1
$\begingroup$

I'm using a 200x200 mm PCB Mk2B which connects to the MOSFET of the D8 pin on a RAMPS 1.4 shield. I used 12 V power source for heat bed so I connected positive to pin 1 and negative to both pin 2 & 3 of the bed. Heat bed worked properly. But the wires that connects power source to power supply pin on RAMPS were being heated badly. I think the problem is come from heat bed because when I unplugged heat bed, wires were cool down instantly.

Can someone helps me with this problem. I'm just a newbie in this area.

Improve this question
$\endgroup$
3
  • $\begingroup$ Its normal for the wires in a 12v system to get hot. What was the bed temp? how long was the print? $\endgroup$ – user77232 Mar 16 '20 at 15:34
  • $\begingroup$ The bed temp is 60 degree. The wires were getting hot just after the print begun. But replaced the wire with a thicker ones had solved the problem $\endgroup$ – DrPortgas Mar 18 '20 at 9:33
  • $\begingroup$ What AWG did you use? (NB: it supposed to be printed on the cable) $\endgroup$ – user77232 Mar 18 '20 at 12:39
1
$\begingroup$

The PCB heatbed Mk2B has a reported resistance between 1.0-1.2 Ω. The current that is drawn from the power supply equals about 12/(1.0 or 1.2) = 10-12 A. Note that this amount of current requires cables that can carry that load, too thin cables heat up.

Note that you have wired the bed correctly for 12 V (see image below), the wires might have a too-small cross-section, try thicker wires. Personally I use AWG 12-14 silicone wires depending on the bed resistance.

Mk2B heatbed connections

AWG 12-14 size silicone, multiple threads (these are the best for the bed because they are more flexible), should be able to handle the load fine. Note that cables also have resistance; if there are heat spots in the cable or the connection, this indicates that the cable may be broken or the connection has too much resistance.

Improve this answer
$\endgroup$
3
  • 1
    $\begingroup$ Yes, the heat spots were indicated in the cable. I will replace its with a thicker ones. Thanks for your help $\endgroup$ – DrPortgas Mar 17 '20 at 1:57
  • $\begingroup$ @DrPortgas, don't use that machine again until you replace that cable. $\endgroup$ – user77232 Mar 17 '20 at 12:38
  • $\begingroup$ yes, i had replaced the cable and its works very well. Thank a lot $\endgroup$ – DrPortgas Mar 18 '20 at 9:29
1
$\begingroup$

Check the diameter of the cable. The smaller the diameter the higher the resistance, thus the heat. AWG14 seem a bit small.

Improve this answer
$\endgroup$
2
  • $\begingroup$ Sure, i will check again the diameter of the cable $\endgroup$ – DrPortgas Mar 17 '20 at 1:58
  • 1
    $\begingroup$ 14 awg should be sufficient. Moving to 12 awg won't really reduce the heat. $\endgroup$ – user77232 Mar 17 '20 at 12:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.