Shape Memory Alloy actuators
Hey guys!! Ever wanted to configure the flexible and lightweight shape memory alloys for developing your own actuator. If yes, you are going to start real adventures. And in this blog, I would like to share my experience and learning that would help you fasten up building a proof of concept using shape memory alloy.
1) SMA alloy used — from flexinol, 150um diameter wire.
Flexinol is selling pre-trained shape memory alloy wires/ springs/ strips, of various diameters easily configurable with projects. For more details check out at, https://www.dynalloy.com/flexinol.php.
2) Power Supply — Li-ion battery, 3.7 V
Choosing the battery has taken me through a journey of choosing the right batteries for the projects and understanding the specifications of the battery. Specially SMA wires need higher current values to get heated up and to actuate. In my project, 500mA constant current for 2–3 secs is required to actuate the actuator.
As Li-ion batteries have enough mAh and C rating they were a good fit for the project.
Check the following link https://circuitdigest.com/article/an-overview-of-li-ion-batteries, to understand terminologies about Li-ion3 batteries.
Controlling the power supply to SMA wire is the critical job of developing an actuator using Shape memory alloy. (Note: As the current output from most of the development board, like Arduino, is around 40uA we could not power the SMA wires directly from their control pins)
As I was building a proof-of-concept I confined with using relays, as they could 500mA currents. (Note: Also you could use voltage / current controlled transistor as a controlling element for a real project. Check the datasheet for current handling capacity before buying one.)
I have used node MCU for controlling the actuator remotely using a mobile app that has been configured using, BLYNK app.
(Note: While controlling Relay using NodeMcu connect the Vcc of Relay module to 3.3V power supply of NodeMcu.)
The connection of SMA wire with the copper wires is generally done by crimping the SMA wire with copper wire, (you could spare your jumper wire and could notice thin crimping beads in them, which I have configured for my project.)