I have switched to WordPress based blog , so all new post will be made there...

I hope you stick with me. The new site should allow more interaction...

Thanks,
Jim

I suspect that most people reading this have some idea of what took place on Saturday, but I will fill in some gaps. I'm still exhausted, but here goes...

Summary:

Nine robots actually competed
No excavator put regolith in the collection box
Only a few even moved out of the corner
Only one dug any material at all

Fortunately for me, the Tornado was in the last two categories, and was awarded the first place trophy. This is an honor, and better recognition than last year, but the $500k would have been nice.

Read More...

However, I have a fantasy that 7/31 will be "hands off", so that makes 24 days...

I am happy with the progress, but still lots to do. Finalizing the drive train, and still looking for the "just right" motors. I am using a conveyor to lift material into a hopper, and stumbled upon a key piece of information that finally led me to an excellent design. Preliminary testing yesterday gives the green light...

I received 500 lbs of JSC-1A in March, and built a 4x8 sand box. It doesn't allow driving around much, but makes a big difference for testing mechanisms. I suspect that others bought some, but I don't know. A five month lead time didn't help matters.

It sounds like everything will start Saturday morning, I'm not hearing about a Friday night mixer like last year. With the quarantine at the start of inspections, it doesn't look like there will be much time for on-site, last minute tweaks.

I was reflecting about the absoluteness of the whole thing while thinking about actual NASA missions. We get one shot; put the machine in the box, hook up the power, say "Go", and hope for the best. It was the same with the early Apollo rockets, some went up, some blew up. I'm sure the engineers were gritting their teeth before launch just like we will be… ;-)

I have been working on the excavator for many months at a somewhat leisurely pace, and am now starting to feel the crunch, as I imagine everyone else is...

The video went well, as most sub-systems are operational. I'm still working on the navigation, and it's going fairly well, however, I still need to examine plan B.

After the registration close date I expected to hear about the remaining teams, but was surprised to hear that 5 more signed up. As with last year, I suspect that some won't make it to the competition, perhaps 50%, but we'll see. I don't know what the refund policy is for those who opt out. Regardless, it will be a busy weekend.

With so many teams involved, it will be fun to see all of the designs. Things have been quiet on the web, as expected, so it will also be interesting to what gets published after the competition.

Be sure to check the FAQ often, or set up an RSS feed to it. I was surprised to see the talk about passive components. Since I hadn't really included any in my design, it made me wonder what I was missing. I have been whining about the ramp being a side effect of an un-filled sand box, but Matt assures me that the design challenge offered by the ramp is something NASA wants specifically addressed. I told him I would stop whining about it now.

I also expressed some concern about voltage drop at the robot power connector, and that due to the long power umbilical this year, it could be a real issue. I suggested using the third contact of the power connector as a sense line for a regulated power supply (perhaps better than last year's) to make sure we actually have 24 VDC delivered to the bot. If others share this concern, please send a message to CSEWI…

I guess that's all for now, the countdown continues…

I haven't written anything here for a long time, my bad, but I don't have much to say about the excavation challenge right this second either...

The next beam power challenge is coming up this Fall, and it's not too far away. I once thought about entering, but I just don't have time for both contests. So, I will give some design secrets away to those who are in the contest, and happen to read this. They might not be new to some, but they are design approaches that I intended to use.

PV panels exhibit some interesting properties regarding the relationship between their voltage and current outputs, and some side-effects because of the way they are built; individual cells wired in series. This means that unless the entire panel is illuminated evenly, you may get only as much as the least illuminated portion, which might be dark, hence zero output.

Here is what I wanted to do.

First, make your own panels from individual cells. Wire them in series, and put a reverse-biased germanium diode across each cell. This way, if a cell is dark, current generated by other cells can pass through instead of being blocked.

Next, wire the cells in long strings to produce 70 - 100 volts, and connect them to a power point tracking (PPT) regulator, which is really a DC-to-DC converter with a constant output voltage. However, there is an important addition. PV cells output their peak power at a certain voltage and current, which is controlled by the load impedance. The true PPT regulator adjusts its input impedance to operate the cells at this point.

The other part of the above design is that even when illuminated poorly, you might still get 20 or 30 volts, for example, and while this won't translate into a lot of POWER, at least you will get something. Whereas, with a 12 volt panel, running at 18 volts fully illuminated, you might get 10 volts when poorly illuminated, and that does nothing for a 12 volt system.

So, in my opinion, these three features can add greater chances of success to beam power challenge teams. It isn't rocket science, just squeezing every watt of power possible out of a PV system.

In summary:

1. Construct panels from strings of cells with reverse diodes across each one.

2. Make the strings long for higher available power.

3. Use a PPT regulator to step-down the high voltage, and operate at maximum power.

Good luck,
Jim