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Fan input current limits?

Posted by 3DRapidClone 
Fan input current limits?
July 11, 2014 02:29AM
Hey guys, what are the fan input current limits on the RAMPS board?
Re: Fan input current limits?
July 12, 2014 07:42PM
The fan is actually an output (not an input). The fan is usually D9, but it's possible to change the pins to rearrange the outputs, or to use D9 for something else (eg: a second extruder).

The standard RAMPS has a 5A PTC fuse that runs the Arduino Mega, the stepper motor drivers, and the D10 and D9 outputs.

The standard RAMPS has a 11A PTC fuse that runs the D8 output.

Note: Some variants of RAMPS have real fuses in place of the PTC fuses (eg: GRRF RAMPS). The max current limits will of course be different.

PS: Put some details on the wiki at [reprap.org]
Re: Fan input current limits?
July 13, 2014 12:55AM
I apologize, output. I know there is a fan header that is a non-pwm fan header next to the first stepper driver. I'm afraid to run something that is 2-3 amps on the fan output that usually has a load of .3-.5A loads from fans.
Re: Fan input current limits?
July 13, 2014 01:28AM
If you're talking about the header that is near D2 - right next to the X axis stepper driver - that is just a 12 volt header - not necessarily for a Fan. It by itself does not have a current limit, but it IS on one of the fuses - I assume the 5 Amp fuse - and so must conform to that limit in conjunction with all the other devices on that fuse.

I have two printers - on one, with just a single extruder, I am using the D9 output for the G-code controlled fan, and so I am using this header to power a fan that cools the RAMPS itself.

On my second printer, with two extruders, I am using D9 for the second extruder, so I am actually using this 12 volt header to control 2 fans: one is the always-on fan that cools the RAMPS, and one goes through a small MOSFET circuit and if G code controlled through pin D4. I have never had a problem with either printer related to running these fan.

What is it that you have that draws 2 to 3 amps?
Re: Fan input current limits?
July 13, 2014 03:45AM
Electromagnet for an automatic magnetic tool changer on my delta printer!
Re: Fan input current limits?
July 13, 2014 08:57AM
Attaching a solenoid is an entirely different matter. There you need flyback diodes. STB electronics, Gen7 and SevenSwitch have them, RAMPS and Sanguinololu not.

Generation 7 Electronics Teacup Firmware RepRap DIY
Re: Fan input current limits?
July 13, 2014 04:06PM
Thanks for the info Traumflug. I'm thinking I will use a relay hooked up to one of the free pins on the ramps with a flyback diode so I don't end up obliterating my boards.
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