Rethinking the Nv net
By now you should have familiarized yourself with the basic 6 Nv microcore circuit. But a little math and you'll notice that with two motors and two directions each, 4 Nv's would seem appropriate. For basic walking function only 4 of the 6 available Nv's are needed in a two motor walker (although 6 makes for a whole new set of behaviors), so rebuild the basic circuit so you get this....
Have no fear the other two Nv's will be useful later...
The 74ALS245 is an octal bus transceiver designed for data transmission. Well, we're going to use it to drive motors. If you've chosen you motor / gear combination properly then this won't be a problem. If you dig up a TTL data book you'll see that the 245 has 8 bidirectional non-inverting amplifiers each capable of driving 50 mA, a direction pin (Dir) for selecting which way through the chip and an enable pin (E).
Note that the ALS ve
rsion has been found to be the best for current, feedback, etc. CMOS (HCT, HC, C) will work but they lose a little in the feedback. They do consume less parasitic power so for Solar Powered|solar apps]] they are the better choice.....
Editor's note: the 74ALS245 will only work well with a supply voltage of between 4.5 and 6.0 V -- unless your source is within this range, you'd be well advised to use a 74HC245 instead
Ganging up for
CurrentIf you've tested your motors you probably find that they need a little more than 50 mA to do anything useful.
[Editor's Note: This will depend on the motors selected for the task]
If things aren't right change the motor polarity on one of the motors and it should work.