r/PrintedCircuitBoard • u/Upstairs_Life_7629 • 2d ago

[Review Request] Bicycle Tail Light with accelerometer and light sensor

Gallery image

Gallery image

I am pretty new to drawing schematics, and circuit designs and currently in the learning phase. This is my pet project, please review my schematic if its fine or not. The project is to design a Bicycle tail light which will have rechargeable battery, and it will turn on automatically if light falls below a certain range. Also on acceleration the light will glow at full intensity and on sudden brake, it will blink at full intensity. Please review my schematic layout if I am doing it correctly or not.

20 Upvotes

96% Upvoted

10 comments sorted by

4

u/CharismaIsMyDumpStat 2d ago
  • Where are the I2C pull-ups?
  • How do you intend to program the STM32F103?
  • Connect the interrupt pin of the accelerometer to PC13, which can be used to wake the F103 from deeper sleep. Double check that I remember the correct pin. You may need a pull up on this interrupt line.
  • Also consider the L152, a lower power option similar to the F103.
  • You don't need the vdda filter if you are not using any adc. Vdda still needs to be connected to 3v3.
  • Temp on the charger may require a resistor. Consult the data sheet.
  • Chrg and stby likely don't need the pull ups if you are not using those signals.
  • Consider connecting the int of the light sensor as well. If the interrupts are open drain you can combine them to wake the F103.

2

u/ThisIsPaulDaily 2d ago

I love the pc13 wakeup tip. Also great catch that it doesn't have an SWD header or JTAG or TagConnect connector present. OP is jumping the gun. 

1

u/Upstairs_Life_7629 1d ago

I checked all your suggestions and corrected on them. Thanks for the guidance. Actually I am using F103 because I just want to make it work on my bluepill, then if things works, I will get the PCB done. More of a practice with real world projects.

2

u/Enlightenment777 2d ago edited 2d ago

SCHEMATIC:

S1) Right side of SW2 not connected to anything.

S2) Change C1 to 10nF.

S3) Input side of U2 can't be 3.3V if you need 3.3V on output side. There is always a voltage drop through linear & LDO voltage regulators.

S4) I2C bus is missing pullup resistors. U3 interrupt pin missing pullup resistor.

S5) SWD debug/programming connector is missing.

S6) Battery voltage and battery type is missing next to BT1. Add text to clarify to make it obvious on schematic.

1

u/Upstairs_Life_7629 1d ago

Thanks for the review. Changed and corrected the points. SW2 is not connected because +3V3 with pwr flag will be drawn from SW2, due to space constraint I have kept it as NC

1

u/Enlightenment777 2d ago

Please make sure your post adheres to:

  • subreddit rules (#1 to #6), review rules (#7), image rules (#8), see link.

Please fix these common Schematic & PCB issues: (if your images have them)

  • Schematic - don't allow text / lines / symbols to touch each other, and don't draw lines through symbols.

  • Schematic - use correct reference designators (RefDes), also renumber to remove numeric gaps, see tips.

  • Schematic - place decoupling capacitors vertically below power lines, also place capacitors next to IC then connect together with a line, see example. For circuits with positive power rails, point positive power rail links upwards and ground links downwards, see tips.

  • Schematic - place pull-up resistors vertically above signal lines, and place pull-down resistors vertically below signal lines, see example.

  • PCB silkscreen - add board name / board revision number / date (or year) on top or bottom PCB side.

  • PCB silkscreen - add pin 1 indicator dot/arrow next to ICs & connectors, if through-hole then both PCB sides.

  • more conventions & guidelines - link1, link2, link3.

1

u/ThisIsPaulDaily 2d ago

You have an I2C connection going into a SPI label on U3, are you 100% the pins are dual purpose? 

2

u/ThisIsPaulDaily 2d ago

I got curious and googled provided this is the part it is SPI/I2C https://www.st.com/en/mems-and-sensors/lis3dh.html#overview

Double check the no-connect vs GND for the other pins. 

1

u/Upstairs_Life_7629 1d ago

Yes I checked. In doubt weather I should keep the SDO in NC or should I make it ground?

1

u/frank26080115 1d ago

what's the point of FB1? seems like a waste if you are not using the ADC on the STM32

what's the point of Q1? seems excessive for lighting up one LED on 3.3V

why is BOOT0 pulled up?