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Hi all,

This is my first time posting here so if there is anything I don't do correctly please let me know. Thanks!

 

So I am working on adding a DIY heated bed to my Ultimaker Original. I am going the route of basically recreating the HBK on my own. By this I mean I got the aluminum build platform and UM2 style heatbed. The heatbed I got stated it had a 100k thermistor built in. My current design consists of the heatbed powered directly from a 24v power supply which is switched via a Solid State DC relay by the Ultimaker board. I have the relay hooked up to the "Heatbed" screw terminals on the ultimaker board. The thermistor wires are hooked into Temp3 screw terminals. I already soldered in the 4.7k resistor into the R4 position on the board. I tried updating the firmware via the Ultimaker firmware builder but was unsure what selection to choose for my thermistor (from the dropdown menu). I am running into issues with the board not recognizing the thermistor which could be a product of this. The LCD reads 100/0 for the bed and when I try to set a temp for it, it immediately clears it back to 0. I have the board currently detached from the rest of the printer (besides the arduino), and couldn't imagine this would cause any problems, but figured it was worth mentioning.

 

So my question is, what selection should work for the 100k thermistor and 4.7k resistor in the ultimaker firmware builder? Or am I better off using something else to do so. I picked one of the 100k thermistor options from the dropdown, but if I did pick correctly where should I look next as the cause of these problems. Thank you all!!

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Unfortunately barely any two 100k thermistors are alike.  Unlike say PT100s, you need to know exactly the part number.

 

Which of the Marlin builders out there did you use?  I strongly recommend this one:

https://bultimaker.bulles.eu/

 

Note that there are MANY 100k thermistors.  They all have different curves.  Very different.  So hopefully your's is on the list.  If not you are mostly screwed and should buy one that *is* on the list.

 

In theory you could make your own table.  But thermistors are typically under $1 so why bother?  If you want to do your own table you first need to learn to complie marlin yourself (not using bultimaker).  I can help you with that.  Then you have to create your own table.  Trust me - it's easier to use an existing table.

 

 

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Oh.  And you may have hooked up the heater wrong.  First get this temp sensor working.  That's important to get working before working on the heater part.  But I believe the heater terminals on the UMO board output 19V on one side and floating on the other and then when the heater comes on it grounds one side.  This 19V may be too much for your relay - it may blow it out.  Instead you should probably put the proper high voltage connected directly to one side of the relay according to it's specifications (does it take 5V?  12V?  Some other nominal voltage?  Look up the allowed voltage - if you put in too much you can destroy it - it will say what the normal range of voltages that it accepts for the coil side in the specs).  Then you can run a single wire from the relay coil all the way to the UMO board to that pin I mentioned that is sometimes floating and sometimes ground.  Make sure the ground for the power supply goes to some ground pin somewhere on the UMO so the grounds are connected together.

 

Actually if you aren't good at this stuff (maybe you did it properly already) you could draw out a circuit diagram of what you did and photograph it and post it here to ask if it looks okay.

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Hi, 

Thanks for replying. My Relay is good from 3-32v on the input so that should be fine. My wiring was very simple, but you're right I need to try to get the thermistor working first. I was going to use the heatbed output (both terminals) to trigger the relay, which would allow power from the 24v PSU to flow. Here is the link to the bed/thermistor combo I got, I already looked around the listing for more information, but maybe this will give you an idea of what it is. Heated Bed . 

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@theamanjadon  you should start a new thread.  I've seen those tiny holes before.  I'm not sure what causes them but definitely blame the slicer.  Look at the slicer view at those same spots and see if they are non-extruding travel moves with retraction or without retraction.  And you may need to tweak your retraction amount.  You want to retract only enough to relieve the pressure but not actually pull the filament out of the print head at all.  For a bowden printer that is around 4mm but you can just move the E axis from the menu and then manually extrude a bit and then retract until the filament just barely lays down on the bowden (look at the top of the arch).  Then write down how much you retracted manually and use that.

 

Obviously if these holes are at locations where no retraction is occurring then it has nothing to do with retraction.  So first step is to look carefully at what is happening at these spots.

 

 

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@gr5 So after contacting the manufacture to no avail, I started looking at some thermistors. I now see that there are in fact many different options for 100k thermistors. I looked through the list but am having a hard time finding thermistors advertised that are "exactly" the same as those on the list. Like these, these seem to be a pretty standard 3d printing thermistor. Are these the "100k beta 3950 1%" thermistor found on the list?

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