LED flickering on PWM Heatbed?

  • I just found something very strange:
    I have LEDs installed on my printer today. (Power supply: Meanwell HRP-600-24, silicone heating mat with 500 W, Hotend e3dV6, except LEDs otherwise nothing installed)
    If the heating bed is activated in PWM mode, the LEDs will start flickering in sync with the heating bed LED. The power supply would indeed have enough power reserves? When I use M307 to limit the PWM signal for the heating bed (tested with 0.6), the fans of the power supply no longer start to heat up. Is there a solution for this?

  • Have you measured the actual current of the bed at full power? My KEENOVO 500w 120v AC heater pad draws around 4.8A at 120v AC so 580W or so. It may be that your closer then you think to the max of your 600W PSU or even over it you include hotend and motors.

  • Moderator

    Is the heater 24v DC or 120VAC?

  • Heater is 24V DC. Ordered a second HRP-600-24 Meanwell power supply today 😄 Hope this will also improve the print quality due to constant voltage 😄

  • administrators

    That means the power voltage at the Duet is dropping significantly when the bed heater turns on. The most likely reasons for this are:

    1. The output voltage of the PSU is dropping significantly when the bed heater is turned on. Possibly the PSU is overloaded. How much current does your 24V bed heater draw?

    2. The wires between the PSU and the Duet VIN terminal block are too thin, so there is a significant voltage drop across them when the bed heater is on.

    3. The VIN terminal block screws are not tight.

    You can use a multimeter to check the voltage at the power supply output and at the VIN terminal block, with and without the bed heater turned on.

  • As I power the Heatbed over a mosfet (to protect the duet from to much current), I think answer 1 is the problem. I hope with the second PSU this will solve the problem, but I will tell you as soon as it arrives 🙂

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