I decided to start building my Maslow with the electronics. One of the goals I had for my machine was to have an enclosure for the arduino and motor controller.
I have a couple simple goals with this PLC case:
- To protect the electronics from collision and dust
- To provide more cooling for the motor shield
- As many components as possible need to be from my bin of discarded electronics.
- To make it easy enough to modify and remove parts as needed.
Number 1 is fairly easy. First, I need a shell that fits around the electronics. I have an XYZ DaVinci 1.0 3D printer with the ability to print ABS, so the easiest thing to do is to model up the case real quick, and then print out a prototype to see how it works. Yes, part of my choice to use the printer is novelty
Which brings me to Number 2, cooling the motor controllers. From what I’ve read, the motor controllers generate a lot of heat. If I’m putting this in an enclosure, it’s going to need airflow or I’m going to fry my electronics. My thought is to use a computer case fan with an air filter on the intake side to provide airflow through the case. This is what really determines the design, since I will have to design the case around the fan.
And this takes us to number 3. I have a bin full of useless (but not broken!) electronics from old computers. Among my collection are a number of 80mm and 120mm case fans. Looking at the motor controller, 120mm would simply dwarf the PLC. Also, such as case would probably exceed the printer’s bounding box. So 80mm it is! Plus, with such a standard size fan it will be very easy to source a fan filter that mounts right to it.
Number 4 is especially important to me because I build/repair and fly multicopters as a hobby. These can be notoriously difficult to work on in their cramped frames. For instance, my current quadcopter requires removing 20 screws to get at it’s motor controllers, and takes considerable time to take apart.
So after a couple of evenings of work, I had a working prototype:
I wanted to relocate all of the board’s ports to the outside of the case. That when the door is closed, I can still swap cables without too much trouble. I also read in the old forums that it was easy to get mixed up as to which DC in port to use. I’m pretty absent-minded, so I made it idiot-proof and covered the arduino port so I can’t plug it in wrong. The more difficult task was to make the extensions for the motor controllers, but after some research I found that they are the same type of connector as those used on 5-cell RC place lipo batteries. Looks like my dabbling in multicopters is paying off
So then I printed it:
Now, my printer is nothing special. It’s technically pretty old by printer standards. The slicer (G-code generating software) is very limited in it’s abilities and as such I have very little control over the support structures and such.
I spent tonight cleaning it up:
And then installed the electronics
With the arduino and motor controller, I really wanted to be able to easily remove the whole unit at once. I attached nylon standoffs to the bottom of the arduino, so that way all I would have to to is screw in those standoffs.
Here’s the motor controller right after I installed it in the case. The eagle eyed among you might be able to notice that the front standoffs don’t have nuts on them. They wouldn’t fit next to all the pins on the arduino! I put those standoffs in and tightened everything else down. They won’t be securing the board, but at least they’ll keep it spaced off the base.
I tested the fit of the power and USB cables next. It took a little shaving on the power port. The hole ovaled quite a bit during printing (did I mention my printer is nothing exceptional?).
So next I attached the fan and motor port extenders. To install the fan, I actually needed to take the boards out first! Didn’t think that part through >.>
For the extenders, I simply bought a packet of the balance ports. I soldered the female connector to the ends at the right length. Then everything plugs right in.
The female ports were secured using some epoxy. I’m not sure how tough these are right now, and I may ultimately need to make a catch plate or something to hold it in place.
I have not printed the door yet, so that will have to wait for now. To be honest, I may leave it off for the moment while I get everything set up. We’ll see how I feel!