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

I have gotten a few comments posted about the next regolith excavation challenge, and I will address those, and some other issues here...

The 2007 challenge was a little strange. The first prize was $125,000, and that should have been enough to cause a lot of interest. Initially, I heard that over 100 teams expressed the intent to enter, but by the time I entered, only 9 were actually planning to attend, and only 4 showed up at the competition. Cal Poly San Luis Obispo is 30 miles from the contest site, why weren't they there? I can only imagine that they all thought it would be too difficult.

I didn't enter until I determined that I could use a stationary machine, but I expected other teams to have fancy rovers picking up material and dumping it into the collector. I was very surprised when the other three teams all had stationary machines.

Read More...

I generally try to keep politics out of this blog, but I must mention this guy at least once.

No other member of Congress has the integrity, or the consistent voting record of this guy, I am totally impressed. Most of his ideas to repair the United States are a little on the fringe, but this country has been taken to the fringe by a long history of greedy politicians.

Ron Paul can sell himself, he doesn't need my help...

Watch his videos on YouTube, and see if you can find a more qualified candidate for President of the United States.

Part with a few dollars to help his campaign.

Jim

... is publishing an article on Sunday, July 1, about the NASA Centenial Challenge program. They will be focusing on the latest three challenges, including the regolith challenge that I participated in.

A photographer from the magazine spent a day at my house a couple of weeks ago, so I am eagerly waiting to see how it looks, what they said.

Check it out... NY Times Magazine online

Jim