FIGURE 1. All of the hard stuff about implementing H-bridges
is taken care of in the input section of the Si9986.
devices. You can build them from scratch or obtain them
prepackaged. They come in high current versions or low
power, low current versions. Their ability to place opposite
polarities on the attached load offers a ton of functional
possibilities. A good example of an H-bridge that is well
suited for low power applications is the Si9986. The Si9986
is able to switch up to 12 VDC with a continuous load of
1A. The eight-pin Si9986 is also suitable for PWM (pulse
width modulation) applications as it can switch at
frequencies up to 200 kHz. A block diagram of the Si9986
is constructed in Figure 1.
FIGURE 2. You can equate the Si9986's four output
states to motor terms such as forward,
reverse, brake, and free-wheeling.
PHOTO 2. You can assemble a basic H-bridge from discrete
parts that will probably cost less. However, if your code fails
to switch the active components of the H-bridge correctly,
you will release the magic smoke.
SCHEMATIC 2. A small
modification to the
base design offered up
in Schematic 1 results in
a microcontroller-based
Si9986 H-bridge
controller.
52 SERVO 06.2013
