November 2006

Zilla FAQ14 Nov 2006 12:18 am

Recently someone on the EV list asked if I have my “ears on”. I think it was Lee Hart, the best EV list contributor of all time since I started reading the list around 1994.

Yes, I do occasionally see posts from the EV list if they mention my name due to some automatic filters, but I am not subscribed and so cannot write back to the list. I’ve been a bit too busy with production lately to deal with the large volume of EV list email.

To address the question about multiple processors:
The Zilla and Hairball each have one PIC processor with hardware watchdog timers and many software catch-all protection systems. Ironically it’s actually quite hard to get a Zilla to run at all, everything has to be just right.

The Zilla processor controls the power section and can only be reprogrammed at the factory. It has pretty stable code in it that rarely changes since it does such a important job of protecting the power devices. The Hairball processor controls the contactors and many features and can be reprogrammed in the field. I consider it more flexible since a Hairball error should never cause a Zilla power section to fail. The Hairball and Zilla communicate through a nonstandard bus on Cat 5 wire which is very noise immune. (It’s not ethernet, don’t try to use cat 6 wire) If either unit loses communication with the other, it will shut down the power output in a very short time (less than 250 ms). This is done either through the Hairball by way of the main contactor and/or the Zilla power section by shutting off the IGBTs. I do it this way so that if either system fails for any reason the other will shut down power to the motor in less than one quarter second and avoid a runaway condition.

Of course all these safeties allow opportunities for false trips. At this time there is a problem I am working on which seems to affect low voltage systems (156V and under) setting 1123 errors right near full throttle and shutting down. If you are having such a problem, be sure to contact me to get me to fix your Zilla power section with (you guessed it) a code update.

During normal operation the Hairball sets the variable user voltage and current limits and does most of the safety checking while the Zilla primarily protects itself, reports status and data back to the Hairball and keeps the fast things like the multiple current and voltage limits in safe ranges.

I hope this clarifies things a bit.

Production Notes13 Nov 2006 11:41 pm

Hello All,
It’s been two weeks since Carbon Black Monday and all is not yet well at the Cafe Electric shop.

In the time that has passed I have built a clean room with HEPA filtration, a new clean workbench, super fine grease filters and a new clean workbench surface. I’ve cleaned and reassembled one of the Z2K’s and then ran it through a number of tests which are not yet encouraging. I’ve scratched my head a lot. I took mental breaks by hiking in the rain and even beating air molecules into submission around the local CVO traffic pattern. I’ve been investigating the tin plating process on the copper bus bars which is currently a prime suspect for our troubles. Tin plating is one of the processes that changed with the move to local Oregon suppliers. This has been on my mind especially since my first thought of dirt contamination did not turn out to be the problem. Plating houses have a reputation of being sloppy, and I am just realizing how lucky I was to have Hy-Tech plating in San Carlos when I was down in Kalifornia. They sure knew what they were doing down there. Unfortunately it’s a bit tough to carry half a ton of copper to California for plating.

Today some good progress was made when I built a micro-Ohm-meter (utilizing as probes olive skewers from our local and fancy “Ink Well Home Store”) which is allowing me to check the contact integrity of many power parts (while theoretically in parallel with very heavy copper) after final assembly. This was previously not possible with the tools I had. This test has shown that despite the clean room issues which I resolved, the problem which caused the Z2K to fail still exists and I have more research to do.

In the meantime, the 13 remaining Z2k’s are being disassembled and cleaned (by my assistant who is doing a wonderful job) for reassembly when I do find the cause of our current problem.
It is both good and bad news that until I resolve this issue, I can not ship any controllers. This is just the type of thing that could show up as a long term reliability problem even if the controller does pass bench testing. The good news is that I won’t let you get such a potentially unreliable controller. The bad news of course it that I do not know when we will begin shipping product again. As a result the Z1K’s that I hoped to start shipping in two days are on hold until the problem is resolved. All the parts are still waiting on the shelf for final assembly. If we are lucky then it will only take a few more days to resolve the issue. In that case I could start shipping March orders for Z1K’s in December right after the Z2Ks go out. If we are not lucky then it will take longer, could be weeks, or months. I’m sure hoping it’s not months!

So, that’s the latest from the very wet Willamette Valley in Oregon. I’m sorry I don’t have better news. I’ll send another update after I turn 40. 🙂 Don’t worry, that’s in less than a week.