Casper is a auto pointing telescope that uses a camera and plate solving software to find its position in the sky. Driven by two stepper motors and a custom PCB control board with a Raspberry Pi and STM32 microcontroller.
Dev Blog 4
Today I spent an hour and tweny minutes going over and checking my schematic for the PCB I am making which has a microcontroller, motor drivers and more. I checked over the schematic in a few ways, I put the schematic into claude and asked it for errors, I also manually looked through datasheets of the parts, and I researched more into the parts I was using. Here was the big things I changed.
To get code uploaded to the microcontroller I was previously using a chip to convert a USB signal into UART, which the microcontroller can read. The UART line for communication I was using was also shared by the raspberry pi, which complicated the design. To fix it I took out the USB and the USB to UART chip and decided to flash code to the microcontroller through the Pi. This simplified the PCB a lot.
I found out that the 5V to 3V3 chip I was using is kind of outdated and lacked modern features. So I swapped it to a better one and got that wired up in the schematic.
The rest of the fixes were all minor changed to other components.
Dev Blog #3
Today I spent about 2-3 hours adding 3D models and fixing footprints for the PCB control board for Casper the auto positioning telescope.
The picture attached is off all the parts on the board, but nothing is in the right spot yet.
At first I got into the flow using digikey’s database as well as Mouser Electronic’s website to find 3D models and footprints.
I figured out how to upload the footprints/models to KiCad and got most of them all in, the plan I had in the previous dev blog worked and
adding the 3D models helped with fixing a few of the footprints.
When I came back to working on it later I noticed that a bunch of my work had vanished. After a bit of investigating I found that when a 3D model
or footprint is uploaded to KiCad it locates it through the path of where the file is stored. When I had tried to organize the mess of files on my computer after downloading all the footprints/models, the paths changed so KiCad could not find them.
This meant I had to go back and redo a lot of work, this time making sure the files were stored in a more permanent place.
After that everything seems fine. Next step will be to layout and make traces for the actual PCB.
Dev Blog #2
I spend about 2 hours working on the next step in making my control board PCB. I spend the time adding footprints of all the components into KiCad.
This took a lot of time because it was a lot of searching through datasheets, digikey, and the KiCad footprint editor making sure all the components are correct.
The hardest part was trying to make sure the exact parts would fit the footprint, but I figured out a better way of going about it would be to use the 3D models provided on the part page of each component to check if the footprints are correct because I can visualy see if they will fit.
The next step for the PCB will be adding the 3D models, or at least confirming the ones in KiCad already are the right ones.
This step is not only important to confirm the footprints are correct but also for later when I design the enclosure for mounting the board to the telescope.
Hi, the project I’m working on right now is Casper. Casper is a modified 6’’ dobsonian telescope that can automatically point itself at a planet or other celestial body.
Besides a lot of research what I have done so far is make the schematic for the control board PCB. The control board includes a STM32 microcontroller, stepper motor drivers, Raspberry Pi Zero, and much more. I made it all in KiCad so the time does not log but I spent roughly 7-8 hours on making it.
How I went about making it this is I started out selecting the integrated circuits (ICs) I would use for each part of the board. I need a microcontroller, stepper motor drivers, buck converter, and a LDO. Once I knew those parts I looked at the datasheet to find the standard application circuit and followed that pretty closely, with some modifications.
Next steps are to start laying out the components for the actual board and make traces to connect them all.
