Temperature controller with resistive heating element. Help with circuit.

Using Arduino Project Guidance
#1

Hello, I am hoping to build a temperature feedback controller using the Arduino, an op amp of some sort, and a resistive heating element. There is a thermistor built into the heating element that will allow me to measure the temperature. The feedback program is not my problem, it is how to build this circuit and with which op amp?

I need to control the heating element current between 0 and 2.5 Amps, which has a total resistance of about 10 Ohms (I am using two in parallel). Everything else can be changed in any way so as long as the circuit works. I will be using the Arduino’s PWM and running it through a low-pass filter to the analog input (unless there is a better way that I am not aware of?).

The heating element is here:

http://www.thorlabs.com/thorProduct.cfm?partNumber=HT10K

Which op amp will work for this system?

Do you have any other suggestions that might make the system work better?
Should I use a buffer?

Thanks a lot

#2

To push 2.5 Amps through 10 ohms you will need a 25V power supply.

To control the heat the easiest way would be a logic-level MOSFET controlled by a PWM pin.

I don't know what you want the op-amp to do.

#3

Thanks for the reply John.

I have a variable power supply that operates between 0 and 30V. Is there a specific MOSFET that you would recommend? Thanks again.

#4

KDanielH:
Thanks for the reply John.

I have a variable power supply that operates between 0 and 30V. Is there a specific MOSFET that you would recommend? Thanks again.

https://www.sparkfun.com/products/10213?

https://www.sparkfun.com/products/10256?

#5

The system that I am controlling is sensitive to magnetic fields and I therefore cannot have a current controlling the heating element that switches on and off rapidly. So, I don't think the MOSFET will work for what I'm doing, since it does just that. Does anyone have any suggestions for controlling an analog DC current, so that it won't be changing rapidly in time?

Thanks for the help, guys.

#6

KDanielH:
The system that I am controlling is sensitive to magnetic fields and I therefore cannot have a current controlling the heating element that switches on and off rapidly. So, I don't think the MOSFET will work for what I'm doing, since it does just that. Does anyone have any suggestions for controlling an analog DC current, so that it won't be changing rapidly in time?

Thanks for the help, guys.

Heating elements usually don't create large magnetic fields, unless it's formed as a coil with lots of turns.

Lefty

#7

retrolefty:

KDanielH:
The system that I am controlling is sensitive to magnetic fields and I therefore cannot have a current controlling the heating element that switches on and off rapidly. So, I don't think the MOSFET will work for what I'm doing, since it does just that. Does anyone have any suggestions for controlling an analog DC current, so that it won't be changing rapidly in time?

Thanks for the help, guys.

Heating elements usually don't create large magnetic fields, unless it's formed as a coil with lots of turns.

Lefty

I will have to check what the allowable change in B-field for my system is, but I do believe it is pretty low.

If it turns out that the MOSFET will not work, do people know of any other methods that might produce a less dynamic current?

Thanks for the reply

#8