Design for ColdFusion Temp Controller with Relay

[KosherSmokin]

Hi everybody,
Here's my design for the ColdFusion temp controller with a high-current relay.
Because I'm not an engineer, I leaned towards a conservative design.
For the relay I used a gourmet, overpriced, 25A Crouzet, complete with touch-safe exterior and on-indicator LED!
I used this relay for two reasons:
    1. So that there would be NO excuse for it to break because of my relay
    2. So there would be minimal heat produced, especially because of the possibly rapid (10X/Sec) switching rate of the ColdFusion.
I posted to the Crouzet forum and they said it was completely within their spec. and I could rely on 10 million switching operations before it breaks.
Here's where I found the relay online (Part # 84137011):
http://www.onlinecomponents.com/search3z.cfm?Unique_ID=30258311

I wrote up the design first as a schematic, then as a wiring diagram, to make sure I would never have more than two wires to a post (they wouldn't fit!).
Schematic:

Wiring Diagram:

Finished Product (With the cover off):


The hardest part of the job was all the mounting and connections.
The other goal of my design was to make the connections as modular as possible, so I wouldn't have to worry about dragging a heavy cable along with me when I move the box.
I used female quick-disconnects which seemed to fit the thermocouple blades just fine, and a computer-style power jack.
Connectors (yes my office is a mess):

If I can't find a thicker 16-gauge computer-style cable (I only have 18-gauge), I'll probably switch it out for a normal male plug like the female on the right.

Please let me know what you think or if have any questions/problems.
As for controlling the Bradley, before coming up with this design I had another idea.
Once the Bradley is in heated and in maintain mode, could you not theoretically move the rheostat down somewhat?  This makes sense to me that it would both decrease the current demand of the element, and also minimize overshooting.
But there's probably a minimum level needed to maintain the temp too, so finding a point in the middle might be hard.
Just a thought.

Once again I am NOT an engineer, so I must say that
I MAKE NO WARRANTIES OF ANY KIND REGARDING THIS DESIGN (including burning your house down)! PLEASE USE IT AT YOUR OWN RISK! ^_^

Thanks again for this board, it's a real resource to all of us!
-Sam

[TomG]

Hi Sam, I used the same wiring config with my Coldfusion but added a terminal strip to manage the 2 wire per terminal problem, cut a 9', 3/14 air condiioner extentension cord in half for the I/O power,a Crydom 40A ssr, and used a Radio Shack plastic project enclosure as a box.

Pictures to follow-Tom-

[TomG]

Here is my Coldfusion box.  I thought the pid's LED would be ok for a power ON indicator and some day will probably add an internal fuse and an on/off switch.(Surrre)

[KosherSmokin]

Nice design, Tom.
I started with 14/3 cables too, but then I went to modular.
I still like the modular idea so I don't have to worry about pulling on cords, yours does look nice though.

1. Where did you find the grommets for the back (for the cords)?
2. Is the bottom metal or plastic?  Do you have a heatsink and how do you manage heat transfer to the outside?  My relay got a bit hot (~150) on a 10A load.  If I was playing it safe I might put a heatsink under it.
I used a radio shack box too but mounted it upside-down (the metal lid is my base) so I have the metal for heat conductance, but now I can't mount anything on the box because the box isn't where my project is, it's on the lid!
I'll move up to a bigger design once I figure out the heat.  I'm also contemplating a more expensive all-aluminum case.  How do you handle the heat problem?

Thanks!
Sam

[TomG]

Hi Sam, I get the grommets at Home Depot.  I couldn't find a heatsink so I cut slots in the side of the box and mounted the relay so it's metal base faced out and had direct access to air.  I've tested the unit for about 3 hours at 210* and the relay didn't get above 95* with a 65* ambient.  If heat becomes a problem inside the box I might consider some kind of insulation around the relay.

Cheers-Tom-

[Oldman]

Very nice guys.... this is one post to book mark for sure.


Olds

[lvigil]

It seems like these temp controllers work well.  Is anyone willing to make one up and sell it?  It sure has to be alot less expensive than the raptor guru.  I have no wiring skills.  I just want plug and play.

Watch Out!! Hot and Spicy (<:}

[JJC]

I'm with lvigil--anyone willing to make and sell these?

NSXBill--would the Guru folks be willing to consider making this simplified temp controller and selling it at a reasonable price?  If they could figure out a way to modularize the system, they could get people buying the basic unit initially and then eventually working their way up to the full-function wireless unit by selling additional modules (e.g., programming module, wireless remote monitor/control).

