PID Control at Low Temps

Scotty-G · January 10, 2007, 01:30:05 PM

Built and have been testing my new PID.
Used the Auber PID, SSR & T/C.

Here's my set up:

Added to my project box a power switch that enables me to leave everything plugged together but I can
1) switch off power to the puck advancer and still enable main heating element in the BS
and/or
2) switch off power to the BS heating element and "cold smoke" while still monitoring the temp using the PID without having to unplug things

After a few glitches with my set up not matching exactly my wire schematic, etc. my box was assembled and reading temps properly.

Ran the Autotune at 190 deg and it took about 1 hr total. Temp control was quite good with no swinging

Went to make jerky and set the PID to 145 deg. Temp hit 145 quickly and then continued to climb. Wound up sliding the power controler on the BS from full up to about 1/3 on and was able to control to about 150 deg.

Has anyone else using a PID experienced the same problems/experiences with trying to control the BS at lower temps? ???

Mr Walleye · January 10, 2007, 01:46:20 PM

Hi Scotty, first off nice job, it looks great. I don't have a PID but I'm looking at building one. In the reading I've done I seem to remember a number of guys having problems with consistancy with the Auber TC. I believe most recommended the TC from Omega. Hopefully they will chime in here with some better advice.

I'm having trouble locating a project box because of where I live. Where did you get yours from?

Mike

Scotty-G · January 10, 2007, 02:08:04 PM

Hey Wally,
Here in the silicon valley we have a few electronics spare parts surplus stores/junk yards. I stopped into one near my work and they had a few of these. It was less expensive than the radio shack project box and looked kinda neat/different. I guess I would check to see if there are any companies in your area that purchase used electronics and then resell to general public. High chance they might have or can get them. Also, check the internet. Most people seem to be using the Radio Shack one.

When I was doing my research, I first came across bubba gumps custom PID (do a search and you will find it easily) where he put the PID and stuff into the Bradley Smoke Generator Box and it looks like he did a GREAT job on it.

The Auber T/C has been working fine, I have been running an Oregon Scientific Temp Probe next to the Auber T/C and the PID readout has matched the Oregon Scientific the whole time. My gut is telling me that the lower temp is just too difficult for the PID to maintain with such a powerful heating element in the BS but with a PID fast response time, not sure why the PID wouldn't be able to regulate power to maintain a lower temp.

nodak · January 10, 2007, 02:10:47 PM

I had the same problem at low temps until Things settled in. My problem was I shut the puck burner off and than had problem at low temp so I had to retune it. Was your puck burner on/hot when you ran auto tune. I had poor luck with my auber TC so I bought an Omega. But if you are running a plug for tc need to use same wire as TC.

As far as a box goes I got mine at radio shack, you could also use a small tool box.

Mr Walleye · January 10, 2007, 02:28:25 PM

Thanks for the tips guys. Scotty, I have the DBS so I will have to mount it in a separate box. In Canada we don't have a Radio Shack although we do have Circut City who bought out the Radio Shacks here. They don't sell them . Besides them there are no other electronic stores where I live. I will have to do some seaching I guess. I will follow this thread to see how others have made out at lower temps.

Mike

nodak · January 10, 2007, 03:00:37 PM

Instead of a Project box. Go to an Electrical dept in a Home Improvement store and look for a plastic gray junction box used For running wire inside PVC conduit pipe You can plug the holes with caps of on one of them put a wire holder-clamp for running out your plug-in cord. I hope you understand this as I'm having a hard time putting into words what to look for. I've used these for a similar project where I needed a heavier box than a project box.

Mr Walleye · January 10, 2007, 05:21:14 PM

Thanks Nodak, Thats an excellent idea. I will definitely check that idea out.

Mike

Arcs_n_Sparks · January 10, 2007, 05:41:22 PM

Scotty-G,

Remember, you are controlling only part of the thermal loop with the PID. You have heat input from both the puck burner as well as the heating element. Your loop control dynamic is complicated by that.

Arcs_n_Sparks

jnmsnow · May 19, 2007, 03:18:30 PM

Quote from: nodak on January 10, 2007, 02:10:47 PM
I had the same problem at low temps until Things settled in. My problem was I shut the puck burner off and than had problem at low temp so I had to retune it. Was your puck burner on/hot when you ran auto tune. I had poor luck with my auber TC so I bought an Omega. But if you are running a plug for tc need to use same wire as TC.

As far as a box goes I got mine at radio shack, you could also use a small tool box.

Which Omega did you purchase?

Thanks
Mike

Mr Walleye · May 19, 2007, 06:09:37 PM

This is the one I ordered from Omega

TJ96-CASS-316U-3-SB-SMPW-M

The 96 Stands for how long it is.

Here is a link to the PID I built.

http://forum.bradleysmoker.com/index.php?topic=4735.0

Mike

Patience · May 21, 2007, 07:10:13 AM

I have very good control at low temps using Auber PID and omega TC. I autotuned at 160 degrees (usual final cook temp for jerky/sausage) and starting at 120, it only overshoots 2 or 3 degrees initially, then holds within 2 degrees even when ramping up to the next setting. I don't know if autotuning at a higher temp will increase the overshoot at lower temps...

Also, I keep the puck burner on all the time, protect it from the wind, and preheat so all the inards are nice and warm before running the PID. I guess try autotuning at a lower temp, then see if you get overshoot at your higher settings, keeping everything else constant.