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Paper Robot

I actually found a tidbit of useful information in PopSci from November. They had a link to a paper robot. While the instructions and materials provided in PopSci were probably OK for manual use, my wife got a CriCut last year, and this seemed a perfect place to try it. After playing around with the PopSci information for a while, I emailed them and received a response that they didn't have anything better than JPEG files for the cut/fold maps. Fortunately, they provided some information that allowed me to find Ankur Mehta, an MIT fellow who produced the originals. He was able to send me updated version in PDF, SVG, and DXF.

The SVG version imported into CriCut Design Space, and I'm cutting and scoring the design as I type this. It looks like it will work, but there are quite a few "artifacts" from the SVG creation process that make it less than ideal. In particular, the "wheels" which look like circles are actually a large number of segments designed to approximate a circle. This means that the CriCut will cut each segment individually instead of as a single continuous cut.

I've downloaded Inkscape, and I'll try to see if I can clean up the SVG, though I don't know if SVG can represent circles directly, or even if it can link multiple vectors together into a single "construct".


So, one of our family Christmas presents this year was a Wii, along with the Wii Fit, which Karen and I had tried out at her parents house a month or two ago, when I set it up for them. I set it up on the TV in the basement, in the room that I just re-finished. Turns out this isn't exactly ideal, since the ceilings are less than 7 feet down there. This means that I can't do some of the yoga and strength exercises, as my hands would have to go through the ceiling.
All that aside, though, I've gotten up before 6 the last two mornings in order to do a workout. On Monday I didn't give it any real thought, and just went through most of the available options. This morning I figured it'd be better to start with a warmup, then do some strength exercises, then do balance and yoga. At least, I think that's what I did, it was pretty early. I improved on almost everything I did. I was completely incapable of doing regular pushups this morning, so I cheated and did those on my knees (yesterday they were no problem, so clearly those muscles need a bit of time to recover). It's kind of nice that I don't have to write down any of the exercises I do, since the computer, err, I mean, video game keeps track of it all for me.

Escort Service?

So, driving to work this morning, I was passed by a truck with a sign painted on the side. The sign read "Truck Escort Service", which just begs for further comments. The best we could think up this morning was "They must really move fast," and "They go the extra mile." There must be more, though....

Laminate Flooring

So, I installed my first laminate floor a couple of weekends ago. In case it's unclear, these are the composite materials that look like hard wood flooring, but just have a veneer and a protective coating on the top. The flooring is an Amber Oak, which we picked up from Sams Club. The floor looks quite nice, and has a pretty authentic look. It wasn't too hard to put together, mostly "folding" down into the previous piece. There was quite a lot of hammering and smacking with a dead blow mallet and a 2x4 to protect the piece. Even being careful, I managed to break a few pieces, especially on the "tongue" side, where the top surface is < 1/8" thick. We put down around 400 square feet of flooring in just over one day, although much of it was one large room, and didn't require any fancy cuts. Progress slowed significantly when we had to deal with doorways, transitions, and closets.

I started out cutting everything with a 7 1/4" plywood blade on a handheld circular saw. This worked well, until it started to rain, and we had to move into the garage. Because of a lack of space in there, I switched to using my 10" Craftsman Table Saw. By the end of the job, the blade on the circular saw was clearly dull beyond use (all of the saw blade tips were rounded). Just yesterday, I tried to use my table saw to cut some boards at 45 degrees, so that I could build a square box. I had a devil of a time with it, I suspect because the saw blade is very very dull. The carbide tips are all intact, but it doesn't cut worth anything. Apparently the surface on the laminate is hard enough to dull any cutting tool. Alas, this means I need to have that blade sharpened, or buy a new one, as I can't make the kind of precise cuts that I need in order to make furniture without a sharp blade.

All things considered, I think I prefer installing full thickness (3/4") hardwood flooring over the laminate. With a pneumatic nailer, it's pretty quick to install, and a LOT harder to break or damage than this stuff. We'll see how the finish holds up on this compared with the prefinished hardwood.

Pondering Motor Vehicle Engines

So, being an engineer, with some mechanical aptitude (not necessarily as in a car mechanic, just for building things) I have been tinkering with the motor vehicles that are available to me lately.
The car that I'm driving here in West Virginia is a 2000 Chrysler Voyager. Not a bad car, though being 6" longer would help quite a bit sometimes. This car has a three liter (3.0l) one hundred forty horse power (140hp) engine. OK, so what, right? Well, the other car that I have is a 1995 Eagle Vision TSI. This car has a three point six liter (3.6l) two hundred fifteen horse power engine (215hp). This means that for a 20% increase in engine displacement (3.0l * 120% = 3.6l) the engine achieves more than a 50% increase (140hp * 150% = 210hp) in output horse power. Clearly the relationship here is vastly non-linear. Should it be? I don't know. All I'm sure of is that the Vision is a lot more fun to drive, and gets the same or better gas mileage than the Voyager.

