I made our rover (PARSLEE) a clean suit and I’m really excited about it. We’re getting ready to bring it out into the desert and wanted to do what we could to keep its electronics safe. We’ll be camping on a dry lake bed, and it can be extremely dusty at times. The playa dust is very fine- I took a look under a sample under a microscope and measured the average grain size as ~80-200 microns. But the grains on the smaller end go all the way down to sub-micron size, and below the resolution of my scope. This dust gets into everything and never comes back out, and it’s very alkaline which can be hard on electronics. The dust grains are made primarily of silica and look like fluffy glass clouds (the images below are ~450 microns or ~0.45 mm across).
So I decided to try using hypoallergenic fabric to make it a “clean suit.” The fabric has a tight weave to keep out dust mites and pollen- it’s supposed to block anything <5 microns, so it’ll keep out a lot – but not all – of the dust. It turned out pretty good! It’s not really a suit so much as a rectangular bag that fits inside of the rover’s body and houses the PCB and all the electronics. There are a whole bunch of wires that feed from the rover’s driving and corner steering motors into the body to connect to the PCB. I really didn’t want to try making a port for every single wire or cable that had to be fed through the bag and measure them perfectly, so I opted instead to put a Velcro strip all the way around the outside of the bag so that cables could be fed in at any location. This also allows the bag to go over the bar that goes across the middle of the rover.
Then, since I was worried that dust would easily get through the Velcro strip itself, I decided to add a flap of fabric over the main Velcro junction with a second Velcro stripe to hold it down. This double Velcro system will also help keep out dust from the small spaces on the sides of each cable as they are fed through. We’ll see how it does, but I think it will work quite well. I accidentally skipped taking pictures of a few of the steps, but hopefully you can get the general idea of how I’m making these flaps.
Then I added a zipper around the top of the bag for easy access to the PCB when we need to plug into it. I was also worried about dust getting through the zipper, so I added a third Velcro strip/flap to protect it. This ultimately gave me two layers of entry, the zipper and velcro stripe, and two velcro layers of protection on top.
If you have any experience sewing, you can imagine it was tricky to put all the pieces together in the right order. There are also some imperfections due to minor measurement errors, but overall I think it came out well. It was a feat of engineering itself, as sewing often is!
As a final touch, I used my embroidery machine to make tiny holes the screws on the PCB could fit through so that it could go between the PCB and the rover’s back panel. I tried sewing buttons holes with a regular machine, but it was hard to make them both small and neat. We were going to add washers to make sure we had a good seal, but the holes turned out small enough to not need them.
I think it came out really nicely! It does make the body of the rover a tad crowded when you need to get your hands in there, but I think it’ll be worth it to keep the electronics safe while out in the field.