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Bed Fan only on at 100%

Posted by scubi

scubi

Bed Fan only on at 100%
October 19, 2017 07:50AM

Registered: 10 years ago
Posts: 154

Hi Guys
I have added bed fan to my Prusa style printer. My print starts and on the second layer the bed fan comes on, but if I try turn it down to arounf 90% or 80% the fan stops ?
Using Marlin firmware, Ramps 1.4 etc

Why is my fan only capable of working at 100%

Thanks

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MechaBits

Re: Bed Fan only on at 100%
October 19, 2017 04:15PM

Registered: 7 years ago
Posts: 1,671

Where's it plugged in?

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Dust

Re: Bed Fan only on at 100%
October 19, 2017 04:36PM

Admin
Registered: 12 years ago
Posts: 6,786

Some fans you just cant PWM... some have managed to solve it by putting a small capacitor across the wires

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scubi

Re: Bed Fan only on at 100%
October 20, 2017 06:56AM

Registered: 10 years ago
Posts: 154

Hi
I have the Fan plugged into the Ramps Board where the heated bed fan usually is.
I need to try another fan and see if does the same thing.

Just strange that when I try reduce power , it switches off . Runs only if its at 100 %.

Thanks anyway for your time & replies.

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dc42

Re: Bed Fan only on at 100%
October 20, 2017 07:01AM

Registered: 9 years ago
Posts: 14,646

Quote
scubi
Just strange that when I try reduce power , it switches off . Runs only if its at 100 %.

That's typical of fans that don't like PWM. Sometimes you can get them to work by reducing the PWM frequency to 100Hz or even lower.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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scubi

Re: Bed Fan only on at 100%
October 20, 2017 07:20AM

Registered: 10 years ago
Posts: 154

Hi
Thanks, stupid question , how do I reduce the Hz ? Where is this setting, is it in Marlin Firmware ?

Thanks

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dc42

Re: Bed Fan only on at 100%
October 20, 2017 10:33AM

Registered: 9 years ago
Posts: 14,646

I don't know Marlin well so I'll let someone else answer that. In RepRapFirmware you change the PWM frequency using use a M106 command with F (frequency) parameter in the config.g file on the SD card.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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MechaBits

Re: Bed Fan only on at 100%
October 20, 2017 02:12PM

Registered: 7 years ago
Posts: 1,671

Does it matter if Marlin is set on something other than EFB or whatever for the board?
There seem to be a few similar.(from memory)

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scubi

Re: Bed Fan only on at 100%
October 24, 2017 07:24AM

Registered: 10 years ago
Posts: 154

Hi
Thanks guys for the help. Sorted out by changing the fan. It works fine now.

Thanks