MK2a thermistor of heatbed resistance?

Stunzasr20
Posts: 28
Joined: Tue Nov 03, 2015 4:17 am

MK2a thermistor of heatbed resistance?

Post by Stunzasr20 » Tue Feb 16, 2016 2:37 pm

HI
Just wondering if there should be any resistance between the 2 wires on the MK2a thermistor on the heatbed?
I tried testing but got no result.
I am thinking there should be resistance between these 2 wires.
I am wondering because I am not able to get a reading from my multimeter, and just switching the printer on and sitting there idling (not printing or moving etc) the LCD tells me that the heatbed is 46 degrees Celcius, which i highly doubt!

Attached is the screenshot to show basically what I mean,

Weirdly if I manually turn on the heatbed in Repitier Host, it appears the left side of the LCD (which I thought was the extruder temperature) slowly increases. The right side remains the same 45/95. The extruder does not get hot. The heatbed does get hot. The LED between the 2 heating wires on the heatbed illuminates yellow
Any suggestions appreciated.

Sherry
Posts: 362
Joined: Wed Jul 01, 2015 12:52 pm

Re: MK2a thermistor of heatbed resistance?

Post by Sherry » Tue Feb 16, 2016 4:14 pm

Stunzasr20 wrote:HI
Just wondering if there should be any resistance between the 2 wires on the MK2a thermistor on the heatbed?
I tried testing but got no result.
I am thinking there should be resistance between these 2 wires.
I am wondering because I am not able to get a reading from my multimeter, and just switching the printer on and sitting there idling (not printing or moving etc) the LCD tells me that the heatbed is 46 degrees Celcius, which i highly doubt!

Attached is the screenshot to show basically what I mean,

Weirdly if I manually turn on the heatbed in Repitier Host, it appears the left side of the LCD (which I thought was the extruder temperature) slowly increases. The right side remains the same 45/95. The extruder does not get hot. The heatbed does get hot. The LED between the 2 heating wires on the heatbed illuminates yellow
Any suggestions appreciated.
hi,
1.please tell me ther printer type and mother board.
2.according to you description, it is largerly because you connect thermistor cable of heat bed to extruder thermistor socket on motherboard. please if those cables connection are correct.
3.the MK2A resistance is 1-2ohms,make sure you meansure the resistance correctly.please refer to the post
http://www.geeetech.com/forum/viewtopic ... 19&t=17039
4.regarding to the problem "The right side remains the same 45/95".
please Checking if the T_HE1, T_HE2 and T_BED sockets on PCB are fine.
(1)Make sure you burnt correct geeetech firmware.
http://www.geeetech.com/forum/viewtopic ... 20&t=17046
(2)Make the T_HE1, T_HE2 and T_BED open circuit, short circuit and plug 100k thermistors on the three sockets. Checking if the corresponding temperature is normal. You can refer to the post
http://www.geeetech.com/forum/viewtopic ... 23&t=17030
1.png
1.png (51.53 KiB) Viewed 7022 times
The normal situation is as below while the hot ends and hot bed cool down.
QQ截图20160216161342.png
QQ截图20160216161342.png (5.46 KiB) Viewed 7022 times

Stunzasr20
Posts: 28
Joined: Tue Nov 03, 2015 4:17 am

Re: MK2a thermistor of heatbed resistance?

Post by Stunzasr20 » Tue Feb 16, 2016 6:00 pm

Hi Eric
1. Geeetech Aluminum Prusa I3, with Sanguinololu board.
2. I retested and applied a little more force to the connection, attached should be the picture of what I was asking. I now have a reading and it is shown in both cases on the multimeter within each picture. Thermistor appears to be 4.53K ohms.
According to the Geeetech instructions/pictures of the printer on page 36, the wires for thermistor of heatbed are the thinner gauge wires and connect with a pre-fabricated clip (not the screw in items that are called heating wires for heatbed, as pictured within the instructions).

3.Heating wires for heatbed showed 1.8 Ohms, as per photo
4. Does that apply to my case, with Sanguinololu board. I cant see any similar labelling

Just a thought, could the polarity on either connection on the board matter?
Attachments
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Mark
Posts: 1553
Joined: Thu Aug 06, 2015 9:19 am

Re: MK2a thermistor of heatbed resistance?

Post by Mark » Tue Feb 16, 2016 8:25 pm

It is the same method for your sanguinololu board, check if you have wrongly connected the thermistors.

Stunzasr20
Posts: 28
Joined: Tue Nov 03, 2015 4:17 am

Re: MK2a thermistor of heatbed resistance?

Post by Stunzasr20 » Thu Feb 18, 2016 8:31 am

I am of the belief that it is correctly wired. Can you confirm the resistance of the thermistor for the headbed?

Mark
Posts: 1553
Joined: Thu Aug 06, 2015 9:19 am

Re: MK2a thermistor of heatbed resistance?

Post by Mark » Thu Feb 18, 2016 3:55 pm

the resistance of the thermistor is about 100k at room temperature, and it will change according to the temperature, but you can measure the voltage between the pins of the thermistor connector, it should be 5V powered on with USB. And when you do the open circuit test for the thermistor connectors on the board, did you get 0 and 358?

Stunzasr20
Posts: 28
Joined: Tue Nov 03, 2015 4:17 am

Re: MK2a thermistor of heatbed resistance?

Post by Stunzasr20 » Thu Feb 18, 2016 7:21 pm

The open circuit test showed me 0/0 0/45

Mark
Posts: 1553
Joined: Thu Aug 06, 2015 9:19 am

Re: MK2a thermistor of heatbed resistance?

Post by Mark » Thu Feb 18, 2016 8:24 pm

well in this case the mainboard might be dead, BTW, are all the other functions of the printer working or not?

Stunzasr20
Posts: 28
Joined: Tue Nov 03, 2015 4:17 am

Re: MK2a thermistor of heatbed resistance?

Post by Stunzasr20 » Thu Feb 18, 2016 8:48 pm

From what I understand other functions are working. For example I can load a stl. file and use rep host to generate the path (g code) and it runs pretty much how it should (that is after I remove in the Gcode editor the heating function section. So basically it does most things but extrude.

By mainboard are you referring to PSU or in my case Sanguinololu control board?

Mark
Posts: 1553
Joined: Thu Aug 06, 2015 9:19 am

Re: MK2a thermistor of heatbed resistance?

Post by Mark » Thu Feb 18, 2016 8:51 pm

the sanguinololu board, not the PSU.

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