Electronics / Controllers: August 2009 Archives

When I was first starting out with the Piaggio conversion, I was monitoring my power consumption using a Doc Wattson / Watt's Up. Good for checking on amp-hours used, voltage, etc.

A few weeks into the conversion, I dropped my bike chain on the Doc Wattson and broke the LCD glass. Very annoying -- they should provide a lexan cover on things like this that will get banged around.

I asked the manufacturer if they did repairs and they didn't. I asked them for the spec on the LCD and they said it wasn't divulge-able. They did give me a discount on my second one and I threw the old one in my "crash" bin.

Well, fast forward a few months more and I've been working with STAMPS and PICs and know a bit more about LCD screens -- especially how most 16x2 displays are driven using the same HD44780 IC chip.

Time to open the Doc Wattson up and see what's in it.

More after the jump

This is the post-flameout, rebuilt Piaggio Boxer EV. I changed the battery carrier from a top-mount system to saddle bags. This lowers the center of gravity and makes it easier to handle. I'm going to replace the seat with something more classic looking.

I welded the saddlebag carriers myself from steel tubing with my MIG welder.

The Electronic Speed Controller (ESC) is sitting on top. It's the replacement HV-110 that I received from Castle Creations with additional capacitors soldered in parallel on the input lines.

It's sitting in a Lexan enclosure that I bodged together. Unlike the old metal enclosure with a single temperature controlled fan, the new enclosure uses two fixed speed fans that pull the air across the ESC and the voltage converters (sitting below). They also are assisted by draft air when the vehicle is at speed.

This photo was taken a few minutes after a short run, the temp of the caps is 34 centigrade which is nominal. Anything less than 60 centigrade I think will be ok. The caps are rated at 85C.

Although the angle of the photo above makes it look like the ESC could short out on the voltage converters, it's actually held a centimeter or so above and everything is well insulated.

As I mentioned in a comment, I've been playing with microcontrollers these days. I started out with a BASIC Stamp2 system which was great and very educational, but quickly ran into its limitations -- the main one being financial, each STAMP is around $40-50 which limits its applicability.

But the advantage of the STAMP is that it's very easy to program (in BASIC!) and that it has the ability to pulse PWM to control RC servos, which makes it ideal for EV projects.

On my explorations for a cheaper microcontroller, I came across the open source Arduino which was fantastic except that it was still expensive ($20 / chip for the cheapest) and the programming environment was more fidgety that I liked.

The solution appears to be PICAXE. The cheapest one is $3 / chip (wow!) and it can do full time PWM as well as has a A/D converter right in the chip. And its fully scalable as well. The BASIC programming language seems very similar to the STAMP and runs on Macs, Linux, and MS.

$3/chip for the 8M means that I'll be able to place them everywhere! Cheap is good!

Extremly cool. Must watch. The one problem I currently see in it is that cell-phone cameras are often fixed focus and can't go to infinity properly, which would disrupt the Bokode. But as cell phone cameras improve, the Bokode applicability should also improve.