This is another installment in the Experimenting With Supercapacitors Design Challenge. I enjoy injecting creative design elements into any project, so while waiting for my PCB to be fabricated I thought I would address the handling issues with high energy capacitors with a little creativity. In particular I wanted to ensure the leads don't get shorted, which would degrade LiC devices that need to maintain at least a minimum charge, or high capacity devices that can deliver enough current to cause heat damage. At the same time I wanted to avoid applying stress to the capacitors such as when clamping them securely.
This blog covers 2 designs, one is a safe storage solution called the SuperCap Rack. The other one is a test stand to immobilize devices during testing without applying stress to the device under test (DUT). This multi-capacitor holder is simply called the Capacitor Test Stand.
The SuperCap Rack
The SuperCap Rack design criteria are pretty simple but there are a few of them:
- It must safely hold all the supercapacitors supplied for the challenge and it would be nice to be able to store a few more.
- It must prevent capacitor leads from shoring to each other or to any other capacitor leads, or in fact to any random metal in the area.
- It must prevent the application of stress to the capacitors
- The rack must be transportable between bench and storage location without capacitors falling out or moving enough to short out
- The capacitors must be easily accessible
- It must be easy to place capacitors in the rack
- It should not take up too much space (the case supplied is very nice and it will be put to good use, but it is too big and not well suited to these requirements
The Capacitor Test Stand
The Capacitor Test Stand design criteria were slightly different:
- It must hold each size of capacitor securely without applying stress to the DUT
- It must perform the function of a third hand without risking hands touching leads
- It must provide access to the capacitor leads for something like mini-grabber test leads
- The capacitor must be held securely enough that it doesn't skitter away when trying to connect test leads
- It must be stable enough that the weight and stiffness of test leads will not move it or tip it over
This video provides a quick view of how all these criteria were met for both the SuperCap Rack and the Capacitor Test Stand:
Discussion & Conclusions
Both devices successfully met their design criteria. I am happy to have a nice compact storage system for supercapacitors since they don't get used on every project.
Using straws to keep each lead electrically isolated was a bit tedious, but actually took a lot less time than it would take to 3D print an equivalent structure, and the price was right. I like how the SuperCap Rack turned out. It met all my criteria and is very functional. The straw idea was probably about the tenth idea that I explored when coming up with this design, and similarly the capacitor test stand concept underwent several iterations before settling on this implementation. Fortunately I find that type of exercise to be enjoyable.
The SuperCap Magic Meter PCBs finally arrived so my next video will be on assembly of the Magic Meter shield.
Following that, I will have to get some software working and then I can do some capacitor testing.