Well... a LOT to write about regarding Project 16. So, in no particular order, here are some observations, notes, etc.
* I used the SN754410 IC in lieu of the L293D. The author reports the L293D chip builds up a LOT of heat, but I didn't really encounter that problem. It may be either because I didn't let the single motor run for more than 20-30 seconds OR the small motor I'm using may be a factor... just don't know.
* Reader ctdahle provided a comment for Project 15 that clarified the issue of motors requiring their own power supply and not pulling from the Arduino. Understood, and thank you for clearing it up! This time around, I put in a single 9V battery (see photos) that I felt would do the job.
* Although it isn't easy to tell from Figure 5-3, the IC chip needs to have pin 1 pointing left... towards the Arduino. You can figure this out easily enough with the program and the pin layout on page 109, but I figured I'd save you a few seconds and tell you.
* I tried to use a heat sink that I purchased for this project... it slides over the IC and makes contact on the top of the chip. The problem was that with the heat sink, I couldn't insert the chip into the breadboard. I also tried a 16 pin socket (see photo of socket and heat sink) but the heat sink also prevented the chip from being inserted into the socket. The author shows what appears to be a heat sink that must require the chip paste but I couldn't find that particular item at mouser.com or allelectronics.com. (A quick search of earthshineelectronics.com - the author's werbsite - didn't show anything for "heat sink" either, so please tell me if you find it and where.)
The program works fine... I am able to flip the toggle to change the direction of the motor spin. Once again I have to crank up the potentiometer quite a bit to get spin, but once it's spinning and I flip the toggle, you can hear the motor stop for a moment and then start up spinning in the opposite direction. (Not sure what the purpose of the 10k resistor is on the toggle - can someone offer an explanation? It looks like it's simply serving as a pulldown resistor... but no mention in the book.)
I was going to attempt the variation of this project (see page 109) but I'm including a closeup photo here of one of my tiny DC motors. As you can see, the wire has broken off... the leads on these tiny motors just can't hold up to even the slightest of tugs... will have to re-solder a stronger wire soon.
Sorry for the rat's nest of wires again... I simply love these flexible jumper wires and I'm not really trying to use any kind of color coding right now... maybe later. That said, if you look closely at some of the photos, you'll see I didn't follow the author's wiring diagrams exactly - the 9V positive wire connects directly to the chip... same with the motor wires. I just basically ignored where the author used jumper wire to continue a connection elsewhere.
Video below... you can hear the change of the motor when the toggle is thrown.