PWM vs. HIGH

[wdmagic]

first here is a good layout for using dc motors with a FET and a PIC, NOTE C3 and C4 are optional if your using motor case to ground.

now as for using that other chip, I dont have the datasheet here right now to look at, but I usually use either a DPDT relay or a FET H-Bridge circuit for reversing, depends on the amps needed. for tiny DC motors a relay is a pretty cheap way to go, and requires no special circuitry. an Hbridge requires 4 fets and a couple transistors but can handle any amperage based on the FETs used. you can also use a lm298 I beleive, as it has dual hbridges built in. but only allows for a certain wattage.

[RossWaddell]

The SN754410 has an H-Bridge built in and eliminates the FET and diode.



(Ignore the bumf to the bottom left - it's for a button input to change the direction of one of the motors)

[HenrikOlsson]

Just a quick note regarding the circuit in post #7.
For basic on/off control it should be fine but be careful IF you're going to use it to control the speed of the motor by PWM'ing the gate of the MOSFET. The 330uF cap across the motor terminal will present a very low impedence path (basically a short) at any considerable frequency.

Perhaps the capacitor was meant to bypass the power rails (like C2) and not across the motor?

/Henrik.