City of Philadelphia, Pennsylvania

do-it-yourself

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Wearable Assistive Tech Gripper: Doraemon's Hand is designed to assist individuals with an upper extremity amputation or with limited dexterity pick up objects. It was created by a group of students from Singapore Polytechnic.

Technical Specifications:

Skill level: Basic soldering and C++ programming skill.

Things you need:

Ultrasonic sensor SRF05
PIC18F4550
Vacuum pump from Aliexpress
Copper strip board
Copper wire
Rainbow ribbon cable
12v dc relay
NPN transistor (2N2222) for the relay
12v 2800mAH Li-Ion battery

Step 1: Building the coffee gripper. The author used a DIY coffee gripper with the vacuum pump bought from Aliexpress, hard tubing from local hardware store, balloon, and plastic bottle spout recycled from regular PET bottles. This version is extended with an ultrasonic sensor SRF05.

Step 2: Wiring with the pic18 microcontroller.

Input of micro controller: Ultrasonic sensor (2 data pins, VCC and GND)
Output of micro controller: LED bar (8 data pins), vacuum pump(1 data pin)
Port B of micro controller connect to LED bar
Port D of micro controller connect to relay & transistor circuit that is used to switched 12v dc to the vacuum pump
Connection of ultrasonic sensor can be found here http://www.robot-electronics.co.uk/htm/srf05tech.h.
Wiring of the vacuum pump requires a standard 12v DC relay + 2N2222 transistor circuit with the base connected to MCU data pin

Step 3: Ultrasonic sensor & LED bar. Construction of the sensor is as follows: tape down the ultrasonic sensor at the side of the gripper. The LED bar serves as an indicator to the distance reported by ultrasonic sensor.

Step 4: Putting everything together. Using the rainbow ribbon cables, connect the MCU to the input and output devices. We have used a relay & transistor circuit to switched between 12v supply to the vacuum pump and 5v MCU data pins. The electronics sans the coffee gripper&SRF05 are put into a pouch follow by the coffee gripper & SRF05 are assembled into a glove that is fastened with velcro. Airline tubin, VCC and GND wires, data wires are then secure using heat shrink tubing and secure along the arm to the pouch.

Step 5: How it works. The SRF05 will detect the distance between the gripper and the surface. Once the coffee gripper is placed upon the object to be picked up and the distance is within the threshold, the vacuum pump will start removing air from the balloon filled with coffee to create a grip surrounding the object. Releasing of the object follows similar methodology.