Request: Mosfet PWM heater cricuit

Hi all,

I am looking for a simple schema for a mosfet based heater that can be used with the PID library..

Who can help me out??


quoted from Triffid_Hunter
'I use the IRL3803 for my heater, much simpler than this- arduino pin -> gate, gnd -> source, heater -> drain.. no other parts needed'

Is this workable and can it be used with PID and does PID exist in the firmware, I forgot to check this..


Right now I am having a heater schema with a relay and this is on or off and the temperature goes up and down by 20-25 degrees celcius..I guess this doesn't do any good in stable printing..


So please help me out :-)


With kind regards and thanks in advance !!

Michael



with kind regards..

Just copy the heater circuit from this version of the RepRap electronics: [objects.reprap.org]

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[www.hydraraptor.blogspot.com]

mhensen Wrote:
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> Right now I am having a heater schema with a relay
> and this is on or off and the temperature goes up
> and down by 20-25 degrees celcius..I guess this
> doesn't do any good in stable printing..
>
>
> So please help me out :-)
>
>
> With kind regards and thanks in advance !!
>
> Michael
>
>
>
> with kind regards..


This is probably due to a combination of the mechanism used in the software to enable and disable relay and the thermal mass of the heater head.

Basically you need it switching faster.

If you are talking about the extruder, the Extruder Controller firmware implements the PID loop. The "B" output of the Extruder Controller board is an analog (PWM) output.

If you are talking about a heated build platform, the Extruder Controller also implements the PID loop for that but the "A" output of the extruder controller board is a binary (0/1) output so it turns ON for values of 128 or more and OFF for values below 128. I find it tends to settle at 2 or 3 degrees below the setpoint.

There is probably a PID library (or several) for Arduino. The hard part is tuning the parameters.

as far as tuning PID goes, doing it "properly" is quite hard, but fudging it gets you pretty close and can be fun.. basically, the P parameter is your basic 'head towards target' multiplier, the D parameter (usually negative) impedes how fast the heater approaches the target by cutting power if it gets too quick- as well as impulse response, and the I parameter is long-term fine tracking. the I limit is equally as important as the I multiplier, and they should be tuned in concert with one another.

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Wooden Mendel
Teacup Firmware