Horn Board

Overview:

This project designs a horn board for a car, utilizing the esp32 microcontroller to output sounds through a physical speaker. It needs to be able to switch between two power sources (CAN and AUX), prioritizing the AUX power but having the option to manually decide.

Features:

• Compute:

  • Esp32 wroom 1 microcontroller (utilizing the OTA feature)

  • Stores audio files

• Power:

  • Buck converter (convert the 18v/ 12v/5v to 3.3v

• Actuation:

  • Speaker (DAC and Amplifier IC) 

  • LEDs (mainly for debugging, turns on when specific parts of the board works)

Schematic

Layout

BOM: total cost is $74

Issues:

• Layout wise ( underestimated the details)

  • Can connector, transceiver, and diode needs to be close to esp32 (top right would be good) for better signal integrity

  • Check track widths (made track widths for power thicker but didn’t consider actual calculations)

  • Used wrong footprint for buck converter (hence the hot glue) and some other parts

  • Did not need UART (esp32 has the functionality)

  • Mechanical constraint (considering how it actually fits in the car)

  • TVS Diode is super tiny! (probably use actual zener diodes as replacement to make it easier to solder)

• Schematic wise

  • Enable pin is always in run mode (connected to power)

    • Needs to connect to ground in order to flash code (should have added a switch)

  • Master clock has to connect to GPIO0 to get data from esp32 to DAC)

  • Pins from data line for esp32 are connected to the amplifier IC (currently we have resistors shorting them so that connection is gone —> once OTA works, can unshort)

  • Specifying which side is on/off for switch

  • boot/reset buttons (boot helps flash firmware, reset -> turn it on/off)

  • Keepout zone for esp32 has to be off the board for better signal

Things that do work:

• Esp32 does get power from the USB-C (data lines working)

  • Buck converter works (converts 5v from laptop to 3.3v for esp32)

  • Green LED lights up to indicate that

• 18V battery does power the board and all wires connected to it gives power to the appropriate components

  • LED lights also light up to indicate that

• Physical switches work! (toggling it turns power off/on)

• Speaker?? → amplifier works when given a frequency

• CAN?? TBD

Next steps:

• If we want esp32 on our current board to actually work, need to cut off connection from enable pin and power pin (currently shorted)

• Speaker??? → need to correct esp32 to give signal to DAC → Amplifier -> speaker

Learnings:

• To not underestimate the importance of layout

  • It’s much more than just connecting wires

  • Spend more time on layout (placement matters)

  • Shorter wire connections

• Double check pin connections to esp32

• Order at least 2 of each parts (we only ordered one of each and had issues and delays)

• Speaker?? (works but need to test it with our actual board and signal from esp32)

Bringup: