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heated bed upgrade on um 1 - software issues?

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Posted · heated bed upgrade on um 1 - software issues?


I have an off the shelf heated bed for a reprap machine and I wired it into a um1. Naturally It's not working and I'm pretty certain its the software rather than the hardware.

There are 4 wires in total. Two are the heating element wires plugged into the heated bed on the main board.

And there are two wires for the thermister, one red, one black, vcc and signal I assume.

I upgraded the firmware and tried all permutations of wiring. It's definately wired correctly, but I see no lights for heating up the device on the mainboard. I can set the bed temperature but there is no change from 0. I even tried using one of the ultimaker extruder sensors and it doesnt read that either. Now the two thermister wires are wired into the small splitter thingy from the extruder.

Assuming the hardware I received is fine, i can only assume the um1 software simply does not work. oh the bed also runs on 12 volts so it should totally work with the board.

Has anyone gotten this to work?


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    Posted · heated bed upgrade on um 1 - software issues?

    You should concentrate on getting the temperature reading to work. Do you know what kind of thermistor you got with the kit? The software you need is here - but you have to choose a thermistor:



    Once you get the hex file you can use cura to install it.

    Also you need to install a 4.7K resistor. Did you do that step?

    This post shows a photo of where the resistor goes and how to hookup a typical (but the heat side of things are all different) heated bed:


    By the way, the UM typically puts out 19V, not 12V and most people use a separate power supply for the bed, but you don't necessarily have to and one thing at a time.


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    Posted · heated bed upgrade on um 1 - software issues?

    Most likely, the UM1's power supply and the controller can't handle the addition of a heated bed.

    I helped another UM1 owner set up one. You might find some useful information here:


    Just to give you an idea. Most beds draw at least 10 amps. At 12V that is 120watts. The UM1's PS is 120watts for everything. And that doesn't consider that the UM1 board will overdrive the bed at 19V. At 19V it will draw about 300watts and 16amps and will probably be well over it's rating.


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    Posted · heated bed upgrade on um 1 - software issues?

    Don't forget the 4.7k Ohms resistor you need to solder into the mainboard!

    This would be "R4" for Sensor "Temp3".

    R4 is one of the three empty spaces just above the temperature sensor connectors on the mainboard (UM electronics 1.5.7), it is marked on the board.

    Any 4.7k Ohms, 1/4 Watts, 1% tolerance resistor will do, such as this one.

    You can usually find these in most RepRap shops, too.


    George already mentioned that, sorry...



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