Stories of Coincidental Electricity

The annual Tanner Electronics Robot Show was on Saturday, April 14. The DPRG held their annual robot talent contest concurrently. So, not suprisingly, I was planning on working late the preceding Friday to get my new little robot, Robozoa, into shape. This mostly involved finishing some hardware-related things like wiring from the H-Bridges to the motors and from the motor encoders to the microcontroller. This sort of work is better done at the DPRG Lab where there are plenty of tools and test equipment to make it easy.

The weather prediction was for rain in the evening, so my plan was to head up to the DPRG immediately after work. Not suprisingly, a last-minute work-related emergency held me up for a couple of hours. By the time I was finally able to leave, a torrential rain had started. When a break in the rain materialized, I ran out to my car; only to get a phone call before I was out of the parking lot. The call was from Susan, who was holed up at home in a bathroom with the three cats because the TV had just announced a tornado was headed her way. She said the tornado watch area extended to the downtown area where I was, so I decided I’d be better off inside the office than in my car until things calmed down.

I ran back through the now heavy rain into the office. As I dried off, I clicked up a few weather radar sites. Sure enough, there were some nasty looking thunderstorms headed my way. They passed over Irving, where Susan was, without any serious damage resulting (it’s now unclear whether the reported tornado really touched down or not). The worst of storms were now north of Dallas in the Garland area, where the DPRG Lab is located. I decided to settle in and do what work I could on the robot at the office. I finally left about 1am by which time the rain had stopped. I was a little annoyed that this series of events had kept me from making it to the DPRG where I could have worked more efficiently.

The next morning, I showed up at the Tanner’s event. The previous night’s storm had brought with it a freak, one-day cold front. Despite the cold, a fair number of humans and robots showed up to participate. But, more interestingly, several people said they’d seen the DPRG’s building in Garland on the news. There were firetrucks in the parking lot. Apparently it was hit by lightning. Eric Sumner, Ed Paradis, and I decided to drive up to Garland and check out the damage.

From what we could tell, the lightning hit the transformer immediately behind the DPRG building. It largely destroyed the power line between the transformer and the building, reducing it to a series of short fragments. The power meter was completely destroyed. The charred metal casing of the meter was still on the wall, surrounded by blackened bricks. The transparent housing and meter electronics, or the remains of them, were found on the ground. The meter had contained several boards with surface mount components. The lightning blast had desoldered all the components and completely vaporized many of them. Inside the building, the main breaker box was also a charred mess but it appears the breakers vaporized so quickly that it limited the damage to the downstream breaker boxes.

By Tuesday power had been restored and we were able to evaluate the damage. Remarkably, the only losses discovered were a single surge protector and one very old dot matrix printer. Aside from those two casualties, test equipment, networking gear, computers, all seemed to have survived no worse for the wear. All thing considered, I’m glad I wasn’t around Friday night when it hit.

Cats, Caps, and Contests

Ultracap Update

After prototyping a cell-balancing circuit for my robot power supply based on Maxwell 350F Ultracaps, I discovered the original choice of the TI TLC25L4CN low-voltage op-amp was not a good one. The little chip just couldn’t deliver enough current to balance the cap voltages in any reasonable amount of time. The peak output of the prototype was about 4 ma. So after spending a couple of hours searching for an op-amp that could operate at low voltage and put out a substantial amount current, I came up with the TI TLV4112IP high-output-drive op-amp. At last week’s RBNO, I built a second prototype and… it works! The new op-amp outputs up to 300 ma easily. Using the test circuit, I set it up with one Ultracap at 1v and the other at 2v. In little over a minute, the system balanced with both caps at about 1.6v. Next Tuesday, I’ll put together a more complete prototype with four Ultracaps and three cell balancers.

The cell-balancer has also proven to be a good way of trying out the GPL Electronic Design Automation (GEDA) package. I’ve been using the schematic capture program gschem primarily (screenshots) and have been asking lots of stupid, new-user type questions on the mailing list. They’ve been very patient with me so far and I’m begining to get the hang of it. It turns out good-looking schematics. Once I finalize the power supply, I’ll post a link to the GEDA files for anyone who might want them.

