MK2A Heated Bed causes board to crash
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@bdelia said in MK2A Heated Bed causes board to crash:
I have confirmed that the bed I have is dual voltage via the same wiring from the seller. I have been able to AutoTune the heated bed, but had to lower the PWM to 20% during the tuning, then I was able to increase that value back up after tuning and all seems to be working. I will keep my eye on it but I am happy with where I am at right now.
I think you have a fire hazard on your hands here. Does it make sense to you that you have to reduce the PWM to 20%?
It's far more likely that the bed is 12v only and you're feeding it 24v.
Can you post a photo of the bed and a close up of the terminals?
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@bdelia It looks like it is wired for 12V. Connecting to 24V makes 4x the power, that is why You had to lower the max pwm so much.
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I have been able to get past this. I only have to run the initial autotune with the PWM lowered. Once done I can raise the PWM value back to 1.00.
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If the bed is wired for 12v it would be better to re-wire it for 24v. If you upload a picture of the bed and wiring maybe we can advice on how/if/etc
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@bdelia said in MK2A Heated Bed causes board to crash:
I have been able to get past this. I only have to run the initial autotune with the PWM lowered. Once done I can raise the PWM value back to 1.00.
does it not bother you that 3 people think that your bead is wired for 12V as this explains why you have to lower your pwm?
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Yes, I little. However, I have done my due diligence and contacted the seller, Zyltech, and have confirmed this board is a dual voltage bed as I believe I have mentioned already.
Is there a way to confirm this with a multi-meter or other mechanism?
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post a picture of the backside.
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@bdelia said in MK2A Heated Bed causes board to crash:
Is there a way to confirm this with a multi-meter or other mechanism?
disconnect the wires from the bed terminal and measure the resistance across them
and sure, it can be dual voltage, but its not automatic
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@bearer said in MK2A Heated Bed causes board to crash:
@bdelia said in MK2A Heated Bed causes board to crash:
Is there a way to confirm this with a multi-meter or other mechanism?
disconnect the wires from the bed terminal and measure the resistance across them
and sure, it can be dual voltage, but its not automatic
I appreciate everyone's help on this and guidance. I will check resistance once I get back to the house. If I recall I believe the resistance was 1.7Ohms when I initially checked.
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https://reprap.org/wiki/PCB_Heatbed site suggest 1.7 is for 12v beds, but they also say the size of the MK2A is smaller there. anyways it also has pictures showing how the dual voltage beds have different connections for 12 an 24v. might be helpful
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@bearer said in MK2A Heated Bed causes board to crash:
https://reprap.org/wiki/PCB_Heatbed site suggest 1.7 is for 12v beds, but they also say the size of the MK2A is smaller there. anyways it also has pictures showing how the dual voltage beds have different connections for 12 an 24v. might be helpful
I just double checked resistance, it reads 1.6Ohms.
I will review the specs on the page you shared. When I talked to the seller they said that this bed gets wired the same regardless of 12V or 24V. I will also contact them again and let them know the resistance I am getting and see if they feel that I have a defective bed or not.
Here is a picture for their website of the board I have for reference.
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@bdelia at 1.7Ohm it would draw just over 14A of current!
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that is defiantly not a dual voltage bed.
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@bdelia According to reprap wiki - MK2b Dual power is what you expected. MK2a seems to be be a single power heatbed (and probably 12V). And in general dual power heatbed has 3 solder pads.
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however something is still wrong here.
a 600W meanwell power supply should be able to handle that.
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Perhaps the wire is too thin, and passing 14A+ (14A is bed alone) causes significant voltage drop.
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yes. you would need a 2mm^2 wire for that.
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@Veti said in MK2A Heated Bed causes board to crash:
2mm^2
I am using 14Gauge wire from my external Mosfet to the Bed.
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If you set your multimeter to read resistance and then short the two probes together, what reading do you get? You need to subtract that reading from the 1.6 ohms that you measured.
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@dc42 said in MK2A Heated Bed causes board to crash:
If you set your multimeter to read resistance and then short the two probes together, what reading do you get? You need to subtract that reading from the 1.6 ohms that you measured.
When I read resistance by shorting the MultiMeter leads it reads .2 Ohms. So, if I understand you then that would mean my bed resistance, if measured at 1.6 is really 1.4 Ohms?
If the above is accurate then it seems the bed is on the fringe of 24V compatible? Does that sound correct?
