Ideas for software temperature control.

Post improvements made for UP, and share ideas.
Robin
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Joined: Sat Dec 29, 2012 6:59 pm

Re: Ideas for software temperature control.

Post by Robin » Sun Sep 29, 2013 12:59 pm

Michael_K wrote: Nope!
Thanks for clearing that up for me. I would have sworn I looked the chips up and buzzed the circuit out, but when you get to my age I guess you just can't depend on the old noodle anymore.

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Michael_K
Posts: 19
Joined: Sat Aug 17, 2013 8:12 pm

Re: Ideas for software temperature control.

Post by Michael_K » Sun Sep 29, 2013 5:36 pm

My english is not so good... so I didn't understand half of your message, sorry.

But if you want more detailed answer here it is:

There are two SMPSU on the main board, but none of them relates to the heater.
Heater is powered directly with a voltage from outer power supply (about 20V in my case).
CPU controls the extruder temperature by measuring it and switching heater on/off with a MOSFET switch (quite fast).
CPU actually regulates the temperature - you can see it by watching the led (marked DO3 on my board), you can notice fast blinking or at least changhing the brightness when the temperature reaches the point.
You can also guess that it regulates the temperature even without opening the case as it has a different settings for ABS and PLA, moreover these settings may vary with software (v1.15 uses lower temperature for PLA, for example).

Robin
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Joined: Sat Dec 29, 2012 6:59 pm

Re: Ideas for software temperature control.

Post by Robin » Sun Sep 29, 2013 6:15 pm

Michael_K wrote: There are two SMPSU on the main board, but none of them relates to the heater.
Maybe your printer is different?
Mine is a model H479

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Michael_K
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Joined: Sat Aug 17, 2013 8:12 pm

Re: Ideas for software temperature control.

Post by Michael_K » Sun Sep 29, 2013 8:14 pm

Hmm... Maybe.
My printer is "UP! mini" and it's marked as 3DP-10-4A
And the main board is marked with V20 label

Board looks very similar to this:
http://www.pp3dp.com/index.php?page=sho ... &Itemid=37

It has some minor differences like metallized mounting holes, places for some additional capacitors for power lines (not mounted though), microSD instead of SD-card and so on.

To be honest, I don't think it has significant differences in schematic or operating logic.
But... who knows..

Robin
Posts: 113
Joined: Sat Dec 29, 2012 6:59 pm

Re: Ideas for software temperature control.

Post by Robin » Mon Sep 30, 2013 8:20 am

If you use the CPU to control a heater you must worry what happens if the CPU dies with the heater ON. Does it all catch fire?

So you add circuitry to stop run-away heating. A crowbar circuit is the obvious option but that means changing a fuse.

If you allow it to switch on again when it cools you have created a thermostat.

To avoid possible radio frequency switching you must either filter out the switching spike then add hysteresis, or, use a switch mode PSU which has a set minimum on/off period.

If you trace the circuit I think you may find this is the reason your UP has 2 switch mode PSU's.

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Michael_K
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Re: Ideas for software temperature control.

Post by Michael_K » Mon Sep 30, 2013 8:37 am

I just described the original pp3dp pcb and original behaviour of pp3dp software/firmware.

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