Drill Battery Rebuild, part 2

I managed to solder up the first battery pack about a week and a half ago. Even with the solder tabs it was quite annoying. It might have been a bit better if I'd had a good iron, but a 25W, non temperature controlled thing wasn't the right tool for the job. However, I did get it all put back together, and got it to fit inside the case. I closed it up, drained the batteries, and put them on to charge again. It seems to do quite well so far, although it doesn't have very much power compared with the 19V system that Karen's father brought up the other day. Since it does seem to be working well enough, I'll probably go ahead and re-build the other 13.2V battery, and maybe order another set of cells to re-build the two 10.8V craftsman's that we've got here, so that I can send those to work with Karen, so that she'll have something to use there.

Using that 19V Craftsman really makes me want to get a set of the Milwaukee tools. The Craftsman tools work fine, but if I were running the saw any more than a tiny bit, the charger and the batteries wouldn't be able to keep up with me. The drill, however, runs nearly forever on a charge.

Drill Battery Replacement

Several days ago, both of the batteries for my "13.2V" craftsman cordless driver/drill went out on me, literally simultaneously. I suspect this is as a result of the hard work I had just put them through. So, I had to finish that job using a corded black and decker we have. It's got plenty of torgue, but is much too fast for driving, and has no clutch at all, so it's very easy to overdrive everything. When I was tested the batteries to see if they had any charge, I noticed that, gasp, these packs looked like they were held together with screws. The voltage was quite low, so I pulled the screws to see if they really had made it user serviceable, and they had. Hooray!
I got online and priced both replacement batteries ($50+ shipping, ouch), and individiual sub-C cells, which were also expensive. In the end, I found an auction from Powerizer/batteryspace.com on ebay that ran me $37 with shipping, to get me all the cells I'd need for both packs, along with 2 spares, and pre-soldered with tabs. The cells are "not shipped fully charged", but after testing all of them, they read between 1.28V and 1.31V OC, with the exception of one cell which was at 1.20V. Those all seem plenty charged enough for me, so I'm going to go ahead and build the packs with them, without doing any testing or charging of the cells at all. Once the packs are built, I'll put them in the charger for a full charge, then drain them, then charge again, and call it good. I'm sure I can get that much done this week.


At the moment, I'm looking at buying a desktop system. It's relatively easy for me to compare PCs, but much harder for me to compare LCD monitors.

I've been using a widescreen monitor on my convertible tablet PC for a while now, and I've definitely decided that I want to go widescreen. The screen on this does a maximum resolution 1280x768, which is somewhere between 16:9 and 16:10. The screen is supposedly 14" on the diagonal, and I'll go with that for calculations. If I calculate the Width and Height using the following two equations
W^2 + H^2 = 14^2
W / H = 1280/768
I can find that the screen dimensions are W = 12.0" and H = 7.2". If I use that along with the screen resolution, I get that the horizontal DPI is 106.7, and the vertical DPI is 106.6, about the same. Now, this is a nice screen, but I certainly wouldn't complain about getting more pixels in the same space. So far, I haven't found anything.

For reference, here's some info on 17" widescreen displays, calculated the same way, using 1440x900 as the resolution (since that's the only resolution I can find):
W = 14.4"
H = 9.0"
Hdpi = 99.86
Vdpi = 99.89

Most of the 19" displays I've found are even worse, in that they'll only do the same resolution:
W = 16.1"
H = 10.0"
Hdpi = 89.39
Vdpi = 89.37

I found one 19" display that is capable of 1680x1050, and it's specifications list a height and width matching my calculations for 19" displays above (as do my calculations using this resolution). It comes out much better
Hdpi = 104.3
Vdpi = 104.3

Still not as good as my laptop. So, one suggested that 19" wasn't a very popular size anymore, though from looking at sites like tigerdirect and newegg, it seems to be the most popular size. So I checked out some larger displays.

20" displays seems to be 1680x1050:
W = 17.0"
H = 10.6"
Hdpi = 99.06
Vdpi = 99.15

22" displays are fairly horrid (almost as bad as normal 19"), with a max resolution of 1680x1050:
W = 18.7"
H = 11.7"
Hdpi = 90.03
Vdpi = 90.05

24" displays are the new small premium size, let's see how they compare. 1920x1200 resolution yeilds:
W = 20.4"
H = 12.7"
Hdpi = 94.35
Vdpi = 94.35

Still well below my laptop display.

