A gas and smoke sensor lets a robot notice dangerous or important changes in the air. In inspection, safety, and environmental robots, this helps detect leaks, fire risk, pollution, or poor ventilation before people enter the area. The sensor turns chemical or particle information into an electrical signal that a microcontroller can read.
This makes the robot able to respond by stopping, sending an alert, turning on a fan, or moving toward a source.
Key Facts
- Many gas sensors change resistance when target gas molecules react at the sensing surface.
- Ohm's law for a sensor circuit is V = IR.
- A voltage divider output can be estimated by Vout = Vin × R2 / (R1 + R2).
- Smoke sensors often detect particles by measuring how they scatter or block light.
- Analog sensor output is usually read by an ADC, which converts voltage into a digital number.
- Sensor calibration compares output to known gas concentrations, often measured in ppm.
Vocabulary
- Gas sensor
- A device that changes its electrical output when certain gas molecules are present.
- Smoke sensor
- A device that detects tiny airborne particles produced by burning or smoldering materials.
- Parts per million
- Parts per million, or ppm, is a concentration unit meaning how many parts of a substance occur in one million parts of air.
- Analog-to-digital converter
- An analog-to-digital converter is a circuit that changes a voltage signal into a number a computer can process.
- Calibration
- Calibration is the process of matching sensor readings to known reference values so measurements are meaningful.
Common Mistakes to Avoid
- Assuming one gas sensor detects every gas. Most sensors are more sensitive to certain gases than others, so the sensor type must match the target hazard.
- Ignoring warm-up time. Many metal-oxide gas sensors need time to heat and stabilize before their readings are reliable.
- Treating raw voltage as exact concentration. A voltage reading must be calibrated and may be affected by temperature, humidity, and airflow.
- Placing the sensor anywhere on the robot. The sensor should be exposed to moving air and kept away from heat, dust buildup, and the robot's own exhaust or battery fumes.
Practice Questions
- 1 A gas sensor is in a voltage divider with Vin = 5.0 V, R1 = 10 kΩ, and sensor resistance R2 = 15 kΩ. What is Vout?
- 2 A robot ADC has a 0 to 5.0 V range and 10-bit resolution, giving values from 0 to 1023. If the sensor output is 2.5 V, what ADC value is expected?
- 3 A safety robot detects a rising gas reading while moving down a hallway, but the fan in the hallway is blowing air toward the robot. Explain why the strongest reading may not be at the actual leak location.