Automatic Temperature Controller Build

[flykilbosa]

I recently upgraded from a $59 Brinkman smoker I got at Home Depot that I modified to building a UDS. After I built my UDS I smoked a few racks of ribs and a couple whole chickens, which both don’t take too long. I had concerns about the UDS holding/maintain temp for long periods of time because the experience I had with my $59 modified Brinkman was bad. The Brinkman would need coal or need me to mess with it every 3 hours or which made long smokes a pain in the butt. Little did I know the UDS, by itself, was far superior to the Brinkman with regards to temperature control and duration! Anyway, being nervous about it, I knew the UDS had the capacity to load about 30 hours of coal in it, so I wasn’t worried about having to add more, I was only worried about having to mess with the intakes to maintain temperature…anyone with a UDS knows I had/have nothing to get worried about. But, me being me, I’m always looking to tinker and find projects so I looked into building a temperature controller. Why would I spend $150-$300 on a controller when I could enjoy building one for way cheaper!!

I’ve looked into PID’s for my home brewing setup, but not knowing much about them and SSR’s and high voltage near 10 gallons of liquid I’ve been hesitant. Well with smoking, I realized I just needed to get away with running a simple 12 volt computer fan so I decided on building a DC temperature controller. I chatted with some electronic savvy guys I work with and instead of trying to learn every little aspect of how these things fully work, I picked up on the important stuff and declared the rest PFM (pure flipping magic). One of my coworkers explained and drew up a quick picture of how the PID will be wired to the SSR and where the fan, thermocouple and power come into play. Looking at the instructions for the PID that I chose, I noticed there was a wiring diagram that looked almost identical to my coworkers drawing…



My next question was, should I power this from a sealed 12 volt battery or what? How long would the battery last when fully charged, how often will the fan turn on…too many variables and a battery seemed too lame, I need to be able to plug it in to the wall so I know it will be powered for long smokes. I had a broken Wi-Fi router I wasn’t using and noticed the power adapter (AC in DC out) was going to be my solution. It pumps out 12 VDC and 1.5 amps.



The only 2 things I added to the wiring diagram in the picture above was 2 switches. 1 switch to turn the whole controller on or off when it’s plugged in and the other switch to physically (not through the PID) turn the fan on and off (I read somewhere someone did this so if you open the smoker the fan won’t go crazy running due to any temp loss). I picked up to switches at radio shack and wired everything in a project box I bought from Radio Shack.





I used size N coaxial plugs from Radio Shack for the fan and power connections and a K-Type thermocouple plug from Auber Instruments for the thermocouple.

Here’s the PID I bought… http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=83
Here’s the SSR I bought… http://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=128
Here’s the thermocouple I bought… http://www.auberins.com/index.php?main_page=product_info&cPath=20_3&products_id=173

Next was to find a fan and figure out how to “engineer” something so the fan can hook up nicely to one of the ball valves or nipple on the UDS. I found a fan that looked sufficient (I was looking for a fan that can pump out greater than 10 CFM…I read that somewhere) and pulled 0.9 amps so it went well with my 1.5 amp power adapter.

Here’s the DC blower fan I bought…. http://www.jameco.com/1/1/46752-ab0912mb-z01-12vdc-29-8-cfm-ball-blower-10-inch-leads-94-x-94-x-33-mm.html

While perusing pictures on Google, I found a picture where someone used a conduit box to attach the fan to the UDS with. Brilliant!! If I ever meet that person I will buy him/her a beer! I plugged the top hole of the conduit box, cut a hole in the box so the fan fit tightly and put some gasket material around the fan so it was “air tight.”



I calibrated the thermocouple/PID combo in ice water per the PID calibration instructions, put in ballpark P,I & D settings that people have had success with on charcoal smokers and let it rip yesterday. I was awesome!!!



I do want to tweak a setting on the PID that allows more time between cycling the fan on and off. I noticed from the time the fan cycles on and off, more time is needed to “realize” a change in temperature in the UDS...I'll have to figure out what setting controls that?

Anyway, this was kind of a quick recap on the build, let me know if you have any questions, remember I assume a lot of the PID function is PFM!!!

 

[Sammy_Shuford]

if i was at home, i would post a picture. Copper plate sized for fan discharge. Drill a 3/4 hole, and sweat plate to pipe fitting.

Been running that way for several years.