Saturday, June 16, 2018

UMMD: Migrating from SmoothieBoard to Duet Ethernet, Part 3

Electronics Enclosure

The Duet board and Panel Due have updated firmware, the Duet is mostly configured, it talks via a direct ethernet connection to my netbook computer, so it's time to install the Duet and Panel Due into my printer.

The cover of the printer is designed so it keeps the slots in the upper front of the machine open so I can slide the top front cover in and out of them.  That means the Panel Due has to provide the same clearance, and means I can't put switches or jacks on the front panel unless I set them back to provide clearance for that cover.

The existing electronics are screwed to the top of the printer and covered with a clear plastic basket - ugly!  I decided to mount the Panel Due standing vertically at the front of the machine and designed a mount/bezel for it, then made standoffs of equal height to support a new top cover.

I decided to use more of the 8mm thick dual layer PC for the walls of the enclosure, so I designed the standoffs with 8mm wide slots to hold the PC.

Side panels of the electronics enclosure use the same 8 mm dual layer PC as the printer enclosure.  The power switch and LCD screen are set back to protect them during transport and prevent them from scratching the upper front cover of the printer.
Once the standoffs were made, I started rearranging the electronics.  I decided to keep all the electronics on top of the machine- there's plenty of room up there, and that would minimize the number of cables running up and down the machine's frame.

The switch immediately above the main power switch is used to turn the lights on and off in the printer.  The other switch is there for future assignment.  The fan is a 120mm 220V unit that runs very quietly on 117V.  The cone in the center is there to support the center of the board (also foamed PVC) that will cover the top of the enclosure.  There are 3 fuses on the rear panel- one each for the bed and chamber heaters which are both line powered, and an extra for future expansion.
The Duet board will go where the SmoothieBoard is, minimizing additional wiring that has to be done.  I added a panel mount network extension jack to the back/side of the machine (if I put it on the front panel, I wouldn't be able to slide the top-front cover in and out of the frame with the cable plugged in).


A few weeks ago, fellow Milwaukee Makerspace member and all-around cool guy that you should know, Jim Rawson, showed me some connectors that he was going to use for making bus-type connections to power supplies for a model train layout he is working on.  The things he showed me were Wago 221 type "lever nuts".  They are intended to be substitutes for twist-on wire nuts used in electrical boxes, but they make great substitutes for screw terminal blocks.  They have nice levers that flip up to open the connector, then snap back down to make a solid electrical connection with either stranded or solid wire.  They're good for 24 to 12 gauge, solid or stranded wire and can handle at least 20A at 300V.  The only tool you need with them is a wire stripper.  These things hold on tightly- I tried pulling a wire out while the lever was down and couldn't do it.  I don't think I'll ever use screw terminal strips again.

The WAGOs are high quality German made parts with a bunch of safety certifications.  The 5 position WAGOs cost about $1 each, but you can buy no-cert Chinese knock-offs for much less, if you don't mind taking a gamble.

Wago 221-415 in a printed holder.  All you have to do is strip 11 mm of insulation off the wire, insert the end into the hole, and snap the lever down.

Yes, these things are pretty small.

After designing and printing the WAGO holders I realized that they can probably just be hot-melt glued to the baseboard of the enclosure.  I tested it and it seems to work fine.  Oh well.  To a hammer, everything looks like a nail!  If you want to print some of the WAGO mounts:

The STL file for the Wago lever nut holder is here.

The Fusion360 CAD file is here.

Power wiring diagram - most of this junk is there to enable lots of white and UV LED lighting.  The connections at A and B are for the bed heater, and connections at C and D are for the chamber heater.  There are WAGOs at A and C that I neglected to include in the diagram.  The LEDs connected at the SW GND WAGO are the white LEDs that light up the build chamber.  SWA and SWB are a single DPDT, center-off toggle switch.

I laid out the wires for the AC power first, since those are the least likely to require any changes in the future.


There were two, 24V white LED strips in the top of the enclosure, and two 12V white LED bars on either side of the front opening of the printer.  Since I had the whole top off the machine I decided to add two more of the 24V LED strips to the top cover.

The 12V white LEDs are powered by a DC-DC converter and since the 12V may be useful for other things, I decided to power that converter all the time and have a 12V source readily available for future use.  The UV LEDs are powered by another DC-DC converter that outputs about 19V to power the LEDs.  19V is not very useful for anything else, so the light switch on the front panel switches the ground on the input side of the DC-DC converter that powers the UV LEDs.


I wanted to be able to remove the entire electronics enclosure from the printer, so I thought about how to make that as easy as possible.  The connections to the controller board are all connectorized, so they're easy to deal with.  I labeled all the plugs that go into the board with their functions so it will be easy to plug them back in.  But there are a few things that will need connectors to make it easy to remove and reconnect everything.

Connections to the bed and enclosure heaters are needed, as well as connections to the LED light bars at the front of the enclosure.  Each of the heater connections involves only two wires, so I went with Anderson Power Pole connectors for those.  Since there are multiple connections needed for the LED bars, and I might want to add more lighting in the future, I decided to put some extra WAGOs in the electronics enclosure on top of the machine.  The extra connections available on the WAGOs will be useful to add fans, lighting, etc., in the future.

Top view of the printer.  I know, not too pretty...  The connections to the Duet board come up from the bottom of the enclosure to the left of the board.  In the upper left corner the connections for the bed and chamber heaters come up to WAGOs.  On the lower left the wires for the LEDs located on either side of the front of the machine come up to WAGOs.  There's a 220VAC fan in the UL corner that is powered via 117VAC, so it turns slowly and quietly.  It is positioned to blow air over the Duet board to ensure that it stays cool.  There's a vent in the UR corner to allow air flow when the top cover is in place.

24V supply and 24-12V DC-DC converter.  There are 24V, GND and 12V WAGO's to make current and future connections.

Duet board, 24V-19V DC-DC converter to run UV LEDs, 19V, 24V, 12V, and switched GND WAGOs for current and future connections.

Network connector (left), power input panel (center), bed heater SSR (orange), and line, neutral, and GND WAGOs for current and future connections.   The GND WAGO, upper right will have a connection to the printer's frame.  There is a spare fuse holder for future use, and plenty of room above the network connector to add switches, or whatever.

Next up:  Tweaking the firmware

1 comment:

  1. Thanks for the Wago holder. Very nice printer, too! :-)


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