# 12V 20 ohm Heating Mat

Posted by unialpha
 12V 20 ohm Heating Mat September 14, 2021 10:44AM Registered: 8 months ago Posts: 1
Hey guys, I'm having trouble when connecting this heating mat to my printer:

[uk.rs-online.com]

it's 12V so I connect it directly to the D8 port in the RAMPS board. The problem is that although it should be able to reach 300ºC according to the datasheet, I am only able to heat it up to 50ºC with the printer. I think it might be do to its resistance (20 ohm), since heating cartidges are usually 10-15 ohm, so this mat needs more current. In case my hypothesis is right, is there a way to supply it with more current? I mean with the RAMPS itself, I know I could install an external mosfet.

#define PID_MAX is already set to 255

Thank you

Edited 1 time(s). Last edit at 09/14/2021 10:44AM by unialpha.
 Re: 12V 20 ohm Heating Mat September 14, 2021 11:10AM Registered: 2 years ago Posts: 210
Quote
unialpha
Hey guys, I'm having trouble when connecting this heating mat to my printer:

[uk.rs-online.com]

it's 12V so I connect it directly to the D8 port in the RAMPS board. The problem is that although it should be able to reach 300ºC according to the datasheet, I am only able to heat it up to 50ºC with the printer. I think it might be do to its resistance (20 ohm), since heating cartidges are usually 10-15 ohm, so this mat needs more current. In case my hypothesis is right, is there a way to supply it with more current? I mean with the RAMPS itself, I know I could install an external mosfet.

#define PID_MAX is already set to 255

Thank you

The D8 RAMPS port can output 11 amps at 12 volts, so that's not the problem. The problem is that your mat has a resistance of 20 ohms, so it draws only 12/20=0.6 amps. 0.6Ax12volts=7.2 watts.
About as much as a Christmas tree bulb. 50C sounds about right. It's a silicone mat (apparently) so it should be able to survive exposure to 300C, but it isn't likely to get anywhere near that temperature running on 12 volts.
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