John
Newton MA

[JJC]

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by KosherSmokin</i>
<br />Hi everybody,
Here's my design for the ColdFusion temp controller with a high-current relay.
Because I'm not an engineer, I leaned towards a conservative design.
For the relay I used a gourmet, overpriced, 25A Crouzet, complete with touch-safe exterior and on-indicator LED!
I used this relay for two reasons:
    1. So that there would be NO excuse for it to break because of my relay
    2. So there would be minimal heat produced, especially because of the possibly rapid (10X/Sec) switching rate of the ColdFusion.
I posted to the Crouzet forum and they said it was completely within their spec. and I could rely on 10 million switching operations before it breaks.
Here's where I found the relay online (Part # 84137011):
http://www.onlinecomponents.com/search3z.cfm?Unique_ID=30258311

I wrote up the design first as a schematic, then as a wiring diagram, to make sure I would never have more than two wires to a post (they wouldn't fit!).

The hardest part of the job was all the mounting and connections.
The other goal of my design was to make the connections as modular as possible, so I wouldn't have to worry about dragging a heavy cable along with me when I move the box.
I used female quick-disconnects which seemed to fit the thermocouple blades just fine, and a computer-style power jack.
Connectors (yes my office is a mess):
If I can't find a thicker 16-gauge computer-style cable (I only have 18-gauge), I'll probably switch it out for a normal male plug like the female on the right.

Please let me know what you think or if have any questions/problems.
As for controlling the Bradley, before coming up with this design I had another idea.
Once the Bradley is in heated and in maintain mode, could you not theoretically move the rheostat down somewhat?  This makes sense to me that it would both decrease the current demand of the element, and also minimize overshooting.
But there's probably a minimum level needed to maintain the temp too, so finding a point in the middle might be hard.
Just a thought.

Once again I am NOT an engineer, so I must say that
I MAKE NO WARRANTIES OF ANY KIND REGARDING THIS DESIGN (including burning your house down)! PLEASE USE IT AT YOUR OWN RISK! ^_^

Thanks again for this board, it's a real resource to all of us!
-Sam

<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Kosher, as they say in Guiness-land . . . Brilliant!

John
Newton MA

[ritzdeliman]

Nice package... the boys at NASA must be proud. Would'nt mind one myself, so giver in the patent office and you got my order. ritz

[TomG]

Hi Guys, this is a reasonably easy project.  I think the main problem for a manufacturer would be product liability, on the other hand it mght be easy to market a ready to assemble parts kit which, with disclaimers might protect the seller.  I will be more than happy to post all of my component sources and pictures of step by step assembling and I'm sure with Koshers great schematics, building the controller would be a piece of cake.  Opps! I meant a piece of pulled pork.

Cheers-Tom-

[SMOKEHOUSE ROB]

Tom g, please post all of your component sources and pictures of step by step assembling. thanks

[rgardjr]

Here's what mine ended looking like:

It's modular plugs in-line between power and smoker.  Thermocouple is permanently installed in smoker and has a cable that plugs into jack on PID box and jack on back of smoker.  I had absolutely no luck with the included thermocouple from ColdFusionX so I had a couple made for me.  Bought most of the parts from DigiKey and the thermocouple jacks from Omega.  I idiot proofed the cables so that it can only be plugged into the smoker the correct way.  Can somebody post your PID settings for me.    I did an auto tune with mine and it maintains temperature within a 1-2 degree range, but I have it set for 215 and it only gets to 213.  Seemed kind of strange just wondering what everybody else is seeing.  The full thread on all my mods that I made is in the accessory forum:
http://www.bradleysmoker.com/forum/topic.asp?TOPIC_ID=2567
Rick

[TomG]

Hey Rick, now that is sweet!!! What is the wattage of your heating element and how did you install the fan assembly?  These are the defaults on my TCG-6131P:

Parameter   Meaning   Value Range   Comment   Default Value
(1) So   Output Target   0~999 deg C   Set target value   150
(2) SHP   Upper Limit Offset   -20~999 deg C   Above this value the red alarm indicator turns on. Alarm relay connects closed   10
(3) SC   Thermocouple correction   -20~20    To correct offset error of conductions.   0
(4) SOH   Target Value Upper Limit   0-999   Limits target value upper limit.   20
(4) P   Proportional band   1~span   Set heating-side proportional band.   20
(5) ]   Integration time   0, 1~3600 sec   To eliminates offset occurring control. 0=Function turned off.   130
(6) d   Derivative time   0, 1~3600 sec   To prevent ripples by predicting output change thereby improving control stability. 0= Function turned off   30
(7) t   Proportional Cycle(Heating side)   1~99 sec   Set control output cycle. Short cycle time make output become pulses.   20(2)
(8) Ar   Auto tunning   00: off01: on       00
(9) LoK   Lock Setting   00: Not lock01: Lock all but main control02: Lock all parameters   To allow or not allow parameter change.   00
 
If the above doesn't help I can email an original copy of the manual.

Nice work-Tom-

[rgardjr]

The element is 750 Watts.  Somebody else around here did it before and I copied their idea.  The fan is from Olds design the thread has been mostly dismantled, but it does have the links to the motor and blades that you need.  Basically build a bracket to hold it to the smoker and drill a hole through to the inside that the shaft will fit through.  I did reinforce the back of the smoker where the fan mounts so it would be more sturdy.