Author Topic: Question Regarding PID Controller  (Read 122 times)

Online Elfremi

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Question Regarding PID Controller
« on: September 11, 2019, 05:54:12 pm »
So I've been modding my Bradley BTDS76P 4 Rack Digital Smoker. We moved to a new home nearly two years ago and the smoker wasn't performing well. It had a hard time coming to temp and recovering from opening the smoker door. It always seemed to have difficulty before coming to temp, especially during the colder months, but ever since the move, it wasn't able to reach 225F. I could reach around 210F to 215F. So I finally decided to upgrade my heating element. I installed a 900W element and upgraded the wiring to handle the extra current. I purchased a PID controller on Amazon and also purchased a circulation fan from Auber Instruments.

After installing the element, I noticed the likely culprit regarding my smoker's difficulty reaching temp. There was a huge 2-inch by 2-inch gap in the top left-hand corner of the door seal. My smoker was in storage for around 8 months when we were between homes and I guess that section of the gasket got compressed, creating a permanent gap. I had a corned brisket to smoke in a few days, so I just put a bead of silicone in that corner to fill in the gap. It's not perfect, but it's certainly better than it was. I have a new door seal on order and I'll install it once it gets here.

While I modded my smoker thinking the only issue was the heating element, I certainly don't regret my decision to do so. Even with the less-than-ideal seal situation, the smoker is still coming to temp much faster and recovers much better than before. I can only imagine how the smoker will perform with a new door seal. Anyway,  I built my PID controller box and it works well enough. Here are some photos:









Here's a link to a short video of the PID controller firing the relay (not sure if the video will work, but worth a shot): https://imgur.com/MO2C1Gl

Anyway, here's my issue. I have two LEDs on the front of my enclosure box. There's a red LED connected to my PID that indicates if the internal temp of the smoker is beyond an acceptable range. The second LED (initially a white LED, but currently a green LED) lets me know when the PID is sending current to and switching on the relay. Here's where I'm having an issue with my setup. I never noticed it before, but even when no dc signal is sent to the relay, my green LED is still being dimly illuminated. Now, it might just be that when I was testing my latest setup (I added k-type thermocouple jacks and wanted to make sure they worked) I didn't have some kind of load plugged into the receptacle, so there might be some minimal floating current coming from the relay and dimly lighting the LED. It only needs 20mA after all. Here's a diagram of my current setup:



I'm considering changing my setup to have different LED being powered through the PID's signal to the relay instead of through the relay itself. Here's a diagram of my potential new setup, the only change being the green LED:



Just wondering what you guys (those electronically inclined) think would be the best solution.

Cheers!
Enjoy your next cook!

Online Elfremi

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Re: Question Regarding PID Controller
« Reply #1 on: September 12, 2019, 05:28:32 pm »
After looking more at the forum posts, it seems the mods are more in the accessories section.

Anyway, I switched the AC 110V LED connected on the relay output side with a DC 12V LED on the relay input side. I still get to see when the relay is being switched on, but no longer have that dim glow in the LED. Upon further searching online, it appears there's a small amount of voltage "leak" associated with the solid-state relay I have (it came with the PID), enough to dimly illuminate the LED in my previous setup.
Enjoy your next cook!

Offline Habanero Smoker

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Re: Question Regarding PID Controller
« Reply #2 on: September 13, 2019, 02:13:43 am »
I don't have any advice, but want to say your PID controller is well thought out.


     I
         don't
                   inhale.
  ::)

Online Elfremi

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Re: Question Regarding PID Controller
« Reply #3 on: September 13, 2019, 03:58:24 pm »
Thanks Habanero! I've only used my setup once, but giving it another whirl this Sunday with some pork belly strips from Costco.
Enjoy your next cook!