Thermal Test Results
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Yes I plan to raise the maximum allowed current closer to the driver's rating of 2.8A. However, the driver has a maximum continuous rating of 2A when the motor is stopped in the half step position, so it is mandatory to implement standstill current reduction before we increase the allowed current.
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Might also be worth in light of my rather stupid "should know a lot better" experience on connectors on the 0.8.5 board to include some sort of warning about using high quality properly rated connectors to connect to the pin headers…. I've personally really only considered pin headers good for around 1A of current despite the pins being rated way above that.
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Hi Phil
Good point, we are planning on including female connectors in all the production boards we send out which claim a 4A rating per pin.
Cheers
Tony
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It might be interesting to see what will be the temperatures with a fourth driver active and the board placed vertically (maybe aside a plate at a fixed distance), which will improve natural cooling without the need of any forced cooling.
Anyway, it seems the board don't need forced cooling, but I assume the tests were done in 'open air', board horizontal ? what was the distance from the support ? -
The tests were done with the board horizontal, on an heat resistant antiseptic pad (ie no support). Effectively the worst case scenario for getting heat away from the underside.
The 4th and 5th drivers being on will not significantly increase the heat across the 3 drivers tested, as you can see the Z driver is the hottest by a small fraction on most occasions and it is on the edge of the board.
For most applications forced cooling should not be required. If the current is pushed over 2A to the max of 2.8A I would expect forced cooling and heatsinks to be required (which is why we have limited it to 2A so far).
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Just a quick comment as I've been speaking seemingly the most about force cooling…. I'm planning for summer time where in my non air conditioned garage temps will easy get into the high 30's and mid 40's (celcius) and air flow becomes critical. I'm hoping to be back printing in the next few days and will hopefully grab some thermal images as well.
Question for Tony: Over what time frame was the heat cycle? what happens after 3-4-6 etc hours?
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Hi Phil
Andy let the temp stabilise for 20 minutes before taking the picture, not sure how long they were running to get up to a stable temperature. Once at a stable temp though I don't think there is any benefit to leaving it for hours.
Cheers
Tony
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A couple of images about 2 hours into a print
Ambient Temp @ 10c
PCB mounted in case with forced air cooling.
Lid had been sitting over top but not screwed down.
XYZ @ 1.6A
extruder @ 1.3AThe images are more dramatic due to the low surrounding ambient temps.
Image: centre of board shows 18.2c, note my PCB heater is SSR controlled.
Image 2: close up of the hotter spot to the right (middle) of the drivers, but really the heat seems to spread out quite well with the drivers themselves being no hotter than the pcb average and can obviously handle more current.
I just happened to be taking these as the print finished so Image 3 is within a couple minutes of it ending and you can see the heat has already bleed away with the fan cooling from underneath.
If i get time tomorrow I can up the currents to 2A and test if anyone is interested.
All in all very good really but at least for me my board(s) will be fan cooled.
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Hi Phil
Those are super helpful! Really interested in seeing how it goes with 2A and a fan.
Interesting how the hot spots are not on the tops of the chips. Is it possible the thermal and image are slightly mid aligned on your camera?
Cheers
Tony
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You can tell really clearly from the stepper wiring runs that the thermal and image aren't matched up.
I really need a FLIR camera…
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Hi Tony and RC,
RC… mmm yeah nice spot, i'll check the alignment today, I wonder if this is caused by the closeness of the camera. the FLIR uses two lens.
Based on the misalignment the hot spots are centred on the IC'sJust rest the driver currents to 2A as i type this and running auto cal a couple times and will then quick off a print....
Learning to slice files for a 0.6mm nozzle as i do this.... (must update frustration thread later)
Cheers
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OK. the offset seen in the images about equals the lens spacing on the FLIR camera so the hot spots are actually the IC's.
Ambient at time : @ 16c
Current xyz: 2A
Print duration at time: 1HrImage 1:
Case lid still sitting on top, really only just above ambient so very little heat radiated upwards it would seem
Image 2:
Close up of the drivers, the thermal image needs to shift to the right. look like around 34c rise above ambient
It should be noted that the air exiting the case does not even feel warm.
Also i placed a finger on the IC and PCB to see what it actually felt like and it certainly didn't feel like 50c. -
I hope I don't offend you by saying this, Aussiephil, but are you sure that you have the device calibrated properly? From what I know, they are not always absolutely accurate, but relatively accurate, and therefore need to be calibrated. Can you shed some light on your process for ensuring these temperatures are absolutely accurate?
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@bot:
I hope I don't offend you by saying this, Aussiephil, but are you sure that you have the device calibrated properly? From what I know, they are not always absolutely accurate, but relatively accurate, and therefore need to be calibrated. Can you shed some light on your process for ensuring these temperatures are absolutely accurate?
No offence taken.
Certainly the FLIR thermal imaging devices and software are not laboratory grade equipment and the reading should be taken with some allowance for error however they remain quite indicative.
Whilst i didn't baseline these particular readings apart from some basic ambient temperature measurements I have taken a whole range of measurements of other things in the 0-100c range that have been verified against other measurement devices and with under 1c variance between devices so I would have a relatively safe assumption that the numbers are well in the ball park.
I recognise that well in the ballpark may not be good enough for some.
Cheers
Phil -
Heck, even within 5 degrees is close enough for me. Thanks! Looks like the drivers remain quite cool.
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Phil 51C at 2A, with your lower ambient temp and airflow does not sound unreasonable compared to our results. That's for doing the additional tests, it will be interesting to see in 6 months time when your ambient temp is slightly different!
