can multiple PWMs be controlled simultaneously by one PIC?
can multiple PWMs be controlled simultaneously by one PIC?
(OP)
I was wondering if anyone has used a microcontroller (preferably PIC) to control multiple PWMs which are used to control 4 heating elements. I would like to do this with as few chips as possible, hopefully 1 PIC. The project requires that each heater be monitored and controlled separately. Any ideas would be greatly appreciated.





RE: can multiple PWMs be controlled simultaneously by one PIC?
RE: can multiple PWMs be controlled simultaneously by one PIC?
Dan
Owner
http://www.Hi-TecDesigns.com
RE: can multiple PWMs be controlled simultaneously by one PIC?
RE: can multiple PWMs be controlled simultaneously by one PIC?
Bit banging will let you get away with a cheaper Pic.
RE: can multiple PWMs be controlled simultaneously by one PIC?
RE: can multiple PWMs be controlled simultaneously by one PIC?
Dan
Owner
http://www.Hi-TecDesigns.com
RE: can multiple PWMs be controlled simultaneously by one PIC?
You must remember temperature is really a pretty slow process... Your sensors can't even tell anything has happened for a few seconds... And as you know a micro can do a whole lot of things in a single second.
RE: can multiple PWMs be controlled simultaneously by one PIC?
RE: can multiple PWMs be controlled simultaneously by one PIC?
The response time of the system can be at about a tenth of the inertia. So say 10mS per I/O update. See how much can be done with a given micro within 10mS.
RE: can multiple PWMs be controlled simultaneously by one PIC?
Also I have never heard of any application that monitors the heating element! Normally no one cares about the element, they are trying to heat a space or an object up, not the element. This means they are trying to monitor the temperature of the object which itself needs time to absorb the energy and actually heat up. Again meaning what's the *big* rush.
RE: can multiple PWMs be controlled simultaneously by one PIC?
In 100ms, a PIC running on a 20MHz crystal will be able to process 500,000 instructions. The trick is, getting an A/D converter that will give you the response time you need, assuming that's the method you're going for. The A/D on the PIC will be in the range of ms/sample/channel, and that may not be fast enough if the element can change 1400 degrees/s.
Dan
Owner
http://www.Hi-TecDesigns.com
RE: can multiple PWMs be controlled simultaneously by one PIC?
Every so often, bump up the duty cycle a few percent, continually checking the temp. If it's too hot, bump it down a few percent. Do this over a long period, say 500ms. In other words, find a comfortable set point, and make slow changes over long periods of time...
Dan
Owner
http://www.Hi-TecDesigns.com
RE: can multiple PWMs be controlled simultaneously by one PIC?
RE: can multiple PWMs be controlled simultaneously by one PIC?
RE: can multiple PWMs be controlled simultaneously by one PIC?
So do think outta the box and study your scheme before grabbing multiple CPUs. You still may have to. Then just use the sychronous ports.
RE: can multiple PWMs be controlled simultaneously by one PIC?