1

Hello all,

Since I modified my 12v printer 3d with a mks gen 1.4 to 24v,
The temperature of my heatbed mk3 is always indicated at minimum 112 ° C, even cold,
I tested 3 different thermistors, and all indicate a minimum of about 110 °,
so I have to ask for a higher temperature to heat …
I measured 1.1 to 1.3 ohm when the plate is stopped, is this the normal resistance for a mk3 in 24V?
Is there something particular to change in marlin to switch to 24v, or a mini temperature?
I have attached pictures of my electricals parts and the configuration of marlin …
In advance, thank you for your advice because I am lost!

alimentation.jpg
alimentation.jpg3032×1788 134 KB
mk3.jpg
mk3.jpg2736×3464 483 KB
mk3-thermistor.jpg
mk3-thermistor.jpg2288×2960 277 KB
thermistor-power.jpg
thermistor-power.jpg3379×2292 496 KB

1 Like
2

Did you verify that the correct thermistor type is selected in the firmware, I assume you are using Marlin?

You have to choose the right thermistor from the list that is provided in the firmware. Also your configuration has not been uploaded.

3

Hello Zapaer,

Yes i put the : #define TEMP_SENSOR_BED 1
because it’s an SMD thermistor 1206

there’s something esle to change in marlin?

4

You need to figure out what the resistance of your thermistor is (10, 100 or 200k).

5

You can measure the rated resistance for your thermistor using a multimeter, this video - YouTube might help.

6

Normally it’s a 100k, and i had just mesured 134 kohm it is normal?..but it seems to work, if i test the thermistor in another card she give me a good temperature… may be there is something else to change between marlin and the mks gen 1.4?

7

I think 134 is within the okay limit. Maybe just try switching to different 100k sensors on the firmware and see if that works for you.

If you just changed the heatbed, I don’t see how it would affect anything else. You mentioned you used 3 other thermistors, were they all the same type?

8

Also try connecting the heatbed thermistor to the hotend on the mks gen 1.4 and see if you have the same reading. Maybe there is some damage to the mks gen 1.4 board.

9

Hello Zapaer,

You’re right, my mks gen 1.4 board is damaged, as E0 (pin 13) and Bed (pin 14) given me false temperatures…

I had change this line in Marlin pins.h:

#define TEMP_BED_PIN 15 // ANALOG NUMBERING

and put the thermistor on E1

and now everything is ok!!!

Thanks a lot, i whish someday i understand how to test them with a multitester!!

have a good day

10

Great, I’m glad it works for you now.