Block diagram optical isolated h-bridge.

Fig. 1

Optical Isolation H-Bridge Motor Controls

by Lewis Loflin

What's new?

For November-December 2014 this website decided to focus on practical transistor theory both bipolar and MOSFET. This included a series of 10 You Tube videos three on constant current source circuits, one on the PIC12F683 micro-controller, most of the rest on transistor circuits. This included several new pages and extensive updates and new graphics for several others.

The particular interest of the reader seems to be motor control circuits for robotics and 3D printers. This page and the associated video demonstrate the following:

The use of opt-couplers for electrical isolation between a micro-controller and higher-voltage motor drive circuits can prevent a lot of problems.

The use again of opto-isolation with the use of series speed control circuits placed in either the ground side of an H-bridge or in Vcc. This video used the ground side while the page on the TA8050P H-bridge control used the Vcc side.

While the video used a PIC12F683 which happened to be what I was doing a separate video and webpage on, the very same circuits work identical with Arduino or other micro-controller.

Fig. 1 show the PIC12F683 connection to the H-bridge module. The grounds are separate in order to insert the speed control circuits in the ground side of the motor power supply. I could tie the two power supply grounds together and insert the PWM control in the +Vcc side of the H-bridge.

Fig. 2

Fig. 2 shows the schematic for this particular MOSFET H-bridge. The digital ground from the micro-controller is separate from the motor power ground.

Fig. 3

Fig. 3 shows the speed control circuit. The speed is controlled by pulse-width modulation.

See:
Opto-Isolated Transistor Drivers for Micro-Controllers
Pulse-Width Modulation Tutorial

Fig. 4