Version 1

6/2023-9/2023

INTRO

In this project I wanted to focus a little more on boost converters on a PCB and 7 segment displays. The board has 3 buttons, two for raising the score on the respective display and a reset button. The board has a boost converter paired with a 5v regulator to convert the raw voltage from a Li-Po battery into a linear 5v for the microcontroller. The 7 segment displays are controlled with shift registers in order to reduce the amount of pins needed to drive the 4 displays.

PCB AND SCHEMATIC

This was my first time using shift registers and designing a boost converter, I followed the datasheets carefully and was able to come up with a proper schematic. I used the MT3608 switching IC for my boost converter, which is designed specifically for boost converter circuits. The datasheet included a formula for getting the value of 2 resistors which sets the output voltage of the circuit. It also included suggested values for the capacitors and inductor which I used. The shift registers were simple, just 3 pins from the first one to the MCU, and then daisy chain the rest of them to the first one. I also threw in a small motor so I could experiment with haptic feedback when the user presses buttons on the board.

TESTING AND ASSEMBLY

This is the first version of the pocket scoreboard. After assembling this board on 5 different occasions, I noticed a few mistakes. I had set one of the pins on the shift register to GND, when it should have been set to high, hence those orange wires on the back. I also picked capacitors and inductors that were too small, and were experiencing current throttling because of their limited current ratings. I also fried the MCU I used, since I was trying to use a hot air gun in order to be able to solder pins underneath.

I am currently working on the next version, this next version will fix these small issues, along with use a different MCU that is cheaper and easier to solder in order to cut down on production costs.

Version 2

9/2023

CHANGES

In this version, I was able to successfully fix all the problems that version one had and made a more reliable board with some added features. The boost converter is now powerful enough to supply the 0.8 amps that the circuit demands. This was done by adding a larger inductor along with bigger capacitors. I also fixed the misrouted pins on the shift registers, and added resistor networks on each output of the shift register to ensure that the current restriction for each segment would be uniform and allow each segment to get the full amount of power it needed. I also added an 18650 battery holder to give the battery a proper spot on the board. Some additions include a Neopixel at the bottom of the board for battery indication or other future uses, and finally, a different MCU that can more easily be sourced and attached to the board.

ASSEMBLY AND TESTING

I’m happy to say that this version works perfectly with no bugs. The new larger displays are very bright and make it easier to see from a distance. The only thing I would say that I wasn’t anticipating was the high current consumption from these new displays. With a current draw of 0.70-0.85 amps, the battery will be able to power this board for around 3-4 hours, which is plenty of time for a few games. Overall I learned a lot from this project and have solidified my knowledge on buck converters and shift registers quite well. If you have made it this far, thank you so much for reading about my journey on this project.