G - AC Neutral (white)
  • H - PID Controller On/Off
  • I - Solid State Relay
  • J - PID Temperature Controller
    PID Assembly Diagram
  • See picture legend (left) for reference
  • Heater and Thermocouple are located in the smoker
  • H - On/Off Switch not shown in diagram

Modified Smoker Set Up / Final Assembly

Final 1

Mounted PID temperature controller.
I may have to add a small smoke stack on the vent hole. The heat isn't a problem, but the smoke tends to cover everything with a sticky glaze. May use a tin can with both ends cut out.

Final 2

Connections between smoker and the PID controller.

Final 3

The PID controller thermocouple was wired directly beneath the SomkinTex sensor so both readings will be close to the same. I originally had it above the SmokinTex sensor but the smoker shelf bumped it when in position.
Heater element is visible at the bottom.

 Final 4

Electrical socket that doubled as a terminal connector.
The heater element draws about half of the available wattage.

Test Results

SmokinTex Temperature Profile SmokinTex Temperature Profile

Stock Smoker Temperature Profile

    Conditions
  • Approxomatly 10lb pork butt (picnic) was smoked
  • The temperature setting was 225F for both smokes
  • 2 temperature probes were used (Stoker): Red line, back of smoker, Green line, front
  • PID auto-tune was run when the smoker came up to temperature
  • 5 1/2 to 9 1/2 hour range was chosen for a stable interval on both smokes
  • Outside temperature was around 55-65F

Modified PID Smoker Temperature Profile

    Observations, Conclusions, Speculation
  • The overall temperature swings dropped from about 30F to 10F
  • The average reported temperature was lower than the PID set point
  • When testing with an empty smoker, the PID had a hard time zeroing in on the set temperature, running 20F or more too hot. From my observations, it appeared this may have been caused by the slow cool down when the heater element was shut off. This may have been caused by:
    1. The heating element doesn't stop radiating immediately when shut off.
    2. The smoker is well insulated.
    It worked much better during an actual smoke with meat in the oven.
  • The location for the PID temperature sensor (next to stock sensor) was not a good place for it. It didn't give a very good representation of the actual smoker oven temperature.
    2 possible fixes:
    Adjust the PID set temperature to compensate.
    Move the PID sensor to get a more representative temperature reading.
  • The PID controller I installed is actually programmable. Should be interesting to experiment with multiple temperature steps. For example: Having the temperature slowly rise from 210F to 250F over a 12 hour smoke.

    Tips
  • Don't try to go small with the PID enclosure, makes construction much easier
  • Electricians will note that I could a used a SPDT switch to enable the PID (using a common AC neutral). I used a DPDT switch so that which ever way the switch was set the 'other' side was completely out of the circuit.
  • Being able to switch between the stock temperature control and the PID control turned out to be very handy.
  • When modifying the temperature control there is the possibility of running the smoker at a temperature much higher than it was designed for. I am trying to figure out if this PID controller can be set to shut down at a specified temperature.

Construction Notes

Using an AC Outlet as a Terminal Strip

For an outlet to also serve as a terminal strip, you have to get an outlet with the correct type of connector. Do not get one with a simple screw type connector (the cheapest). Instead, find one that clamps down on the stripped end of the wires.

The outlet below has 4 neutral (white) and 4 hot (black) connections. One (and only one) connection on each side is the AC input. The other 3 connections feed the other AC devices. Observe the wattage limitations of the AC source.

Electrical Outlet