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Topic: Controlling external fan?
splitbrain
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Controlling external fan?
on: March 18, 2012, 09:33

I'm currently trying to learn how to use Slic3r instead of Skeinforge and noticed that it contains "Cooling" options to control a fan to cool printed parts.


Now I'm wondering if the Huxley electronics do support this and if so, how to connect the fan wires. Any hints?
scropp
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scropp
Re: Controlling external fan?
on: March 20, 2012, 16:01

I am guessing you have the sanguinololu electronics because if you had the melzi the answer is printed on the board.
splitbrain
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Re: Controlling external fan?
on: March 21, 2012, 07:53

Oh right, I guess I should have mentioned this. Yes, it's the sanguinololu.
smartroad
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Re: Controlling external fan?
on: March 21, 2012, 08:06

I think you would have to make a small transistor switching circuit and run it off of a spare IO pin. Then the firmware would need to be updated to respond to the G code.


All in all it shouldn't be too hard.

Based in Hampshire. Read my wiki page: http://www.emakershop.com/wiki/smartroad
Alzibiff
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Alzibiff
Re: Controlling external fan?
on: March 21, 2012, 11:45

In the configuration.h file for the Melzi, there is a line which suggests, (to me), that the fan is already set up by the line:

#define FAN_PIN 4

and looking at the schematic, I am assuming (again) that the '4' refers to port B, I/O number 4 of the ATMEGA 644P which will come into play elsewhere in the firmware. That is, to connect an external fan to the Melzi, it is just a case of wiring it to the two connectors and letting Slic3r do the switching on and off according to the user settings – does this make sense?


In the Sanguinololu configuration.h file there is something similar:

#define FAN_PIN 12 // MOSFET output marked Bed on Sanguinololu 1.3a

again – does this not say that there is already a switching transistor/MOSFET already wired in?


Please set me right if I have totally misunderstood all of this – don't want to go connecting things where things should not be connected!

Alan
smartroad
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Re: Controlling external fan?
on: March 21, 2012, 12:08

Looking at the current Configuration.h on Github there is the option FAN_PIN which is set to -1 (i.e. no pin for it). The Sang board has pins 10-12, 16 and 17 available. So once a switching circuit is made, it can plug into one of those pins and then change the FAN_PIN to reflect which pin it is on.

Based in Hampshire. Read my wiki page: http://www.emakershop.com/wiki/smartroad
smartroad
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Re: Controlling external fan?
on: March 21, 2012, 12:15

@Alzibiff


You are correct that the Sang board does not have a circuit to switch on the fan. If you were to connect the fan to a spare pin it would most likely blow the ATMEGA chip (at best the it simply wouldn't work).


If you are comfortable reading circuit diagrams (no offence if you are, I don't know your knowledge/skill ;) ) then have a look at the section of the Sang that controls the nozzle and heated bed for something that would work for the fan.


I've been thinking of adding this myself (pulled a 130mm fan out of a blown PC PSU :D ) so may well look at the options and circuit needed.

Based in Hampshire. Read my wiki page: http://www.emakershop.com/wiki/smartroad
Alzibiff
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Alzibiff
Re: Controlling external fan?
on: March 21, 2012, 12:27

@Smartroad

I don't think that I made myself as clear as I should have done as I was suggesting that adding an external fan to BOTH Melzi AND Sanguinololu should be a simple and straightforward exercise given that both boards appear – to me – to have both pins available which are marked for this purpose AND suitable MOSFETs to drive them.

Just taken a look at the Github and found this on line 285 of the Sanuinololu configuration.h file:

#define FAN_PIN 12 // MOSFET output marked Bed on Sanguinololu 1.3a

(https://github.com/reprappro/Firmware/blob/master/Sprinter_Sanguinololu/Configuration.h)

and looking at the Sanguinololu picture (step 4 on this page: http://reprap.org/wiki/RepRapPro_Huxley_Sanguinololu_wiring just above the connector marked EH). there IS a spare MOSFET which is adjacent to the 'Bed' pins which are marked as +12v and -V

As said, until I get a "yes, I've done that" from someone I am VERY reluctant to try it out! (Yes – lacking confidence). If you still think I have misread things, please let me know – genuinely trying to get to grips!

Alan
smartroad
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Re: Controlling external fan?
on: March 21, 2012, 14:16

Looking at the Sang board on the RepRap Wiki (at work so can't look at the eagle files for 1.3) pin 12 is the pin for the bed heater mosfet. I am confused by that config from reprappro's github, the one on eMakers github has FAN_PIN set to -1, i.e. nothing connected.


Another thing that confuses me on the RepRapPros config is:

#define HEATER_1_PIN 10 //12 // (bed) – marked D10 on Sanguinololu 1.3a expansion header


The heater_1_pin should be for the bed heater. So currently it is set to pin 10 (which is on the expansion header and wouldn't work, if this was burnt to the Sang then when the system told it to turn on the bed nothing would happen as nothing is connected. The rest of the line doesn't make sense either; could it be suggesting that you need to change it to 12 if you have the Sang?


Have a look at:

https://github.com/emaker/Sprinter/blob/master/Sprinter/Configuration.h


this is the firmware that I have on my machine. I wonder if the RepRapPro one is targetted towards thier electronics rather then the Sang used on the beta ones…

Based in Hampshire. Read my wiki page: http://www.emakershop.com/wiki/smartroad
reprappro
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Re: Controlling external fan?
on: March 21, 2012, 14:29

The Sanguinololu has two MOSFETS on board. Ordinarily these are intended for the nozzle and bed heaters. With the PCB heatbed, there is a bed mounted mosfet, so with this configuration (bed driven from D10), the Sanguinololu bed MOSFET (D12) becomes redundant and may be used to power a fan.


On the Melzi boards, there are three MOSFETs, so enough for nozzle, bed and fan.
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