This mini actuator stands just 9.2mm tall and could be used as a source of haptic feedback in a variety of devices. I developed it while working on a project to aid those with visual impairment. I wanted to see if I could create a more localized haptic feedback source, unlike vibration motors, while still keeping the over all size as small as possible
Step 1: Parts/Equipment
This actuator uses a very small coil of 0.05mm wire and 2 small 3mm by 1mm cylindrical magnets and is brought together with 3D printed parts.
For the Coil Actuator
1. Mini Actuator coil - Available from Microwings
2. 2x 3 by 1 mm cylindrical magnet - (or one 3 by 2 mm) - Available from Microwings
3. 3D printed base, pin and enclosure
2. Super glue/ Araldite
1. Arduino uno
2. H bridge driver
3. Bread board
Step 2: 3D Printed Parts
All Parts where printed in ABS plastic on an UP Box printer using it's highest resolution
This actuator consists of three 3D printed parts
1. The Base
2. The Pin
3. The Enclosure
The files are available below
The Base is where the coil will sit, the Pin is attached to the magnets and the enclosure keeps everything together.
When a voltage is applied to the coil one way, it will repel the magnets which will push the pin upwards through the hole in the enclosure. When the voltage is reversed the magnets and pin are pulled back down inside the enclosure.
Using a H- Bridge driver and a PWM signal we can change the pulsing speed and intensity of the actuator.
Step 3: Putting It Together
Putting this actuator together is a bit fiddly due to the small size of the parts, tweezers are recommended.
1. Add a few drops of Super glue (I used Araldite) around the sides of the cylinder on the base component.
2. With the tweezers drop the coil over the top of the cylinder on the base, make sure wires of the coil are clear.
3. Using the glue again, attach the magnets to the base of the pin, making sure it is as closely aliened as possible.
4. WAIT until the glue has FULLY dried before the next step!
5. Drop the pin and magnets into the enclosure and wiggle the magnets around until the pin falls into the small hole in the top of the enclosure.
6. Glue the enclosure onto the base, making use of the little notch in the bottom of the enclosure for the coil's wires.
DO NOT TEST UNTIL GLUE HAS FULLY DRIED
- the thing will rip itself apart
Step 4: Testing
To test the actuator, you'l have to solder some thicker wires to the thin wires of the coil. I also recommend wrapping the thin wires of the coil around the enclosure and gluing them down as these wires WILL break if handled too much.
To test my design I used Arduino uno and The A4973 Full Bridge Motor Driver.
This motor driver is a bit overkill for this coil and a simpler H-bridge would work too.
The wiring for the motor driver is available above
Using the Arduino I simply generated an alternating output to pulse the coil and move the pin (see code)
Step 5: Testing - Continued
Here is a short video of the actuator working, as you can see it is able work at all angles and different speeds.
This actuator doesn't have enough power to keep the pin up when it is being pressed down by a finger, but by pulsing it like this it'll give you a very noticeable, and localized, thump.
The next step will be to put a number of these into an array and see how you can send people different types of information.
Thanks for reading!