I got the board fully populated yesterday, plus I made a heat sink out of a piece of ¼” × ¾” aluminum bar stock. The heat sink makes an enormous difference. Before using it, running a small motor at low power for 20–30 seconds was enough to make the H-bridge uncomfortably hot. Now running the same 12v motor stalled at full current (3A) for a full minute raises the temperature only to 100ºF.
The motor got warmer than that, and I think I burned it out, since it no longer runs and has a 400kΩ resistance. I’m not really surprised—it was a cheap door-lock actuator, and only intended to be used with fraction of a second pulses. Further testing will require a more robust motor.
As you can see from the photo, the screw terminal for motor 4 (second from the bottom) is a bit crooked—I’ll have to unsolder it and straighten it. For the HexMotor 2 board, I’ll use slightly smaller holes so alignment is easier.
The thermal grease I used (Cooler Master IceFusion High Performance Thermal Compound 40G RG-ICF-CWR2-GP) was more liquid than I expected, especially since it comes with a little spatula for applying it. I had to put on a fairly thick layer, because the aluminum extrusion was not very smooth, and when I tightened the bolts the stuff oozed out making a sticky mess. Next time, I’ll sand the aluminum smooth first and use much less thermal grease.
This closeup photo, in addition to showing the pooled excess thermal grease, shows the header pins with shorting jumpers to configure the H-bridges for either lock antiphase or sign-magnitude control. (Because of the last-minute change from TLE-5205 to TLE-5206 chips, the silk-screen labeling of the header pins is wrong—this board is actually configured for sign-magnitude throughout not lock antiphase.
The photos also show that I did not leave room for the heat sink between the electrolytic capacitors. The HexMotor 2.0 board will fix this problem also.
The HexMotor software now can handle 3 different boards: the HexMotor rev 1.3 board shown here, the Adafruit Motor Shield, and the HexMotor rev 2 board, which I am just about done fussing with the design for. I’ve only tested with an Arduino Duemilanove board, but the software should work with an Arduino Mega as well.