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Microcontroller-Free Obstacle-Avoiding Robot

A microcontroller-free obstacle-avoiding robot built from IR sensors, op-amp comparators and discrete transistor (RTL) logic gates driving an L298N H-bridge — CSE350.

Watch the story
Microcontroller-free obstacle-avoiding robot
Visual story

Circuit controls the robot

Scroll to watch it unfold. Each beat is one documented step of the project.

  1. 01

    Infrared sensing

    Infrared light bounces back off the obstacle.

  2. 02

    Comparator

    An op-amp comparator turns the reflection into a clean on/off signal.

  3. 03

    RTL logic

    Resistor-transistor logic gates built from NPN transistors decide the response.

  4. 04

    Motor driver

    The L298N H-bridge changes the motors so the robot steers away.

  5. 05

    Outcome

    The robot turns away with no microcontroller and no code.

  6. 06

    Clear path

    With nothing ahead, both motors keep driving forward.

An illustration of how the system works, drawn from the write-up below. It is not recorded output.

Overview

An obstacle-avoiding robot that navigates with no microcontroller and no code at all — every decision is made by discrete electronics. It's a hands-on demonstration that autonomous behaviour doesn't always need a programmable brain, built for CSE350 (digital logic / electronics).

How it works

Infrared sensors paired with op-amp comparators turn how much light bounces back off an obstacle into clean binary (on/off) signals. Those pass through Resistor-Transistor Logic (RTL) NOT gates built from NPN transistors, which generate the motor-control logic, and an L298N H-bridge then drives the two DC motors. The result: the robot steers away from obstacles purely through analog sensing and transistor logic.

Why it's interesting

By removing every programmable component, it becomes a clear teaching model for beginners in robotics and digital electronics — and a reminder of how much you can do with comparators and a handful of logic gates. Bench testing showed reliable detection and dynamic response across a range of obstacle scenarios.

By the numbers

0Microcontrollers / lines of code
2 IRSensors → transistor logic → motors

Schematic & figures

Full circuit: IR sensors → op-amp comparators → RTL NOT gates (NPN BJTs) → L298N H-bridge → DC motors — no programmable parts.
Full circuit: IR sensors → op-amp comparators → RTL NOT gates (NPN BJTs) → L298N H-bridge → DC motors — no programmable parts.

Tech stack & key skills

Core tools, methods and skills demonstrated in this project:

Digital electronicsResistor-Transistor Logic (RTL)BJT / NPN transistorsOp-amp comparatorsIR sensingL298N motor driverCircuit designBreadboarding
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