I can not operate the heatbed with ramps and arduino mega 2560 1.4

I have a 1.4 RAPS with arduino mega 2560 and heatbed Mk2A and a source of 28A.

I can not get him to the heatbed current, use the sprinter and prontface, I'm in the process of setting up the printer and can not get the voltage output of the Ramps D8.

I have 100k thermistor and the prontface if you check the temperature, and if you put a hand on temperature rises, at rest as well as the brand of the extruder


any idea what could be.


thank you very much.

have you got both of the power plugs connected? (the green connectors)

Edited 1 time(s). Last edit at 05/30/2013 09:54PM by waitaki.

yes, I think it may be the heat mostfed the bed I can not stand the bed 7A consuming

What is the bed temp being reported in Pronterface?

As waitaki says, check the temp the bed is reporting. Sprinter will not turn the heatbed on if the thermistor isn't connected. The bed, unheated, should be the same temp as the room it's in. Note that the thermistor doesn't really work for temps below about 7 Deg Celsius (real temp varies a bit), so you want to make sure it's not too cold.

If the thermistor works, check the voltage on both sides of F2 compared to Ground.

If it's 12V on one side, and less than 10V on the other side, then your fuse is tripping as the heat bed is drawing too much current.

A Mk2A bed consumes between 10-12A, depending on various tolerances. The PTC Polyfuse F2 has a rating of 11A.

I personally hate the PTC Polyfuses (they're annoying, useless and dangerous - I've seen them catch fire), so I replace them with wire links on the RAMPS board and put proper fuses in-line with the PSU.

PS: I always recommend you put fuses between the PSU and your electronics, especially if you bypass the existing protections on the board. EVEN FOR A TEST. A fuse is only a few cents, but your electronics and PSU are worth a lot more (as is your life).

the temperature is approximately the same as the thermistor detects hotend, and room temperature.

The ramps does not output to the bed, but the arduino if you send the signal to the ramp, you arrive at mostfet 5v but does not output

I get no power out of D8. I can hook my board heat direct to the 12v and it works, so it is not the board. I have a 100k thermistor connected and read 20 degrees.

Perhaps a bad mosfet?

programming?

Have you got power connected to both 12v inputs?

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Waitaki 3D Printer

i have the same problem my heat bed works directly to 12Volt sensor detects room tempature, and when i measure on the output of the bed i measure 12V on both sides the bed always work untill now what can be the problem?

hope to get it fixed :/