Cats in the garage

The abandoned mother cat and two kittens we brought home a few weeks ago are still with us. We know a lot more about them now. The kittens were much younger than we first thought. We’ll probably hang on to them until the kittens are a bit older. Susan has settled on names. The half-siamese mother cat is Sophie, the black kitten with the missing toe is Zippy (though she insists on spelling it “zippie”), and the tailless calico kitten is Callie. No luck finding a home for any of them yet. Callie is probably too emotionally disturbed to make a good pet but we have located a group called Barn Cats International that assists with finding homes for problem cats on farms and ranches where they can live with minimal contact with humans. Hopefully we’ll be able to find good homes for the other two. If anyone in the Dallas/Ft. Worth area needs a cat, let me know!

Nigritude Ultramarine contest outcome

The contest ended on July 8th. Thanks to everyone who linked to my site, especially, Bram. His link resulted in more hits on my site during the contest period than anything except Google itself. Feel free to remove those links now. I’ll probably leave the page up until the domain expires. I ended up in position 6 in the final results. The winner was a blogger who apparently won primarily through old fashioned Google bombing. Oh well, my site received a sort of honorable mention prize, the Judge’s Choice Award. My prize is one of those teeny, tiny “James Bond Stealth digital cameras” like you see on ThinkGeek. I’ll post a photo as soon as I get it talking to my Linux box (it only comes with Windows software but it has a USB cable so I’m hoping I can just mount it like a little USB drive).

We’ve been pretty busy at the office doing website design jobs. The lease on our office space is up soon and we’re deciding whether to stay put or move to new space. Even if we move, we’ll stay in Dallas and probably in the same general area.

DPRG and Robot News

At the DPRG RBNO last night, I worked out the basic design for my robot power supply with the help of a few other DPRG folks. The plan is to use 4 of the Maxwell 350F caps to store power from solar cells. (Someone was asking about the cost – the single unit price of the caps is $25). One hitch to using multiple ultracaps is that you have to dynamically balance the voltage between caps. To do this you need a simple circuit made of an op-amp and a couple of resisters. You need one balancer at each connection between caps so, for four caps in series, you need three balancers. John Drummond helped me track down the TLC25L4CN low-voltage op-amp. It works on as little as 1.4v (which equates to .7v per cap). That gives me an operating range of 2.5v to .7v per cap or 10v to 2.8v for the entire power supply. Once I get the parts and test it, I’ll post a schematic.

In other DPRG news, the DPRG mailing list upgrades have been completed. The list now has better spam and virus filters, email address munging, and a shiny new searchable list archive going all the way back to 1997.

Robots and Robotron

I’m finally within sight of being mostly caught up on a lot of the work around here. Susan and I managed to find time to make two DSO performances in January. I might even have enough free time to keep my weblog up to date or work on a few non-work-related projects during February.

Work on the DPRG‘s non-profit status continues. We received our certificate of incorporation from the State of Texas this month. The next step is filing the 501(c)3 application with the IRS. The Tuesday night RBNO meetings at the DPRG World Headquarters (aka the “warehouse”) continue to grow in popularity. We now have two live webcams and an IRC channel during the RBNO.

I had to squeeze in a little time during January to open up the Robotron: 2084 cabinet and tune up the joysticks. A fellow VAPS member has challenged me to a game. This is the first time in 15 years or so I’ll be playing against another expert level player. In the 80’s I don’t think anyone could beat me – but I’m a bit rusty these days, so it’ll be interesting to see what happens.

I’m thinking about updating the Robotron logic board to the slightly newer blue ROMs from the yellow/orange ROMs I currently use. At one time this would have been a simple matter of going to any of dozens of Internet ftp or web sites that offered the ROM images for download and then burning a new set of EPROMs. But it appears there has been some sort of crack-down on arcade game ROM images online. Several fellow collectors emailed me the ROM images but it’s sad that this has gotten so much harder than it used to be.