Tendon Vibrators

Tendon Vibration

Tendon vibration can result in a sensory illusion in the motor system. Just like a visual illusion you can trick your nervous system to “feel” something that is not actually real. Tendon vibration can cause a sensory illusion to the motor system by disrupting the brain’s perception of limb position.

Other interesting sensory illusions include:

Tendon Vibrator

You can build your own tendon vibrators using the materials outlined below, and if you have access to a 3D printer you can use the attached SolidWorks files (MotorTube.SLDPRT and WeightRotor.SLDPRT) to create a housing and eccentric mass for the motor. You can add solder to the void in the rotor to add necessary eccentric mass. The two halves of the motor housing are symmetric and are held together with a standard o-ring.

Parts List

Mabuchi RK-370CA-18260
- Source for purchase: All Electronics.com
- Round housing (24.4D x 30.8L mm - 2 mm shaft)
- Carbon brushes
- 3 poles
- Rubber magnet
- 260 windings of 0.18 mm wire
24.4mm diameter x 30.8mm long. 2 threaded mounting holes (M3.0 x 0.5) on 17.0mm centers. 2mm diameter shaft x 10.5mm long.
O-rings for motor housing
- Source for purchase: McMaster # 9262K188
Width: 2 mm
OD: 27 mm
ID: 23 mm

Velcro arm band
- Source for purchase: Amazon
9-volt battery
Terminals for 9-volt battery

Vibration Force

The basic formula for determining the applied vibration force from the unbalanced rotating mass is simply:

$|F| = mR\omega^2$

This is where ω is the shaft speed of the motor, m is the total mass of the unbalanced object and R is the distance from the pivot point to the center-of-mass.

The completed project: