NPN Transistor Drive For SMA (MEC145E)

This circuit is part of my book Robotics, Mechatronics and Artificial Intelligence (sold out) published in the United States. It can be used to control SMA (Shape Memory Alloy) and other DC loads in robotics and mechatronics projects.

Figure 1 shows a simple block using an NPN transistor driving an SMA (electronic muscle) up to 2 A. This circuit needs 20 mA to drive an 1 A SMA and less to drive lower-current muscles. TTL and CMOS outputs can drive low-power SMAs using this block.

 For higher gain, driving loads up to 1 A from TTL or CMOS outputs, you can replace the transistor with a BD135 or BD137. In any case, the transistor must be mounted on a heat sink.


Figure 1    NPN driver for SMA.
Figure 1 NPN driver for SMA.