Trade Off Study – IR Line Sensor
Fall 2017 | Sojourner Team | By Zach Oyog (E&C Engineer) | 10/20/17
Introduction
The line sensor will need to accurately detect lines from a distance of 3.5 centimeters, the distance from the bottom of the rover chassis to the 2D maze[1]. The maze consists of a white background with dark/black grid lines and green lines that intersect the grid lines [2]. The green lines have been designated as walls, which the rover must avoid. The current design of the rover utilizes IR line sensors in conjunction with RGB color sensors for detecting path lines and wall lines. The IR line sensors must be able to detect the dark grid lines to keep the rover on track when making turns and going through the intersections of the maze.
Infrared Line Sensor Specifications
Our team considered these options for IR and color sensors:
QRE1113 (Digital) [3]
- 5V DC operating voltage
- 25mA supply current
- Digital I/O
- Optimal sensing distance 3mm
- Price: $2.95USD
QRE1113 (Analog) [4]
- 5V DC operating voltage
- 25mA supply current
- Analog I/O
- Optimal sensing distance 3mm
- Price: $2.95USD
QTR-1RC Reflectance Sensor [5]
- 5VDC operating voltage
- 17mA supply current
- Digital I/O
- Optimal Sensing distance: 3mm
- Maximum recommended sensing distance: 9.5mm
- Price: $4.95USD
QTR-1A Reflectance Sensor [6]
- 5VDC operating voltage
- 17mA supply current
- Analog I/O
- Optimal Sensing distance: 3mm
- Maximum recommended sensing distance: 6mm
- Price: $4.95USD
Analysis
According to the retailer’s specifications, the IR line sensor’s optimal and recommended sensing distances are not great enough to cover the 35mm distance needed. If the sensing distance was sufficient, the QTR-1RC would have been the ideal choice of an IR sensor due to its digital I/O and lower supply current at 17mA.
Conclusion
Further research will be needed to find a sensor that can meet the sensing distance, or an addition to the chassis will be needed to decrease the distance. If neither of these options are feasible, the electronics and control engineer will need to find a new method of line detection for the maze.