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Power-User

Join Date: May 2008
Location: Aggieland, Texas
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How can I build a temperature controller

05/14/2008 7:54 AM

I would like to build a temperature controller. I would like the display to be 2" leds. I would like the range to be from 100°F to 350°F. It would activate a relay to turn the power source on and off. For instance, I would like the temperature to turn off at 250° and turn back on at 248°. I would like the large leds in order to read the temperature at a distance. This would be used for a BBQ smoker. I need a wiring diagram, list of materials and source of materials.

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Guru

Join Date: Dec 2005
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#1

Re: How can I build a temperature controller

05/14/2008 11:54 PM

Buy a thermostat rated to 350F. Use the output to cycle a contacter on your power source.

Buy a 4" dial thermometer and thread it into your cooker.

Check Grainger, McMaster Carr, or Omega for parts.

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Power-User

Join Date: May 2008
Location: Aggieland, Texas
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#2
In reply to #1

Re: How can I build a temperature controller

05/15/2008 4:43 AM

I've already purchased a controller and hooked it up to a relay. It keeps the smoker at a uniform temperature. What I want to do is build the controller from scratch.

Thanks for you reply.

PAPADOC

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#3
In reply to #2

Re: How can I build a temperature controller

05/15/2008 7:47 AM

"Controller"? A temperature-operated switch (a "thermostat") fits the requirements.

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Guru
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#4

Re: How can I build a temperature controller

05/15/2008 8:30 AM

Source: appliance repair shop

List of materials: Temp controller circuit for oven w/ digital display

Diagram: Supplied with parts

Are you wanting to start production for sale or is this just a hobby? You could take your new controller apart and reverse engineer it to see how it works. Then redesign it to your liking. I would never suggest copying it for resale. My oven has a digital display. I would imagine you could substitute whatever size screen you wish so long as there are not any power requirement issues. You might try surplus store sites for quantities of new cheap controllers. I use www.surpluscenter.com for some of my needs. I am not sure if they would have controllers there or not as the inventory changes based on their acquisitions. I list the site as an example only.

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Power-User

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#5
In reply to #4

Re: How can I build a temperature controller

05/15/2008 9:19 AM

I want to build mostly as a hobby, but if my smoker gets good enough, I might sell some smokers with the controller. I've used surpluscenter and they are good. However, the controllers on the market have many functions. I want to build one that is a lot simpler. I just want to have it turn the power source on and off at specified tempatures. I need plans similar to those for the digital thermometer at: http://www.instructables.com/id/Multifunction-Digital-Thermometer/?commentflag=1210334580629#CGF4BHSFG0GJ2IX

A normal metal thermostat isn't accurate enough.

Thanks for you interest,

PAPADOC

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Guru

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#6
In reply to #5

Re: How can I build a temperature controller

05/16/2008 12:39 AM

Have fun with your "hobby"! Sorry my "simplistic" response wasn't what you needed or wanted.

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#7
In reply to #5

Re: How can I build a temperature controller

05/16/2008 7:46 AM

Our McEnglevan dual chamber heat treat furnace uses the Honeywell UDC 2300 mini pro. The tempering chamber typically is used at a temp range of 400 to 800 deg F. It has a type "K" t-couple and is able to hold +/- 2 or 3 degrees. You are correct, there are many features and functions and these are not cheap to replace. The programming sheet that came with them is 4 pages of parameters to set. Building one is beyond my scope. I am curious as to how precise the temp needs to be controlled for a BBQ smoker? Kitchen ovens are not nearly as precise as a heat treat furnace yet you can readily prepare meals everyday very reliably. I find it hard to imagine that with the typical over run / under run temp of the common oven you would not have a successful cooker. I have seen small smokers for sale through Bass Pro. I am not sure if they have a controller or not. You might check those out and contact the maker of those units for parts.

I used a wood stove for heat years ago. The controller on it was just a hinged damper with a spring attached to it. The damper controlled the incoming air to the firebox. You set the opening of the damper by simply pushing it closed or pulling it open and the spring would expand and contract with the temp change. As the stove cooled down it would open the damper. As the stove heated it would close the damper. Thus maintaining the room temp. The big safety feature was that if the fire tried to get out of control it would shut down the air flow completely. Yes that meant a lot of hot smoke and gases in the flue but it kept the fire box from over heating.

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Power-User

Join Date: May 2008
Location: Aggieland, Texas
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#9
In reply to #7

Re: How can I build a temperature controller

05/16/2008 9:46 AM

Thanks for your reply. My smoker is designed to make smoke as well as cook. A pan of hickory chunks is set on the burner to generate smoke. The large heating element like a 2500 watt or larger that electric ovens have will go off so long that I'm not able to get any smoke from my chunks. I use a 1000 watt heating element in a gutted electric oven. The 1000 watt element stays on long enough to get plenty of smoke. The hickory chunks are cheaper than the shavings and last longer and are more readily available. What I have works like I want. I place my brisket in there, put a pan of hickory chunks on the heating element, set the temperature to 250°F, after 4 hours put in some more hickory chunks, (I plan to try a bigger pan of chunks) then go to bed. Get up after it cooks (one hour per pound of brisket), let it cool a little, then cut it up. It is really delicious and almost foolproof to cook. I started out with the idea of a "drunk proof" bbq pit. But I realized that was impossible, so, now I'm trying to build a "Nearly Drunk Proof" bbq pit. I plan to make a wood fired one with automatic damper controls. That's why I'd like to be able to build my own temperature controller.

