Quantity   Component name
1 × ESP32 ESP32 board of any type
1 × 4-channel relay board https://www.amazon.com/ELEGOO-Channel-Optocoupler-Arduino-Raspberry/dp/B01HEQF5HU/ref=asc_df_B01HEQF5HU/?tag=hyprod-20&linkCode=df0&hvadid=198076677096&hvpos=&hvnetw=g&hvrand=8762145609143418139&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9012218&hvtargid=pla-350609711896&psc=1
1 × 4-pin trailer connector https://www.amazon.com/CURT-58381-4-Way-Connector-Socket/dp/B001GN6TXC
1 × 5-volt USB battery Any 5-volt USB battery that can power the ESP32
1 × 12-volt battery Any small 12-volt battery that can power the trailer lights
1 × Connectors Connectors that can be used to attached the 12-volt battery to the relay board
1 × Female-to-female jumpers https://www.amazon.com/GenBasic-Piece-Female-Jumper-Wires/dp/B077NH83CJ/ref=asc_df_B077NH83CJ/?tag=hyprod-20&linkCode=df0&hvadid=309750549985&hvpos=&hvnetw=g&hvrand=341341612727956879&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9012218&hvtargid=pla-567322001486&psc=1
1 × Wires Wires, as needed