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Control Heat Gun via PWM
fg1972
Hi all,
I'm currently roasting in a behmor and about to put together a bread maker/heat gun combination for something different and possibly to be able to do larger batches.
I've assembled an Arduino TC4 and had a play with Artisan and RoastLogger software.
I am thinking about controlling the heat gun's output via PWM from the TC4.
Does anyone have any experience driving a heat gun via PWM signal?
Is it best to split the fan/element circuit and vary the element only?
 
allenb
Howdy fg and welcome to HRO. I see you reside in the land where the Corretto was born.

If by PWM you're referring to the on-off proportional duty cycle many of us use to control an SSR from OT1 pin then it will work fine for driving an SSR connected to the heating element of your heat gun. I wouldn't use the higher frequency pwm used for driving fans for this purpose. You can set the heater output (OT1) to a 1 second time base which provides a very smooth output from the heater without sagging during on/off pulses.

Yes, do separate the fan from the heating element but be aware that many heat gun designs use some of the heating coils as a dropping resistor to derive a lower voltage that then feeds a bridge rectifier for providing DC to the fan motor which can complicate the separation procedure.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
fg1972
Thank you Allen,
I'll have a bit of a play with the TC4's outputs by configuring it to drive an LED as a test.
As for separating the heat gun's element and fan, would I be correct to presume the fan should be configured to be on constantly and only the vary element's output?

Fiorello
 
allenb
Yes, the fan should remain on and vary the power to the heating element.
I'm assuming your heat gun has a dc fan motor as you would find in a blow dryer? If yes, then its important to measure the voltage going to the motor (before the rectifier) prior to pulling everything apart so you can run the fan at the same speed after separating them. Obviously you'll need a means of providing the lower ac voltage to the rectifier input.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
fg1972
Perfect,
Thanks again Allen.
 
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