Spring 2020 Build-A-Block Force Sensor Tradeoff Study

Force sensor minimum requirements:

• Weight: < 5 grams

The weight must be less than 5 grams in order to avoid straining the arm, as the force sensor will be attached to the claw at the end of the arm. Torque calculations have been done for the weight of the arm in the Servo and Torque blog post.

• Range: 0 mm to 50 mm

The range of 0 mm to 50 mm is because we are attaching the sensor to the claw of the arm, which will be located close to the Jenga Blocks. In order to properly sense the blocks the range must be small enough to allow the user to adjust accordingly when within a close enough range.

• Voltage: 3.3 V

The force sensor will be powered by the 3DoT which requires a 3.3 V source limit.

• Dimensions: < 20mm x 20mm x 20mm

The force sensor will be placed on the claw, so a dimension limit of 20mm x 20mm x 20mm would allow the claw to operate properly without the sensor getting in the way.

TYPE	GENERAL INFO	SPECIFICS	PRICE	REQUIREMENTS
Time of Flight (TOF)	Use for range finding, emits light. Small and low weight. Uses timed pulses with very little delay time. Generally used for larger ranges (meters).	Weight: 11 g Operating range: 0.1m-12m Supply Voltage: 5V +/- 0.5V Dimension:35×18.5x21mm Average current: <= 110mA Power: 550mW	$44.95	✗ WEIGHT ✗ RANGE ✗ VOLTAGE ✓ DIMENSIONS
Infrared (IR) Sensor	Emits or detects infrared radiation to measure distance. Often used for motion detection.	Range: 40 mm – 300 mm Voltage: 4.5V – 5.5V Dimensions:29.5x13x13.5mm Current: =~ 3mA Power: 13.5mW	$13.95	✗ WEIGHT ✗ RANGE ✗ VOLTAGE ✗  DIMENSIONS
Force Sensitive Resistor	Changes its resistance when a force/ pressure is applied. Allows users to detect physical pressure, squeezing, and weight.	Weight range: 100g – 10kg Dimensions:60.33×19.05×12.7mm Resistance: 4kOhm @ 200 g, 1MOhm at starting	$6.95	✗ WEIGHT ✗ RANGE ✗  VOLTAGE ✗  DIMENSIONS
Hall Effect Sensor	Metal strip with current applied, when near a magnetic field the electrons deflect to one side. Can be used for proximity sensing (most helpful), positioning, and speed detection.	Voltage: 3.5V – 24V Current: <= 5mA Power: 17.5mW	$0.95	✗ WEIGHT ✗ RANGE ✗ VOLTAGE ✓ DIMENSIONS
Load Cell/ Sensor	Transducer that converts force (tension, compression, pressure, or torque) into a directly proportional electrical signal. The electrical signal can be measured.	Voltage: 6V Dimensions:47x12x6mm Capacity: 100-1500 g	$9.95	✗ WEIGHT ✗ RANGE ✗  VOLTAGE ✗  DIMENSIONS
Photo Interrupter	Sensor that emits infrared from one side to another that can detect when an object passes between.	Gap range: 10mm Voltage: 6V Dimensions:18.6×15.2x5mm Current: 50mA Power: 75mW	$2.50	✗ WEIGHT ✗ RANGE ✗  VOLTAGE ✓ DIMENSIONS
Proximity Sensor(Adafruit)	Add basic gesture sensing, RGB color sensing, proximity sensing, or ambient light sensing. Detects simple gestures , returns the amount of red, blue, green, and clear light, or returns how close an object is to the front of the sensor. Uses an I2C	Product Weight: 1.3g / 0.0oz Voltage: 3.3 V – 5.0 V Dimensions:17.8mmx17.8mmx3.2mm Current: < 100 mA	$7.50	✓ WEIGHT ✗ RANGE ✓ VOLTAGE ✓ DIMENSIONS
Ultrasonic Distance Sensor – HC-SR04	Provides 2cm to 400cm of non-contact measurement functionality with a ranging accuracy that can reach up to 3mm	Ranging Distance: 2cm – 4m Operating Voltage: 5V DC Dimensions: 45x20x15mm Operating Current: 15mA Measure Angle: 15°	$3.95	✗ WEIGHT ✓ RANGE ✗ VOLTAGE ✗ DIMENSIONS
VCNL4040 Proximity and Lux Sensor	Proximity sensor that works from 0 to 200mm and light sensor with range of 0.0125 to 6553 lux	Weight: 1.7g / 0.1oz Voltage: 3.3 V – 5.0 V Dimensions:25.3mmx17.8mmx4.6mm Current: < 100 mA	$5.95	✓ WEIGHT ✗ RANGE ✓ VOLTAGE ✗ DIMENSIONS