Which microcontroller? That's still not etched in stone but the prototype
is build around a Basic Stamp 2. (http://www.parallax.com/) The BS2 is one
of the more expensive micro's out and it's got a limited feature set
compared to some newer micro's. But it's old age does have a couple of
advantages, lots of add on hardware is out there and it has a large support
community. I also bought a Z-World Jackrabbit
(http://www.zworld.com/products/bl1800) but Mr. UPS hasn't dropped it off
yet. I'm also seriously interested in the Oopic (http://oopic.com/). And
there's a couple of others in the running too but who's names escape me at
the moment.
It's entirely possible for the BS2 to measure pack voltage/amperage but the
Alltrax has all that and more in it's microcontroller. It just makes sense
to ask the BS2 to get that info from the controller and simply show it to
us. I have a hall effect sensor hooked up to the BS2 at this point to
measure wheel rotation. From that we can get speed and, if we're not using
a tranny, motor RPM too. There's a few ports leftover on the BS2 to measure
the motor temp - important for those of us running Eteks! I have a servro
hooked up that moves in relation to speed sorta like an analog speedo.
It's kinda cute but doesn't work how I'd like yet.
I was thinking of doing something along these lines as well. I have a
couple of BS2's laying around and enjoy playing with them. The biggest
problem I see going this route is that data from the controller is on the
motor side of things (I think, but I'm not positive). Generally when we
look at volts and amps it is to keep the battery pack in shape, so we really
need to look at what is going on on the battery side. Now that I think
about it though, I be making an incorrect assumption about the data the
Alltrax provides. Perhaps I need to strap the old laptop on and go for a
ride.
Anyway after considering this option for a number of months I decided that
an E-meter is probably worth it's price and bought one off of the
Grassrootsev site. They didn't have the correct prescaler, so I had to find
that elsewhere. At a total of about $370 this turns out to be the single
most expensive component I have bought for the bike so far. To justify the
cost I am wrapping it up and putting it under the Christmas tree, so no
playing with it until after Christmas :-(
damon
