Week Review 5/16/2024

This week I was hard at work on the float, we added a hard power switch on the outside and made the top of the battery pack into a PCB.

image of the Sunk Robotics Float Jena

The Power Switch

The Power Switch was a simple change that was a long time coming. Up until this point you turned Jena on by opening the tube and unplugging the power connector. Although this worked it obviously was not the most user friendly, was time consuming, and could introduce extra wear and tear on connections inside of the float.

image of blue robotics button

We ordered a Blue Robotics hard power switch which is essentially a screw that pushes a button inside of a sealed bulkhead. You can turn the screw without letting any water in, it is a component that would take us a long time to design and turn in the shop, but thankfully blue robotics sells it.

We decided to use hard power where power is cut entirely from the circuit instead of soft power where most of the circuit goes to sleep, but there is still a little bit of current flowing that keeps device on standby. Hard power reduces vampire draw, but it takes longer to start the device back up and soft power allows for faster bootups. The decision to choose hard power was because it will sit unused for long periods of time and startup time is not a concern.

Installing the power switch was fairly simple, I simply added it inline, splicing the cable then adding both a fuse to the ground line and a switch to power line. The switch is rated to handle 5 amps of throughput, which luckily is below our fuse calculations. I am using a 5 amp fuse to ensure that we do not damage the switch.

image of the fuse soldiered inline

The Battery Pack

We are using a custom battery pack to hold our AA batteries. We were using a resin print to hold battery clips and soldier wires between the clips. This worked but it added unreliability because the connects could come undone, to fix this issue we are using a PCB instead.

Making The Outline

I started by making the footprint and schematic for the battery clip component and starting to figure out how to accurately make an outline for the PCB clip. KiCad is not 3D modeling software so it does not have many of the features that traditional CAD software has. You drag and cannot accurately place components. After struggling with this for the better part of an hour, I finally realized that I should use real 3D modeling software rather than trying to do it in a PCB editor.

You can import DXF files into KiCad so I had Ben create a projection of the 3D model we used for the resin printed version, and I imported that into KiCad.

image of battery holder being imported

image of battery holder DXF in kicad

Unfortunately once it was imported we realized that the battery clips hang off of the resin version, so Ben had to model a new top and bottom where the battery clips are fully inside of the clips.

Making the Battery Clip Component

The Battery Clip did not have a component in KiCad. This was the first surface mount component that I made so far, it was fairly straightforward because it is only one big pad. We need both a strong electrical and mechanical connection so I wanted to utilize the full surface area of the back of the battery clip.

Making The Footprint

The footprint was very straightforward, I made a new component in my personal library and I made one pad. I originally made the mistake of putting the pad above the origin which caused issues when I rotated the component later, so I had to make the origin on the center of the pad. I decided not use make a silkscreen in the footprint because I have limited real estate and I want the information around the clip to be different for each one.

image of using the footprint editor

Making The Symbol

The symbol was very simple because this component only has 1 pad. I made a drawing that resembles how the battery clip looks and I added the pin.

Making the Schematic

The schematic was simple, but somewhat strange. There are two PCBs and the batteries connect them, so I just needed to connect the clips and pairs and add a connector to the top of the board.

image of the schematic

Placing Battery Clips

Placing the battery clips was a challenge and it took me roughly an hour to figure out how to do it. In this application, unlike most PCBs, freehand placing of components is not acceptable. KiCad is not well suited for this purpose, and I had never tried to make something with this level of precision before.

Thankfully KiCad has several tools for moving components, and a few of them are precise enough for this application.

  • Move - allows you to move the selected object freehand while it follows the mouse (can be accessed with the hotkey M)
  • Move Exactly - allows you to move the object to precise coordinates (can be accessed with the hotkey Shift-M)
  • Move with Reference - allows you to move the object relative to a different point than the origin of that object
  • Copy with Reference - allows you to copy the object relative to a different point than the origin of that object
  • Position Relative To Reference Item - Allows you to exactly move an object on a coordinate grid with the origin being an object of your choice (Can be accessed with hotkey Shift-P)

image of positioning tools menu

The most useful tool for this application was Position Relative To Reference Item. In the resin print there are small holes that allowed for soldiering to the battery clip. I used the position of these holes in the DXF file to move the battery clips. At first Ben and I were trying to use the absolute coordinates relative to the holes which involved some trigonometry, we then found out that it accepts polar coordinates which we decided to use. This allowed us to place the battery clips quickly and accurately.

moving with reference

Routing the board was very simple. I just needed to connect the battary clips to eachother in pairs.

New Computers

We got computers from the Toyota Research Center, Ben and I were able to use them so I wanted to see what they could do. I flashed our shop image onto them and sorted out the driver issues that come from using a premade image.

I moved my development enviroment over, I like to use WSL for this because I am much more familiar with Linux than Windows as a development enviroment.

I wanted to see what the computers could I so I installed stable diffusion onto them. I am trying to install kohya-ss onto them but I have been having trouble because it wants very specific outdated versions of everything.

Helping Metal Fab

I tried to help metal fab get their plasma cutter working. They got a Lincoln Electric plasma cutter, but all of the file formats that it can accept are not exported by TorchMate. I tried to find a solution by converting something, but it did not work. I ended up recomending that they contact support from the manufacturer, or they try using VCarve and exporting *.nc files.