Sumo 3K - Post 04 - Electronics

This post tells the story of the BTS7960 failure, root-cause diagnosis, and the cleaner L298N redesign.

The first circuit design paired a BTS7960 43A H-Bridge motor driver with a separate step-down transformer to provide regulated 5V to the ESP32. But this didn't work as expected. The step-down transformer produced an unstable, fluctuating voltage output — sometimes exceeding the ESP32's safe operating voltage of 5V. Two ESP32 microcontrollers were destroyed by overvoltage before the cause was identified. Each failure set the project back by days.



















The symptoms were clear: the ESP32 would start up, sometimes partially function, then stop responding permanently. Initial suspicion was firmware — maybe a software crash loop. But the second ESP32 failed within minutes of first power-on with no code uploaded at all. That ruled out software and pointed directly at the power supply.


Measuring the step-down transformer output under load revealed voltage spikes significantly above the rated output. The transformer was load-sensitive; at low current draw (ESP32 at idle), it overvoltaged. The BTS7960 circuit was abandoned.


The L298N H-Bridge module was chosen as the replacement motor driver. The key advantage: it has an onboard 5V linear voltage regulator that can directly power the ESP32 from the same battery supply. This eliminated the need for a separate step-down converter entirely.


Final wiring connections


From     To         Purpose

Battery +ve         L298N 12V input Motor power

Battery –ve         L298N GND Common ground

L298N 5V out ESP32 VIN Logic power

L298N GND         ESP32 GND Common ground

ESP32 GPIO26         L298N IN1 Motor A direction 1

ESP32 GPIO27         L298N IN2 Motor A direction 2

ESP32 GPIO32         L298N IN3 Motor B direction 1

ESP32 GPIO33         L298N IN4 Motor B direction 2


The BTS7960 is theoretically a more powerful driver. But reliability is not the same as performance ceiling. In engineering, the correct component is the one that solves the actual problem reliably. The L298N's integrated regulation eliminated an entire failure point from the circuit. The final design had fewer components, fewer connections, and zero overvoltage events in all subsequent testing.

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