Just for S&G, here's how a 30" display compares, with a resolution of 2560x1600"
H = 25.4"
W = 15.9"
Hdpi = 100.6
Vdpi = 100.6

Given that there's still nothing out there that compares with the 15" 1600x1200 display I had on a notebook 5 years ago, I'm quite disappointed. I was really hoping that we would have some 150 dpi displays on the market by now. I'm thankful that we've gotten over 17" monitors that couldn't adequately display anything more than 1024x768 (a whopping 75 dpi).

I can't think of any more research to do on the topic, so it looks like I'll be going with this viewsonic.

Aside from having the highest dpi, it's also got a 1000:1 static contrast ratio (up to 3000:1 dynamic), 2ms response time, 300cd/m^2 brightness, and DVI-D and VGA inputs. I'm not so sure about the stand on it, as I really like the Dell stands that let you rotate the monitor. If it comes down to it, I can probably fabricate something that will work, and paint it a nice matte black. Oh yeah, Newegg and Tigerdirect each have it for $219.99, which isn't too crazy expensive.

Senior Project

I spent most of the day working on my senior project. Mostly I worked in OrCAD, putting together the parts for my project, then creating a 4-page schematic that is everything that will be on the board. That was quite an ordeal, but it's done now. I also downloaded and installed a trial version of PADS, from mentor graphics. I don't have any idea how to set up the pads for the ICs themselves, or start on getting the rest of the layout done. Hopefully Jon will be able to help me out with that tomorrow.

Senior Project Status

This week we have a status report due, along with our test plan. I just completed my status report, so here's a summary.
The latest block diagram is at http://www.flickr.com/photos/33604751@N00/501433865/
It's got just a few additions. Most importantly are the buffers between my 10.245MHz oscillator and the two mixers. I used two separate buffers in order to make sure that I didn't get any crossover distortion from the two mixers. These buffers aren't yet designed, but since the voltage swing produced by my oscillator is fairly good. I just need to be able to drive quite a bit more power into the load.
I think that my active filter will end up being a fourth order (40db/decade on each side) butterworth filter. It will probably use a sallen-key filter topology, since the amount of documentation on this is tremendous (I have four books in front of me, all of which discuss sallen-key). I suspect that I will simply do a low-pass followed by a high pass, rather than doing a bandpass filter. This will mean that I need to do two designs, but that's not much of an obstacle. The center frequency is the geometric mean of the two cutoff frequencies, and I want a bandwidth of 50kHz. My calculations show that my lower cuttoff frequency will be 430.686kHz, which we'll go ahead and call 430kHz for calculations. Similarly, the upper comes out to 480.686kHz, which we can round to 481kHz. I might need to shift these frequencies slightly, just to make sure that I don't have too much attenuation at the corners, giving me less than my specified 50kHz bandwidth. I'll hopefully finish the filter design tomorrow morning when I come in to work on things.
I found the standard component values for my passive filter yesterday. I did some simulations, and it looks like it will work really well, though the values I can get will shift things so that 10.7MHz is slightly "down" one of the ripples, rather than at the peak. I don't think this will be an issue.
Rather than doing a full detailed design on things tomorrow, what I think I'll do is draw out the topologies for the filter and the buffers. Once that's done, I can spend the rest of the day laying out my board. If I had known how National Semiconductor sent samples (that is, including development boards), I would certainly have designed my project around using their products. I would just have connected all of the various pieces together using short lengths of SMA cable. As it is, I'm going to lay out my design on a board, and have to get it ordered this week. I'm going to lay out the board from the output of the LNA, which will be an SNA connector, all the way through my active filter. The LO will be on there, along with all of the VCOs and mixers. Both image rejection filters, and the LO buffers will be on the board. The output of the first stage will go to an SMA connector, , which I'll then couple into my VGA. I got a devel board with the VGA, which has spots to put the SMA connectors, so I'm going to just build and test that separately from everything else. Then that will get coupled back onto my board, and fed into the first up-converting mixer. Signals will then flow through the board a bit, and finally end up at another SMA connector, feeding out to my RF power amplifier. If I'm quick and brilliant this week, I MIGHT try to put in some transmission line LC filters before feeding things out to the power amp. I think this would probably help my power output spectrum a LOT, and might even be necessary (uh-oh).
The reason that I'm not going to try to put the VGA onto my board is that I haven't done any development or testing on it yet. I'd really like to do that, and be able to do this as a complete integrated solution, but I feel that I need to get my board laid out and ordered ASAP. Once this is done, and I finalize the specs for my filter, buffers, and the controls on my VCOs, then I'll have some time to mess around with the AGC, and get it working separately from everything else.
Ack, that sure sounds like a LOT of work! I'm coming in early tomorrow to start cranking on this stuff.