Hotend fan turning on/off in time with Hotbed control

Hi all,

I'm a newbie to this so upfront apologies if this a stupid question.

I've just assembled a Delta with Mega2560 and RAMPS 1.4.
I'm running Repetier firmware 0.91 and Repetier Host Mac 0.56.
Motherboard Type = 33 (which I figure is 1 extruder, 1 fan and a Hotbed)

All seems to be working well except
When I turn on the hotbed the relay activates and the hotbed begins to heat up. The Hotend fan also turns on but when the hotbed reaches temp and begins its on/off cycle to remain at temp the fan also starts turning on and off in synch with the hotbed.
All this is without turning on the hotend.
This seems wrong but I can't find a reason for it.

Am I missing something here?

Any help would be greatly appreciated.



  • Yes, seems wrong if you wired it correctly. On RAMPS fan pin is D9 and hotbed is I think D8 (the one next to power). Turning on bed switches exactly one pin and can not switch more, so if it also switches the d9 pin, I guess there might be a connection between the 2 signal lines on ramps. You could test this with a simple sketch that only switches one of the 2 outputs and see if both get switched. Or measure resistance between the two lines while unpowered.
  • Thanks. I'll take a look.

    Do you think it's possible there something wrong in the pins.h file?
    Is it worth reloading the firmware (my firmware came preloaded from the kit manufacturer).
    Or even going up to .92 version?

  • Going up to 0.92 is always a good idea. The RAMPS pins.h section is the most tested one, so that is ok. Only thing is the FAN_PIN and HEATER_2_PIN are identical, so you have to make a choice what function is should have. But as long as bed and fan are connected to different outputs they should not influence each other even with wrong pins assigned.One function always controls only one pin. So bed pin only controls pin 8. If turning pin 8 on also enables fan on pin 9 it is a hardware problem.
  • Ok thanks.
    I'll upgrade 0.92 and work from there.
    Being new to all this, can I simply upload my configuration.h file to the 0.92 firmware tool and then download the full package?
    Will I loose all my eeprom settings?
    Can I just renderer them?

    I also might go back to the manufacturer and see what they have to say about the fan/hotbed issue.

    For what it's worth. I got my first print out tonight. Just a test block. It had a lean/skew to the sides. So not completely successfully.
    But hey a print is a print! And it's my first one! Ever! How exciting!

  • Hi there.

    I've found and solved the lean problem. One of the timing pulleys had come loose.

    Now for the fan/bed problem.
    Just before I got back to the manufacturer.....again.
    I pulled the ramps board out today and on a bare board tested the resistance between output D8+ and D9+ and there appears to be direct continuity. Likewise D8- and D9- (but that's probably correct being ground).
    I'm pretty sure this isn't correct. I think this is the root of my problem.
    Just as a double check.
    But could someone please do me a favour and check a board for me. I don't have a spare.

    Very many thanks in advance.

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