Jump to content
Ultimaker Community of 3D Printing Experts

Heated bed no power/ possible electronics failure?

Recommended Posts

Hello everyone!

I recently managed to get self sourced heated bed that is nearly identical to HBK, except the converter board (it is absent). Also i assembled a mosfet key to operate a heated bed's power, but didn't connected it. First I tried to turn bed heating on, without actual power connection, and it turned out, that output voltage was around 0 and corresponding led was also turned off, while ulticontroller was showing target temperature.

I tried a couple of firmwares, and default one, and built using https://bultimaker.bulles.eu/ - all of them showed no errors but no power was present on heated bed terminal.

Is it dead electronics or am I missing something? How can I configure marlin to use second extruder's output for heated bed?

Thanks in advance!

Share this post

Link to post
Share on other sites


How are you going to power your bed since the UMO standard power brick does not deliver enough power.

Now about measuring on the output of the UMO terminals. The UMO has a opencollector output for the heated bed. Without connection anything you will always measure 0V.

The best you can do is to connect a resistor (for example 10K) from the vcc terminal (19V) to the heatedbed terminal

19V -----------

--------| 10K |---- Heated bed connection on UMO board.


And measure with a voltmeter over the 10K resistor. When the bed is on you should measure 19V and when it is off you should measure 0V.

Share this post

Link to post
Share on other sites

Thanks, @zoev89!

I use dedicated 300W 24V industrial PSU for my HB, so my intentions are to use UMO board heated bed connections only to control MOSFET key.

I assembled a test circuit with 10kOhm resistor and a diod, but i used both heated bed connections (as V+ and GND), should I use 19V direct from the power inlet of UMO board to check if 19V is available on the socket? After all, diod on the UMO board near the HB connector is always off too.

Share this post

Link to post
Share on other sites

This is what I was thinking about:


So on the connector there is a 19V terminal and the mosfet output that can pull the other terminal to ground. The 10K resistor now acts like a heated bed and by measuring parallel across the resistor with a volt meter you can see what is happening.

How are you planning connect you heated bed? I have a similar setup a heated bed with 24V power supply and an external mosfet. I used a optical isolator at the time which became redundant when I started powering the UM board from the 24V with a 24->19V stepdown converter.


Share this post

Link to post
Share on other sites

Oh, I see, I did exactly as you explained. When the heated bed is "powered" from the controller, the drain is still in closed state. No connection to the ground, the led is turned off and the voltage is zero.

It is either dead output of my Arduino Mega, or strange behavior of the firmware or some hardware problem of the UMO board (shield) itself. While connection to the +19V from terminal is ok.

Does anyone knows how to build marlin to use second extruder heater's terminal as heated bed's one?

I decide to use https://www.youmagine.com/designs/ultimaker-heated-bed-mosfet-relay-hack-v2 by Jonny Bischof. And after a while I also plan to switch to powering the whole setup with single psu. Which 24 -> 19 V stepdown regulutor do you use?

Share this post

Link to post
Share on other sites

Yuhu! I actually managed to find out where my problem was! It was pt100 with 4k7 setup. Somehow it showed big error and temperature of the bed was around 2°C. And actually firmware is blocking heating without any message. After I heated the bed a little (with a lighter) it started the circuit! Thanks a lot for your help @zoev89! Can you tell me which circuit do you use now to control and power HB?

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Our picks

    • How to 3D print with reinforced engineering materials
      Ultimaker is hosting a webinar where we explain how you can achieve and maintain a high print success rate using these new reinforced engineering materials. Learn from Ultimaker's Product Manager of Materials and top chemical engineer Bart van As how you can take your 3D printing to that next level.
      • 0 replies
    • "Back To The Future" using Generative Design & Investment Casting
      Designing for light-weight parts is becoming more important, and I’m a firm believer in the need to produce lighter weight, less over-engineered parts for the future. This is for sustainability reasons because we need to be using less raw materials and, in things like transportation, it impacts the energy usage of the product during it’s service life.
        • Like
      • 12 replies

Important Information

Welcome to the Ultimaker Community of 3D printing experts. Visit the following links to read more about our Terms of Use or our Privacy Policy. Thank you!