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.

21 Responses to “Two Processors in a Zilla?”

  1. on 27 Nov 2006 at 8:14 pm Craig Mueller


    Now that we have the processor news, lets get down to a very serious question… why did you name your controller the ‘Zilla’ (presumably, Godzilla – relating to the Japanese movie character of the 1950’s)?

  2. on 06 Dec 2006 at 6:56 pm Otmar


    You’ll have to ask John Wayland about that. He’s the father of many EV controller names.

  3. on 22 Dec 2006 at 5:53 am Dan Frederiksen

    what IGBTs do you use in the zillas?

  4. on 22 Dec 2006 at 10:59 am Otmar

    The good ones. 🙂

  5. on 22 Dec 2006 at 5:51 pm Dan Frederiksen

    so much for idealism you greedy little bastard : ) afraid that if someone does the math on the parts that you will look pricey?

  6. on 22 Dec 2006 at 6:34 pm Otmar

    Well Dan, so I’m a greedy little bastard eh?

    Ya know Danny boy, I shouldn’t let it bother me since your impolite request with no offer of anything in return, not the care to capitalize your correspondence or even the bother to put a interesting story around your request, shows that you’re probably a immature juvenile raised with the expectation that all work should be done for you for free. Or if not juvenile, then you’re probably a impolite older person with developmental disorders. But still it bothers me.

    Maybe it’s because I did inventory today to see how I did this year. So after working at the shop most of the year, plus floating $80K in inventory, what do I have to show for it? A net loss. Yup. It’s jerks like you that tempt me to run off and do fun things that also make money instead of slaving away producing controllers. Fortunately you are the minority, and many people are grateful for the sacrifice I make to support the hobbyist EV market.

    If you really think you can make a reliable controller for less than I’m selling mine, by all means do so. Chances are you’ll go the way of DCP, Auburn, Stan Obcamp, etc who all went out of business trying to do the same while I watched them come and go. Unfortunately most of these people managed to make a cheaper controller, took many peoples hard earned money and then folded when it became clear that those cheaper controllers didn’t have the required reliability. So no, I’m not going to help you build yet another unreliable controller. If you’re at all capable at building a decent controller, you certainly won’t need me suggesting which IGBT to use. So go ahead, try, if you succeed at doing it, I’ll gladly give up production and do more fun things.

    Oh, and since I just did inventory, I can tell you that the IGBT’s in a Z1K cost me $165.60. Which is just one reason you sound like an idiot. You see, IGBT’s are actually one of the cheaper parts of a controller and knowing their cost in no way represents what it actually costs to build a reliable controller. Shucks, It costs more than that for the copper.

    In the meantime, feel free to go back to your video games where success is easy. Or if you prefer, do a great controller design, manufacture it and I’ll gladly shut down Zilla production and do all those other design projects that are waiting for me. But don’t expect me to give out design details to some rude web troll.

  7. on 22 Dec 2006 at 10:00 pm Dan Frederiksen

    if you are running without profit then why so coy about the details?
    I would love to hear which 1000A IGBT is so inexpensive. also a bit curious how the copper could be more expensive but mainly the IGBT. please do tell. I’m not looking to replace you but I am hoping to achieve a cheaper and working product. if it’s such a sacrifice for you then I would hope you would help others help you with the burden

  8. on 22 Dec 2006 at 10:17 pm Otmar

    Oh man, why do I fall for this.

    You’ve got TROLL written all over you, but I’ll try to give the benefit of the doubt.

    Why am I coy about the details? Because I may not have made a profit this year, but I do have over ten years of hard work invested to get to this stage.
    Also it’s rather boring to help lazy people like you. I do mentor a few people on power electronics, but they have shown dedication and willingness to learn. I find people like you very annoying. Please go away and do some work yourself.

    Ok, maybe that’s to vague for you, let me be more specific:
    Here is your nice simple assignment:
    Find a IGBT arrangement that allows 1000 amps at 300 volts nominal with a case temperature of 55 degrees C for under $250. Don’t forget to include both conduction and switching losses. Figure a 15 khz switching frequency. If you parallel more than one then be sure to include worst case derating for reasonable matching tolerances.

