It's so simple - you can wire it up "free-form" without a circuit board in about 15 minutes.
All parts available at Radio Shack for under $9
Supports PWM for variable speed control
Handles up to 5 amps peak / 2.5 amps continuous (5 amps continuous with heatsink)
Controlled using just two pins - "enable" and "direction"
Requires at least 7.5 volts to operate
Relay is rated for "only" 100,000 cycles and may not be appropriate for some high vibration projects
Doesn't provide motor "braking"
The most common way to provide reversible motor control is with an H-Bridge. A basic H-Bridge is made up of 4 transistors - but commonly end up requiring more like 10 components when you include things like flyback diodes and secondary transistors.
I wanted something simpler for a CNC project I'm working on - so I came up with this design. I'm fairly sure I'm not the "inventor" of this circuit - but it's not widely documented. As far as I can tell it doesn't have a name.
I am hereby naming it the RAT Controller. RAT being an acronym for Relay And Transistors.
Step 1: Stuff You'll Need
The same parts are available online for under $4.
12VDC Coil DPDT Miniature PC Relay
Radio Shack Part: 275-249
If purchasing online - try searching for "OMI-SH-212D"
2 x TIP120 Darlington Transistors
Radio Shack Part: 276-2068
2 x 220 Ohm Resistors
Values do not need to be exact.
A TO-220 size heatsink such as Radio Shack 276-1363 will allow this motor controller to provide 5 amps continuously as opposed to just peak. You'll also need a #6 screw and nut. See the final "Notes" step for information on installing or making your own heatsink out of a pop can.
You'll also need:
And solder - any gauge is fine.
You'll need some kind of hookup wire to make connections and interface with your microcontroller.
22 Gauge Solid Core Hookup wire works well and easily fits into Arduino headers.
Available at Radio Shack - Catalog # 278-1221