OpenAstroTracker Minimal Controller Enclosure for Mega 2560 and Ramps 1.6

This is my custom enclosure for the OpenAstroTracker open-source motorized sky tracker for DSLR cameras. Details for this project can be found here:

https://wiki.openastrotech.com/

I was looking for a compact enclosure for the minimalist controller build. No screen, GPS, leveling sensor, etc. Just the motor controller. Since I couldn't find something I liked, I made my own, including modeling all of the utilized components to ensure they fit in the enclosure. It's a little snug, but they all fit with a little room to spare.

The box is designed to be screwed down to a platform for stability.

Models include a fully-detailed version with all major components included. This model is quite large. Separate models of just the enclosure and lid are also included in STEP and STL formats.

Lastly, note that I already had much of this hardware laying around as spares after completing other projects. If buying everything from scratch, it can become quite expensive to build. I've tried to provide links to most of the hardware and electronics used in this build. If there are questions on sourcing components or the assembly process, just leave a comment and I'll try to help.

How I Designed This

Design Info:

This model was designed using Fusion 360 and a lot of hand-measuring with calipers. Initially, I looked for models of the Ramps 1.4/1.6 and Mega 2560 boards, but I found some with mounting holes in different positions compared to my own boards, so I took to just modeling up exactly what I have.

Note that this design utilizes the Zyltech Ramps 1.6 board design and the Elegoo Mega 2560 board design.

I also found models for the stepper drivers, XT60 connector, Noctua fan, and other items.

Hardware:

This is a list of the hardware used, including electronic components:

• Elegoo Mega 2560 microcontroller (Amazon link)
• Zyltech Ramps 1.6 shield (Zyltech link)
• Noctua 40mm x 10mm fan (Amazon link)
• XT60 female panel-mount power connector (Amazon link)
• BigTreeTech TMC2209 stepper drivers (Only need 2 if you're not using the AutoPA base, or 4 if you are using the AutoPA base. The model shows 5 just to ensure they'll fit.) (Amazon link)
• USB B to USB C adapter (Amazon link)
• 6x M3 x 8mm brass threaded inserts to mount the boards
• 3x M3 x 8mm socket head screws to mount the Mega 2560 (one hole is too close to other components to use)
• 2x M3 x 20mm socket head screws to snug down the Ramps 1.6 board onto the Mega 2560
• 4x M4 x 6mm brass threaded inserts to attach the lid
• 4x M4 x 10mm countersunk head screws for the lid
• 4x M4 x 16mm or M4 x 20mm screws and nuts to attach the fan
• 2x M2.5 x 8mm screws to attach the XT60 panel-mount connector
• Fan cover mesh material (Amazon link)
• 5x #8 wood screws to mount the box to your platform of choice

Optional:

• Loctite thread locker to keep screws from coming loose. Probably not necessary, but good for a little extra peace-of-mind.
• 2-pin JST plug and socket to power the fan

Links to threaded hardware:

• Amazon link to variety pack of socket head screws
• Amazon link for a variety pack of threaded inserts
• Amazon link to M4 x 10mm countersunk screws

Note: You can likely find hardware locally and save some money on small quantities, especially if you live in a country utilizing metric measurements. But, metric hardware in the US can get expensive in a hurry. Even though you don't need a bunch of metric screws, the variety packs may save money when you need a handful of screws. Big box stores usually only carry 2, 3, or 4-packs of metric screws for a couple dollars per pack. Singles of larger bolts may be a couple dollars each. If you do a lot of hobbies, it's nice to have extra metric screws for stuff, too, and they'll pair nicely with the threaded inserts.

Assembly:

First, use a soldering iron to set the brass inserts into the box. The six 3mm inserts go into the bosses on the bottom of the box. The four 4mm inserts go into the holes that attach the lid around the top of the box. Depending on your inserts, you may find that plastic gets pushed around and into the threads of your insert. Try to clear this out while it's still soft or the screws can bind up when tightening things down.

Next mount the XT60 connector with two M2.5 x 8mm screws. We'll need to remove the XT60 connector again later, so skip thread locker on those screws for now, if you're using it in this project. We need to estimate how much wire we'll need to reach the power connector on the Ramps board.

Prep your mesh grill material. If you bought 40mm fan mesh pieces, you're good on the fan side. If not, cut some to the size of the fan, then use the fan as a guide to drill the corner holes into the mesh for the screws. The opposite end of the box needs a rectangular piece approximately 25mm x 28mm. Cut a piece with scissors, then slide it into place from the top and apply a dab of cyanoacrylate (CA) glue to hold it in place, wiping off any excess along the lip of the box.

Mount your fan using the four M4 x 16mm (or 20mm) screws and nuts, with the mesh between the fan and the wall of the box.

Set the Mega 2560 board down into the box, ensuring it faces the correct way with the USB port toward the opening for the USB-C adapter. Check where the mounting holes on the Ramps 1.6 board and do not put screws there when mounting the Mega 2560 into the box. You'll find one hole doesn't have clearance for a mounting screw. Just skip that hole. Tighten the M3 x 8mm screws snugly, but not overly-tight to avoid damaging the board.

Press the Ramps board into the Mega 2560, being careful to align all of your pins before pressing it down. Once inserted, you can estimate how much wire you'll need to reach the power connector from the XT60 connector. Cut your wire to the desired length.

Remove the Ramps board and XT60 connector. It's much-easier to connect them while outside the box and then mount them together.

Solder your wires to the XT60 connector, making note of which one is positive and negative. Then strip and insert the other ends of the wire into the power connector on the Ramps board and tighten down the connector.

A couple of steps for powering the fan while the boards are apart:

• There is only one spot on the Ramps board that outputs 12V directly without needing to control any transistors. There are two holes between the main power input connector and the power output connectors for accessories or heated 3D printer beds and such. You can carefully bend the pins for a JST socket and solder it in between there. Then crimp a JST connector onto the fan wires so you can plug it into that socket. If you don't want to use a JST connector, you can solder the wires right to those holes.

Other optional steps at this point:

• You can utilize ferrules for a better connection, but this requires ferrules and a crimper which add to the cost significantly.
• You can also apply liquid vinyl "electrical tape" on the XT60 connector and any exposed wire near the power connector on the Ramps board to help insulate these exposed connections.

Once you've soldered your XT60 to the wires and connected it to the power connector on the Ramps board, press the Ramps board back into the Mega 2560. Use two M3 x 20mm screws to tighten down the ramps board to the Mega 2560, making sure the screws go through the holes on both boards and into the threaded inserts on the bottom of the box. Tighten snugly, but not overly so.

Attach the XT60 connector back in place.

Press in your stepper drivers and apply their adhesive-backed heatsinks.

Insert the USB-C adapter through the opening in the box below the ventilation on the same side as the XT60 connector. You may also find that a USB-B cable can fit through this opening and skip the adapter entirely. I wanted to use USB-C cables instead.

Wire up the rest of your project, including any UART and motor connections, as noted in the wiring instructions for the OpenAstroTracker.

Set the lid in place and screw it down using four M4 x 10mm countersunk screws.

You're done! (Whew!)

Originally published on Thingiverse by me.  Republished to Printables.