    Here’s a hint, I buy $20,000 worth of IGBT’s at a time so that I don’t have to throw away more than 10% of them.

    OK, that’s the last I waste my time on your laziness. All future posts of yours will be deleted until you come up with a correct answer and provide the math to support it. You can send it in acrobat if it’s not easy to show in text.


  9. on 19 Feb 2007 at 9:21 am Andrew Hanlon


    While I agree entirely that Frederikson was way out of line in his comments, it seems a reasonable, and understandable request to ask for some information about the internals of your product. Especially since, given your followup comments, the IGBT is the least of what goes into a good controller.

    Now while I understand that there is a decent warranty attached to your product, they are sold to a community that by nature are a group of experimenters, and as such there are many who will use (or abuse) the controller in such a manner that it is not covered under warranty. To these people knowing how expensive or possible diy repairs to the controller would be, could be a major selling point. Anyway, no one would expect you to post up a schematic and source code, but the topology ( such as do you use single IGBTs or paralleled) would, in my opinion, only make your product that much more appealing. I don’t think anyone would look at your controllers and say they’re overhyped or priced as there is truly nothing comparable in specs on the market for cheaper.

  10. on 19 Feb 2007 at 9:56 am Otmar

    Hello Andrew,
    Fortunately I have not yet seen a Zilla power section failure in the field. Those who have done business with me over the years know that I do what I can to keep any non-warranty repair costs to a minimum. Our standard policy is to do out of warranty repairs for no more than our cost. Updates to code and the like we do for free charging only for shipping. We have had to repair a number of Hairballs that were run under water, exposed to high voltage and connected to contactors without the snubber diode installed. I even have one dealer who learned to replace the contactor drivers himself with my guidance. Fortunately those rather simple repairs have been the worst that I’ve seen. One of the primary reasons for the separate Hairball is to protect the power section from damage in such cases.

    That said, you are correct that people should know about the possibility of diy repair. The bad news is that if a power section does have a catastrophic failure (such as the one I blew up in the shop a few months ago) there is very little hope of salvaging parts. If it’s not too bad then $100 to $200 in hardware can be reused, but the pc boards and all electronic components are usually not salvageable. The Zilla was optimized to be compact and relatively inexpensive to build. (and yes, part of the design involves very careful matching of IGBTs, we match enough for over 100 controllers at once to insure tight sets). Even more so than the hard to repair Curtis, the Zilla has no provisions in the design for rebuilding it. Since we generally can not rebuild a totally blown power section with all the resources in the shop, I believe it would be extremely unlikely that some other engineer could pull it off.

    It is important to put this in perspective. High voltage controllers rarely can be rebuilt after a power section failure. The old GE controller is a notable exception. It had a couple IGBT’s in parallel that could be replaced if you could get a matched set for them, and I believe the Kilovac controller is similar. But blow a Auburn, Curtis, DCP or Zappi and the chances are that the plasma ball of the failure will make most of the leftovers unusable. In most cases the heatsink, outside cover and bus bars are all that survive.

    I hope this clarifies matters.

  11. on 19 Feb 2007 at 10:11 am Andrew Hanlon

    Thanks, it clarifies things for the most part, though in checking the rest of your website, it seems rather hypocritical to have the schematic up for a rival company and yet be so tight with your own “secrets”…

    Anyway, good luck with it all.

  12. on 19 Feb 2007 at 10:27 am Otmar

    I don’t consider it hypocritical.
    Curtis treated me badly when one of their controllers blew up and they would not honor the warranty. I spent many hours reverse engineering the product (and found it should have been covered by warranty) and therefore feel quite OK posting it.

    I realize that someone else could buy one of my controllers, put in the work and publish details about my design as well, but it does not seem to me that I should be morally obligated put it out there myself.

