Thrift-Store RC Car Conversion

01Handheld controller

02Wireless link

03Vehicle controller

04Motor stage

01 / Abstract

Abstract

Thrift stores often have radio-controlled cars without the matching transmitter. This project keeps the useful chassis and motors, replaces the proprietary electronics, and builds a new handheld controller around ESP32 hardware and ESP-NOW.

02 / Use cases

Use cases

Recover otherwise unusable thrift-store toys.
Study brushed-DC motor control, steering behavior, and wireless failsafes.
Create a repeatable conversion architecture for similar donor vehicles.

03 / Theory

Operating theory

Brushed motor control

A dual H-bridge reverses motor polarity while PWM controls average motor voltage. Driver selection depends on measured stall current, supply voltage, and thermal behavior.

Connectionless control

ESP-NOW can carry compact control packets without a Wi-Fi access point. Sequence numbers and a receiver timeout prevent stale commands from holding the motors on.

Human input conditioning

Joystick calibration, deadband, scaling, and slew limits turn noisy ADC readings into stable throttle and steering commands.

04 / Requirements

Requirements and success criteria

Measure each retained motor at the intended voltage, including brief current-limited stall tests.
Provide proportional throttle and steering with a neutral deadband.
Command neutral within 250 ms of losing valid control packets.
Complete a five-minute drive test without resets or driver overheating.

05 / Architecture

System architecture

Handheld controllerESP32, joystick, enable control, and status indication

Wireless linkSequenced ESP-NOW control packets

Vehicle controllerESP32 packet validation and failsafe state machine

Motor stageDual brushed-DC H-bridge selected from measured current

PowerSeparate motor and regulated logic rails with common reference

06 / Current status

Current status

The control architecture and safety gates are scoped. Donor-car teardown, motor characterization, steering identification, and final H-bridge selection are still pending.

07 / Next steps

Next steps

Select and document the donor vehicle.
Identify drive and steering mechanisms.
Measure operating voltage and stall current.
Bench-test the control packet and timeout behavior before connecting motors.
Select the final H-bridge from the measured load.

08 / Risks

Risks and constraints

Selecting a driver before measuring stall current can cause resets or thermal failure.
Motor noise can disturb the ESP32 without supply separation and local decoupling.
A missing packet timeout can leave the vehicle moving after link loss.

09 / Artifacts

Engineering artifacts

Planned teardown measurements
Controller and vehicle firmware
Wiring diagram and packet definition
Drive-test log and thermal observations