Total time: about 24 hours
Journal
Day 1 - 6/24
I mostly spent this time planning what features the control board needs. It must be able to connect to to an app, have many pins for sensors, leds, and servos, and possibly add new stuff like gyro and battery charging. I think I might use an esp32 s3 mini module.
Time Spent: 1 hour
Day 2 - 6/25
Started on the schematic for the microcontroller part. I have never really done this before so I watched some tutorials.
I added reset and boot button circuits, some caps on its 3.3v input, and a usb c connector.
Because the power is on 5v, i needed to add a voltage regulator. AMS1117-3.3 is very common, so i used it.
Time Spent: 3 hours
Day 3 - 6/26
now, I need to do the battery charging. I normally use a 2 cell lithium battery, but I'll switch to a single cell lipo because the circuit is probably simpler. Then I made the circuit by looking at a video and the datasheets of each part.
It uses a separate usbc connector for charging. has tp4056 as the carging IC, a fs312f for protection, and an mt3608 for boosting it to 5v. I also added two empty wire holes for a switch
Time Spent: 5 hours
Day 4 - 6/28
Started doing the gyro/accelerometer for the robot. The robot will need to know the direction it is facing. some options are the mpu9250 and icm 20948, but you need to do extra complex stuff to calculate its orientation. While researching these, I saw the bno055 sensor which is very accurate, but there arent very many pictures of schematics I could find for reference. I have been looking at the schematic in its datasheet and also the schematic of the Adafruit breakout board
Time Spent: 4 hours
Day 5 - 6/29
Finished the imu schematic:
All thats left is to add the connectors for sensors and servos and an led.
I added 6 3-pin connectors (one for each 5v wheel servo, one for a tiny grabber arm servo, and another for a some extra 3.3v sensor), then I added a 4-pin connector for a distance sensor and a 2-pin connector for a controllable LED.
It looks like this:
Time Spent: 2 hours
Day 6 - 6/30
The schematic is done, now I'm picking the footprints.
I decided to remove the entire charging circuit because it's too complex and is just unnecessary. I realized I usually just replace the dead battery with a charged one because I need to use it continuously.
Time Spent: 3 hours
Day 7 - 7/1
I need to make the PCB now. It must fit within a space of 45mmx67mm and should have all connectors (except for wheel and battery) inside the orange area, like shown:
I placed all of the parts on the board. All the power components are all at the bottom. The esp32 sticks out of the side. I also tried to put all of the gyro parts in the center of the board so it is more accurate. The wheel servo headers and battery connectors are on the other side. It looks like this:
I learned how to add ground planes to the pcb, so I added it to both sides.
I started the 5v power traces at the battery and made it super thick, around 1mm to 1.5mm.
Then, I did the 3.3v power traces, which goes from the regulator to the ESP module and all of the sensors. Both traces had to be routed along the side of the board because there wasnt much space.
I finally connected all of the signal pins. They had to go on both sides and needed vias. I also noticed that the ground plane got split up in many areas, so vias were needed to connect it to the other side
Time Spent: 5 hours
Day 8 - 7/2
The PCB is almost done, so I ran a design rules checker. It told me a bunch of the gnd pads werent right, so I added vias on them. Also, a bunch of wires were not connected yet, so I fixed them.
I moved all of the silkscreen stuff in better places to get rid of most of the warnings.
I learned how to add images on the silkscreen, so I added a few.
Its finished