Duet questions

Hello,

I've been trying to find some details about the Duet/RepRapFirmware, but so far I haven't found these details:

1. What's the amp rating for the Duet board?
2. How would I go about running multiple fans with speed controls? Would I have to get the expansion board and repurpose one of the motor outputs?
3. Has any work been done to connect an LCD for stand-alone prints? Or isn't this prioritized since it can connect it to the network instead?
4. Anything else nice that it does or doesn't support?

I'm considering a Duet for my printer, but I'd especially like to know if I need the expansion board to control multiple fans. I'm keen on multiple extruders anyway, so I may have to get the expansion board in any case.

Hi Ketil


1. The A4982 stepper motor drvers are rated to 2A but they would need active cooling to get that sort of output, they easily drive the normal RepRap printer motors as they are well heatsinked. The FETs can easily switch the >12A of the heated bed (see my blog post on thermal testing [blog.think3dprint3d.com]).
2. The Duet has one fan control on the main board but as you correctly suggest you can use the FETs on the expansion board to control further extruder heaters or fans. If you dont need the full expansion board then a simpler FET circuit could be added using the expansion header.
3. The LCD control is on the todo list but as you say you can control it through the web interface, including copying gcode files to the onboard SD card.
4. It currently supports only Cartesian printers but support for Delta, and Hbot are on the todo list (sorry its a long list) the RepRap Firmware has some nice features such as Axis compensation, support for an IR probe to measure bed height, support for Multiple extruders with colour mixing in beta. That said it doesn't have as many features as Marlin yet.

Cheers

Tony

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DuetWifi.: advanced 3d printing electronics

Thanks for the detailed answer and the link! I have a 12V 18A PSU for my heated bed. As I understand your blog post, 20A load should heat the FETs to roughly 80 degrees (provided my ambient is around 20)? Looking at other info, it also looks like the Duet can handle 12V - 24V input, so that means I can just feed it any voltage between 12V and 24V as long as the motors, heaters and fans are happy with it?

Brilliant that files can be copied onto the SD over ethernet/web. That's one of the main hassles with printing today, uploading over serial takes ages so I have to keep plugging the SD card between my computer and the controller. A 100mbit upload would be so much better.

Edited 1 time(s). Last edit at 03/20/2014 06:18PM by ketil.

Hi Ketil

No worries! As far as the heated BEd PSU is concerned that sounds fine, most "standard" heated beds only draw around 12A or so at 12V. That heating sounds about right - the normal things apply like if you are going to put it in a sealed box then ensusre you have some airflow through. The Main voltage in can be between 12V and 24V without problems, the motor drivers are current limiting so they will work fine with that range. Your heaters will obviously heat quicker with 24V and you will see quite a bit of overshoot on the hotends if you dont modify the PID values. Also at 24V a standard cartridge heater will get very hot very quickly so be careful not to have the thermistor fall out of the hotend.

Dc42 and iamburny over on the Ormerod forums added the features to improve the SD card upload and the new web interface is great!

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DuetWifi.: advanced 3d printing electronics