  13. on 21 Apr 2007 at 6:59 pm Peter Fynn

    I have seen the 20 minute movie – good job!
    By the way, your controller is your intellectual property. NO-ONE should think they have the right to ask you for specifics of your design and you have no obligation to give out anything. These people have obviously never worked to produce something that puts the food on their table. I would never give out proprietory information on the systems that we build.
    A question. I am building an electric car. I want to use regenerative braking (somehow I thought that your controller did this). I will be using a 1K Zilla. Is there really an alternator that can put out enough amps at the right voltage to give me realistic braking?
    On the three phase side, I wish we could scale up the 3 phase controllers used in the radio controlled model airplane business. They are now running close to 100 amps, possibly more.
    Thanks for what you are doing.
    Peter Fynn

  14. on 21 May 2007 at 5:43 am Mike Durller


    Please do not let the trolls you have posted get you down.

    As an electrical engineer, and one who has worked with IGBTs on much lower power applications, I know good engineering and dedication when I see it in the power arena.

    My hat is off to you, please continue to serve the EV community. You are making a large contribution, even if some may have you question that at times. The vast majority of us are grateful and impressed at your abilities to save so much green house gas from the environment, and allow others fun doing it besides! I wish you the best of luck in your 3 phase adventure, and with the same fantastic success you have had in your DC controllers.

    “Great spirits have often encountered violent opposition from weak minds.” – A.E.

  15. on 12 Jun 2007 at 9:32 am Lon Hull

    As a new guy to the EV world and an old hand in the automotive customization and fabrication industry, I have to offer kudos to you, Otmar, for building a world-class product and standing up for your intellectual property rights.

    We should all do what we can to get more EVs on the street (and you’re part of the solution, not the problem), and I love the fact that EVers are much like the Linux community, but sharing computer code is very different from working with expensive components upon which vehicle safety and reliability depend.

    I’m generous with my friends, but I’m also very protective of the things I spend hours, weeks, and years building. I never flinched when I saw the price page for Zilla controllers, and I’d bet money that you too long for the day when the industry develops enough scale to drive down component cost.

  16. on 12 Jun 2007 at 9:56 am Marty Hewes

    Dude, raise the price, ignore the unrealistic, idealistic trolls. These socialists think you should give away your intellectual property with no compensation for your time and effort. I bet they are the same people who think all music should be downloadable for free and musicians should work for nothing so they don’t have to spend their money. What a load of selfish crap!

    Idealism is amusing, but we’ve all got bills to pay, and only so many hours to sell to the highest bidder to pay those bills before we run out of hours. If your time is worth $X a year plus medical working for someone else, then you should make that providing such a great service as an EV hardware provider. The USA is not socialist. As long as you can do that and not price the product more than it’s worth, you earned it. That’s what funds product development!

    I’m a small business owner. I set my prices so I can pay for medical insurance, pay myself and family a decent wage, and get a better return on the considerable inventory cash than I would in a mutual fund. It’s only fair. Sure I could make a little more working for the man, but it’s worth something to me to be in control. But that’s your call, not someone elses.

    I ordered a Zilla 1K because, with the reputation it’s got, it’s a bargain. I would have paid more. Personally, I don’t want you to make anything less than a decent profit on it. I don’t need charity, and building an EV is not something the underpriveledged generally do :).

    I think you’d be as silly to give away your intellectual property as you would be to give away your 914. Both are your hard earned assets.

    Now, having vented :)…

    I’ve got a question. Does having battery volts way higher than motor volts at low RPM cause excess instantaneous current draw in the power stage during on time, causing protection current limiting of the devices? Or is only average current significant, so it doesn’t matter? I’m just wondering if having greater voltage than necessary could be counter productive due to the mismatch.

    In other words, would high battery volts and the resultant short on time at high draw limit watts to the motor because the devices are protecting themselves?

  17. on 28 Sep 2007 at 12:47 pm Rick Covert


    Some people just want something for nothing. I have run my own business too in software support. A customer once wanted to pay me in 3 installments. He owed me alot of money for my services and I naively consented. He never paid the 2 remaining installments. People like that think nothing of buying a “cheap” product that was produced under sweatshop labor under duress in some developing nation.

