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View Full Version : Heat treat oven controle.



Bob Quale
09-21-2002, 04:20 PM
I have a little, electric, heat treat oven I purchased through Brownells. It works great but you have to keep fiddling with the power controle to maintain proper heat. Any one know of a home made temp controler? or mabe a generic less expensive one to purchase?

Thamks Bob

Thrud
09-21-2002, 06:22 PM
Bob

Thermal temperture indicating crayons or paint may be your cheapest route. A good thermocouple controller is not cheap. This is why the ovens with the good computer controls cost more - they are worth it.

alsinaj
09-21-2002, 07:18 PM
I have just built a heat treat oven proportional control that uses a thermocouple as the sensing element. Have not tried it out yet. Will be glad to share plans and PCB layout. Send me email. JCA

alumtuna
09-21-2002, 08:52 PM
hello bob

alumtuna
09-21-2002, 08:59 PM
Hello Bob,

You check out www.omega.com (http://www.omega.com) for temperature controllers for approx $150 for what you need. To add you need a thermal couple and relay(s) to control the electrical power or solenoid if gas powered. Also get a thermistor (-sp) for safety runaway overtemp cutoff control

Alumtuna

SGW
09-21-2002, 09:11 PM
Is this the Neycraft oven? I'd think it ought to be able to maintain temperature reasonably well; have you contacted Neycraft (or whoever the manufacturer is) to see if the behavior you're experiencing is "normal"?

Bob Quale
09-21-2002, 09:43 PM
SGW
Yes it is a neycraft. It heats up well but you have to keep an eye on it. If it had a controller, I beleave I could set the temp and let it soak. Perhaps I'm doing something wrong?

alumtuna
09-21-2002, 10:01 PM
try also automationdirect.com another control supplier (inexpensive). Not affiliated w/ any of these.

Good luck

Bob Quale
09-21-2002, 11:06 PM
I found some controlers! Do you put the wires from the thermocouple into the controller, and then the relays turn the power on and off to the heating element? Easy as that? I must be missing something?

Please confirm!

Bob

Weston Bye
09-22-2002, 09:24 AM
Yep, it's almost that easy. Make sure the thermocouple is compatible (type J, K, etc), and connected in the right polarity. Also, the controller relay must be capable of switching the oven current. If not, use the controller relay to drive a larger relay or a solid state relay sized for the job.

Wes

OB
09-24-2002, 03:30 PM
Several years ago, I converted my Neycraft manual control furnace with a Fuji temp controller:
See http://www.process-controls.com/cyronix/Fuji_PXV3_Fuzzy_Logic_Controller.html . It was very simple. Mount controller where meter is now. Connect existing thermocouple to controller. Add a solid state relay(use front panel for heat sink) to switch the heater power. Add a pilot light and main power switch where the original knob control is located. Wire it up and turn it on. Fuji controller will tune itself and your are in business. Mine holds temp setpoint within 1 degree all day long. You can get different options in the controller for ramp and soak routines, alarms, etc. if you need them.

docsteve66
09-25-2002, 10:09 PM
I've run "temperature surveys" and ovens big nuff for a man to walk around in. The "local charts" showed temp spikes, despite the controller being good. Problem was lack of load in the oven (also in one case, improper placement of sensor element.

On a smaller furnace, I THINK I would try the control from an electric stove element. Let it warm slower and avoid over shoots or build (buy, install?) a external control as suggested above. Ifyou are short of money and long on time, there are many circuits that disconnect on voltage rise. The thermocouple is a good reliable source of voltage to be sensed.

Be sure your sensor in the present oven is not close to the wall. nearer the cneter of the work space is best. The walls are slow to heat, keeping the sensor cool also.

alumtuna
09-26-2002, 04:08 AM
Bob Quale,

Also use thermalcouple wire for you could get an error in reading.

I agree w/ DocSteve66 w/ sensor placement. Most critical.

Some controllers have logic so that temperature does not exceeds a specific amount. Do not trust this for this is NOT a safety feature (only process control). If you have a runaway controller wicth happens often it could burn the house down :-(
Use a Thermostats that could shut off a runaway thermal condition. Sorry for the last post it was misleading (its not thermistor). Check out the web site for a general impression.

http://www.thermodisc.com/product.html

Again not affiliated.

Please post again

Bob Quale
09-27-2002, 04:53 PM
Well, I ordered a controller from Automationdirect. They were extreemly helpfull and thier prices are on there web site so no chasing phone calles for quotes. It should be here Tue or Wed. Thanks to all.


Bob

Bob Quale
09-28-2002, 09:32 AM
WEll

I also ordered the controler from fuji. They both looked real good. I'm going to see which one fits better and return the other. The Fuji is less expensive.