Another Heated bed Issue

[mclain 0]

Hi there,

Earlier this year i bought myself the ultimaker. Played with it, liked it, but wasnt happy with the ABS results. Soafter i moved, i installed everything again and made myself a new aluminium bed. Put a heatplate on it and voila. A heated bed. Tested it with a power supply and its working sweet. But now i wanted to hook it up to the ultimaker. So i installed a relay, hooked up the power supply and the heated bed, installed a Thermister, hooked everything up to the ultimaker board(heater3 and Temp 3).

But it was reading 0 celcius.. So i figured out that this was an firmware issue. So thanx to the magic Marlin build tool, i compiled myself a new firmware where my sensor was configured. I could now red the temperature. Although its about 10 degrees of, it is measuring the temp. But when i input my wanted temp for my bed, nothing happens. I see no light on heater 3 output, nor is my relay being enabled.

I installed it in the heater 1, and the relay setup works fine.

I looked at the marlin tool again and couldnt see anything there that i figure needed to be enabled to get the heater 3 going.

So now i'm kinda stuck. Anybody got an idea?

[mrjohnk 0]

Did you happen to install the 4.7K resistor to the board? It is required in order to read the thermistor correctly.

-John

[mclain 0]

My readout is only 7 degrees of.

Installed the 4k7 on the board for sensor 3

[mclain 0]

Nobody?

[beeone 0]

I am having this problem too with more or less the same setup. I have a relay hooked up to the heater output and soldered on the 4.7k resistor and attached an epcos 100k thermistor. I built the firmware using the online marlin builder. Now the first problem is that it's showing 1.6 degrees for the temperature, which is about 20 degrees off. The second problem is that it's not activating the relay so nothing happens. Any ideas?

[am001 0]

I found in the cold weather that if the heater bed is too cold, the firmware seems to assume it is an error and won't turn it on. Your offset error could be producing the same effect.

I pointed the workshop fan heater at the bed for 30 seconds, and once it registered > 5 or so degC it would suddenly work.

I also find that at low temps it is inaccurate, but near operating temp, 50-70degC, it is very close, which is what matters.

[beeone 0]

Mine is way off even when the temp is higher, when it's showing 50C in reality it's close to 100C. I have an adjustable power supply hooked to the heated bed so I can control the temp with that so at least I'm able to use the bed.

I now have a heated chamber too as just the heated bed was causing horrible cracking on larger parts.