Is it good practice to use optocouplers on an hbridge?

rwgast_logicdesign

So i have just discovered the world of opto couplers and the first thing I thought theyd be cool for is isolating an h bridge circuit. I guess what Im wondering is if using an motor control IC like l293 or l6205 is there a huge need for opto couplers if you have good decoupling and flyback systems in place also where would generally want to isolate the hbridge, would you stick the optocouplers on the signal line in lines?

Mike Green

Why would you need an optocoupler? These are necessary when you want to isolate two parts of a system with different ground potentials, particularly useful when you're running part of a system off the AC power line with that ground being the neutral side of the line and another part of the system either running off batteries or an isolated power supply with its own ground.

An H-Bridge usually is controlled by logic level inputs fed into the base of power transistors or some drivers or logic ahead of the power transistors and this isolates the logic level inputs from the relatively high voltage feeding the motors. You might have optocouplers further isolating the inputs if you wanted to protect them in case of failure of the power transistors. The problem is that most optocouplers are slow and the fast ones are expensive.

tonyp12

Not needed unless you plan something heavy duty with your own mosfets and need gate drivers anyway
,you could go for a Isolated driver.
http://www.mouser.com/ProductDetail/Silicon-Labs/Si8234AB-C-IS/?qs=sGAEpiMZZMsqIGqlaWy0RHXgwO1U%252b0zS