The Third Arm Claw is a mechanism designed to be used by someone who has trouble bending over and uses a cane to walk. The following is a prototype for a cane attachment that can snap onto any standard sized cane. The mechanism is a claw that extends from the cane to grab items such as keys, cloth, and small coins. It also contains an LED light and a sensor for Black Ice. Surveys show that nearly 30 million Americans experience back pain of some kind and would be benefitted by a cane attachment such as this.


- High Torque Motor

- Arduino Nano

- ADAFruit Proximity Temperature Sensor

- LED Light

- Motor

- 1 long screw

- I short screw

- 2 coupler

- I plastic cylinder

- C rail

- Long piece of wood

- 2 wooden blocks

- Switches


- Hot glue gun

- Power drill

- Band Saw’

Step 1: The Base and Sheath

The base is a piece of plywood. Two wooden blocks are situated at the ends of the plywood. Underneath them, there is a sheath for the long screw. This can be made out of foam and duct tape. The screw is inserted into these. At the top of the mechanism, hot glue a motor onto the plywood and attach it to the screw using a coupler.

The sheath for the mechanism is made from two long metal rectangles. We used a C rail cut in half. These should be glued to a long wooden piece to form a rectangle with an open top.

Step 2: The Claw Sled

To make the sled for the claw mechanism, situate a high torque motor on the piece of metal you are using as the sled base. We used the same C-rail so it fit neatly inside the sheath. The sled is glued to a rubber cylinder slightly larger than the screw and put on the screw. This allows the sled to move up and down the screw as it is rotated.

Another screw is attached to this motor. Drill a hole in a plastic cube that will allow it to be screwed onto the piece. Screw a screw into the cube, leaving it slightly overhung.

Step 3: The Claw Mechanism

Insert a four pronged claw with a long wire tail into an old pen. Attach the wire tail to the screw in the block. Attach the actual claw to the end of the screw by running a long metallic rod through the plastic block and alongside the screw. Wrap some electric tape around the rod and the bottom of the pen. This should secure the claw piece in place.

Step 4: Sensors and Controls

The temperature sensor is glued into a cardboard covering. Connect this to the bottom of the mechanism. Run the wiring for this up the side of the piece and into the control panel. Our control panel was made out of a small box. Inside the box should be the Arduino Nano, the battery packs for the motors, and a buzzer. Drill some holes into the box in its top face and poke the switches and the LED through the top.

Step 5: Arduino Code for 3RD Arm

The goal of the code is to set off the buzzer and the LED when the temperature sensor senses a temperature lower than a set number. For example, if the temperature is set to 25 degrees Celsius, anything below that will set off the alarm and light. The temperature should be easily adjustable in the code. See attached Arduino code.

About This Instructable




Bio: The BCAMRL is a Mechatronics Research Lab, found on the campus of Bergen County Academies a magnet high school within the Bergen County Technical School ... More »
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