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#11
In reply to #9

Re: How can I build a temperature controller

05/16/2008 10:41 AM

On the cooking show "Good Eats" (Alton Brown) I saw a smoker made using a hot plate to smoke the wood chips. He was collecting the smoke in a water tray to make liquid smoke. Could you do something like that inside your oven?

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Power-User

Join Date: May 2008
Location: Aggieland, Texas
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#12
In reply to #11

Re: How can I build a temperature controller

05/16/2008 10:54 AM

I don't know. I use a pan of water to keep the meat moist and catch the drippings. I've got the process down pretty good. What I need is a low cost simple temperature controller. I'd like to build one myself with large leds so I can read the temperature at a distance.

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Guru
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#13
In reply to #12

Re: How can I build a temperature controller

05/16/2008 12:59 PM

I understand you wish to build one yourself. As this is summer break our electronics instructors are gone till fall. If someone drops by I will ask them for suggestions and pass that along. This is of interest to me also as I have been working on a grill/smoker as well. I am wanting to keep mine portable for family and church gatherings. I would love a big trailer mounted set up, but that would be over kill for most of my needs.

Till then, good luck

The Mechanic

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Power-User

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#14
In reply to #13

Re: How can I build a temperature controller

05/17/2008 4:48 AM

What you need is a gas operated smoker. I've built a thermostaticly controlled deep fat fryer utilizing the same controller that I purchased. It works excellent. However, to make a gas smoker will take more design. A smoker must be able to cook for hours without much attention and therefore, requires more safety. My deep fat fryer must be attended to continously due to the nature of the cooking. If the wind blows the flame goes out, you're right there to fix it. I want to build a gas smoker, but the NDP wood fired smoker project is ahead of it. The same temperature controller can be used for all my applications. However, it would be better to have a separate controller for each.

Later,

PAPADOC

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#15
In reply to #14

Re: How can I build a temperature controller

05/19/2008 7:23 AM

Since you are using gas, have you considered using a thermocouple in your controller design? I don't suppose you have looked at gas ovens for a controller? They already incorporate the safety features you are looking for. I am going to be using a military surplus storage container for a gas turbine engine as my cooker. It has thick walls which should help retain most of the heat. I do not plan on insulating it to make it more efficient. The cooking time will be short (dogs and burgers mostly) so insulation would not be a big issue. The cooking surface will be about twice that of a common gas grill. Its large barrel shape will also lend it to rotisserie cooking as well. Since it is round, I would like to make it look like a pig by welding on a nose, ears, and a tail. I plan on replacing the pressure gage with a thermometer. I will be using gas burners in it. Although, I have thought about adding a firebox for smoking.

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Power-User

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#16
In reply to #15

Re: How can I build a temperature controller

05/19/2008 7:41 AM

No. I'm using electricity. I use a 1000watt element. I have already made a gas fired deep fat fryer using my temperature controller and a solenoid valve. A gas oven might work but their thermostats aren't as sensitive as I prefer. Put a thermometer in your oven and check it out.

I really need to build my own temperature controller from scratch. That's what I need.

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#17
In reply to #16

Re: How can I build a temperature controller

05/19/2008 7:57 AM

Sorry, I reread all of the posts after sending the last one and caught my mistake. As I said before, I understand you wish to make one from scratch. I am just trying to offer help. I tend to keep all of my options open during a project. I keeps me from painting myself in a corner by limiting the possibilities. Nothing wrong with what you are trying to do.

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Power-User

Join Date: May 2008
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#18
In reply to #17

Re: How can I build a temperature controller

05/19/2008 8:17 AM

Thanks.

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#8

Re: How can I build a temperature controller

05/16/2008 7:55 AM

I just checked out the bass pro site. There are a couple of electric smokers. Here is the link to the page.

http://www.basspro.com/webapp/wcs/stores/servlet/SearchResults?searchOption=products&hvarSearchString=smoker&storeId=10151&catalogId=10001&langId=-1&CMID=TOP_SEARCH_GO

Good luck.

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Power-User

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#10
In reply to #8

Re: How can I build a temperature controller

05/16/2008 9:58 AM

See previous comment.

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Participant

Join Date: Apr 2011
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#19

Re: How can I build a temperature controller

04/29/2011 2:17 AM

Temperature Controllers - To accurately control process temperature without extensive operator involvement, a temperature control system relies upon a controller, which accepts a temperature sensor such as a thermocouple or RTD as input. It compares the actual temperature to the desired control temperature, or setpoint, and provides an output to a control element.

For more information about Temperature Controllers.... http://us.azbil.com

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Users who posted comments:

azbil123 (1); PAPADOC (8); PWSlack (1); Ried (2); The Mechanic (7)

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