Depending on how accurate and robust you want the end product, many factors will need to be considered when designing an optical pyrometer and temperature control "system".
Before redesigning the wheel, I would familiarize oneself with current optical methods for temperature control, then also consider that you will be driving a transformer load which can be tricky if you want smooth phase angle control vs "bang bang" on-off control methods.http://www.ebay.com/itm/Phase-Angle-SCR-Driver-Board-with-Current-Limit-for-large-SCRS-Inductive-loads-/162023259453?hash=item25b956bd3d:g:OuQAAOSwAvJW-~JO
Coding a good PID loop or fuzzy tuning algorithm can also be a bit tricky.
Fortunately the temperature control component to do this with PID as well as autotuning has been available off the shelf for $10 to $15 USD. http://www.ebay.com/itm/SSR-220V-Digital-PID-Temperature-Controller-Thermocouple-K-Dual-LED-Display-/222371957216?hash=item33c666c9e0:g:8RgAAOSwEzxYSnXJ
You need also to consider that if the optical device is not well focused on the target or if someone bumps the optical input device away from the target, the temperature control loop will be fooled into thinking the temperature is just low and will need more power. This can be dangerous and will require special handling in the coding to prevent large accidental over temperature problems. If the scanning method is used, it will need mechanical control as well as a method to keep the controlled area of interest as the target area, some auto tracking method. IMO, a contact measurement method might be less costly, safer and easier to implement, although the non contact scanning method can have some advantages at the sacrifice of absolute accuracy.
I spent a good portion of my adult life designing such uP based controllers as well as contact and non-contact measurement methods, and indeed there are pits ahead to be avoided, therefore requiring some forethought. It can be done, and yes it can be done with Arduino and other platforms if you've got lots of time
on your hands for coding and debugging the mechanical scanning interface as well as the temp control methods.
Just purchasing and mating a IR sensor to an Arduino is the easiest part.
Edit: Looking over the data sheet on the MLX90614, it seems like a good choice for the task in it's present conception.
« Last Edit: 2017-01-17, 16:51:41 by ION »
Just because it has a patent application or is patented does not always mean it really works.