I have constructed a new printer Ramps 1.4. and testing.
Now have now connected the heat-bed and hot end heaters.
When I power the printer on, the heatbed heater turns on.
There seems no control.  I have connected Ponterface.  I can`t have it shut even via the M code.
The diode connected with the heatbed heater is solid on and does not flicker.  Is this a firmware issue or something to do with my ramps board?


  • its the mossfet which is propably damaged....
  • Not the first mosfet doing this, also with wrong pin numbers setting the pin this can also happen, but with right board it is unlikely if you did not use manual pin numbers.
  • HI,
    Just changed the mossfet and it still does the same thing.  As soon as I switch on, the heatbed would start heatiing...
    what are the pins you mentioned, so that I can have a look at this as well please?
  • Ramps mosfet pins are 8,9 and 10. 9 is also used by fans so that can be a problem but bed has no double assignment in pins.h so if you did not assign it a function it should be ni problem. Also uploading a simple blink script might help analyse the problem, modify it to use the mosfet pin and you see if mosfet works or not.
  • Please can you let me know how to do this?  is this a command through pronterface?   I am not so smart yet in this Jargon.  Thanks
  • No arduino ide has sample scripts you can upload. One is a blink script to turn a pin on and off with a frequency. Normally pin 13. modifying this to a pin to test should show if mosfet works, e.g. with 5000ms wait you can easily measure if voltage changes or not. Ans since it has no other prins in use there is possibility for otherfunctions misusing a pin,
  • Sorted this but I cannot understand really how it came about.  I used the online configuration tool which set my configuration.h file  with the details under Heat configuration to read...
    #define HAVE_HEATED_BED 0
    changed this zero to 1 and it works fine.  My difficulty to understand how the configuration tool turned this to read as such..

  • Normally happens if you change the file manually afterwards. It will then not see your changes as the set values are stored at the end of the fileand this data is used when you reupload it.
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