    Anyway on to my question. I am an amateur radio operator and plan to operate a radio in an EV conversion project (A Chevy S-10 Truck conversion). I like your controllers, I’m particulary interested in the Z1K Zilla unit, because they integrate well with the existing dashboard gauges. I would like to use as little OEM gauges as possible. I find the features and durability to be very impressive too. Does your controller generate high levels of RF noise in the 3.0 – 30 MHz or 144 to 148 MHz range? Also does the use of a two way radio in the 3.0 MHz to 30.0 MHz or 144 to 148 MHz range interfere with the controller? Mind you I would probably be using 50 to 100 watts of transmitter power in the 3.0 MHz to 30.00 range and up to 50 watts of transmitter power in the 144 MHz to 148 MHz range.

  18. on 07 Oct 2007 at 3:39 pm Rick Beaver

    Otmar, as a small business owner I do understand the day to day running of a business. I do also understand the balance sheet. We are not in this for our health. You seem to have a great product. I am in the same boat, I get paid more for what I know then what I do. We also get paid for the stress of running a business. So why give out any information? You spent the money and the time to develop the Zilla Controller. It’s worth what you can get out of it. I will be buying one later this month. Hey just like anything else, it cost to get the best. Good job and keep doing your R&D. Oh yes that cost money as well.

  19. on 21 Jan 2008 at 8:45 pm Otmar

    This reply is very late since comments have been getting lost in spam for many months. I’m sorry about that. I think I dug all the real comments out of the pile.

    First I would like to thank you all for your support. I don’t need that much money to live, and by now have investments that help pay the bills, but it is true that I should probably pay myself more. I certainly could earn much more with a regualar job. I just don’t want it to be even more expensive to convert a car to electric.

    Peter, I do occasionally have a look at the RC controller progress. They are rather low voltage and so have different challenges than we do, but I’m sure there are things to be learned there.

    Marty, The power parts are well protected even at high input voltage. This, of course, is one of the challenges of building a high voltage controller. The inductance of the motor limits the rate of change of current when the switches turn on. My system is set to run on motors as low as 20 uH inductance. Twenty micro Henries is what you get when you run a standard DC motor far into saturation. High input voltage is not the most efficient place to be running, I see yet another FAQ answer that I need to write. 🙂

    Rick C, I’ve never heard of any EMI from outside affecting the Zilla itself, only the Precharge sense wires at times from the Zilla’s own noise. It’s pretty rugged.
    As for it producing EMI, yes it produces a lot. I don’t know the frequency range, but the battery voltage swings fully in under 65 ns at 15.7kHz. So it all depends on the installation. The battery and motor leads turn into antennas and I have yet to see a good shielding job on them. Most people just give up on AM radio and listen to the stronger FM stations.

    Thanks again for all the supporting words. I’ll do my best to insure future blog comments don’t get lost again.

  20. on 05 Feb 2008 at 10:30 am Mark Jarvis

    Otmar –
    Pay yourself more and don’t feel guilty about it. While I don’t own your product, I’ve heard a lot about the Zilla’s reliability and the support you give it. You (and your people) deserve to be rewarded for it.

    We have contract manufacturers that build our product for us. (At my job – not Neurotikart) They use the Quad place machines. You’re right – they’re great – and even better under the guidance of a skilled operator. And I have to admit, I love watching them work. Great job on the reflow oven – I’ve never heard of one so inexpensive!

    If you’re ever in the Washington, DC area, I’d be honored to have you “test drive” Neurotikart 2. It’s not the White Zombie, but it’s still a hoot.

  21. on 06 Feb 2008 at 11:15 pm Otmar

    Thanks for the supportive comments. I’ve been doing more work on the Quad this week and hopefully will learn to utilize the upward looking camera for alignment of fine pitch parts.

    I’d love to drive the Neurotikart 2, it looks like a blast. If I make it to DC, I’ll be knocking on your door!