Odd Lots
- The xenon flash problem with the Raspbrry Pi 2 board has been explained reasonably well on the Foundation site, by Liz Upton. Key seems to be that U16 is not a typical SMT chip encased in black resin, but a naked BGA (Ball Grid Array) chip, which allows light to hit the chip’s silicon directly. HackaDay’s Brian Benchoff says that a cheap green laser pointer will also do it, suggesting that the wavelength of light hitting U16 matters crucially. Hey kids, this is a science fair project: What wavelengths of light trigger photoelectric emission on an exposed silicon die? (Many thanks to Michael Covington for the link.)
- Adafruit has a nice benchmark page for the Raspberry Pi 2, which also provides detailed descriptions of the differences between the new board and the older boards.
- What’s going on in the Martian atmosphere?
- There’s a single SMT chip at the heart of the Baofeng radios I described recently: The RDA1846. I would love to see this on a cape/shield for one of the popular embedded boards, especially the Raspberry Pi. Not quite a true SDR, but mighty close, and I’d guess damned useful for radio tinkering. (Thanks to Bob Fegert for the link.)
- By the way, “Baofeng” and “Pofung” are the same company. It sounds like they were trying to make “Baofeng” easier to pronounce for Westerners, but in truth I don’t think it was much of a problem to being with, and I admit I was confused when I first ran across “Pofung.”
- Norse’s real-time IP attack map is very cool in a War Games sort of way, but it takes some study to figure out what exactly it is that you’re seeing. (Thanks to Pete Albrecht for the link.)
- Here’s a nice collection of homebrew radio projects from Jim McNutt WA6OTP, with pictures and schematics. Fine work!
- An interesting short introduction to the geophysical differences between Earth’s north pole annd south pole.
- More crazy weapons, including but hardly limited to the Panjundrum. I’ve always liked the Triebflugel, which was a great idea until you had to land it, kind of like the XF-85 Goblin.
- That’s not a monkey on that marathon runner’s back. It’s a tomato-dispenser robot. I guess we’re in somebody’s vision of the future. It certainly isn’t mine.
Posted in: Odd Lots.
Tagged: ham radio · hardware · humor · rpi
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I have not looked closely at U16 but it sounds like what is commonly called a COB (Chip-on-Board) that is usually underneath those blobs of black epoxy that every geek has noticed…they forgot the blob ..lol
One fun test to run on the RDA1846 would be to send it the control codes to operate on 6 meters and see if there is both RF output from the chip and good sensitivity to a weak RF input to its receiver section. The chip is certainly able to operate outside the ranges detailed in the spec sheets… one proof of that is the commercial FM band ability it has. Generally, SDR reaches a limit in the upper bound while the lower bound goes nearly to DC..so there is hope for 6 meters on the RDA1846. Replacing the original microcontroller with something that can be programmed and altering the RF output section might result in a 6 meter/144 handie. You would have to wind and encapsulate a custom duckie though.
The cheapo but very capable RDA1846 makes one wonder just what sort of tiny SDR wonder chips the NSA has cooked up in their not-so-secret chip FAB…. and what the heck are they doing with the tech!? I have a few ideas about what they are doing.
If I remember right, “back in the day” I saw an article about making a photodetector out of an old RAM chip with the ceramic cover cracked off… back when RAM chips had two-piece ceramic cases, anyway.
For that matter, when reprogramming my truck’s computer I use ultraviolet light to erase the EPROMs. Eventually even ambient light will eventually do the job, which is why I keep a supply of old 5-1/4″ floppy write-protect tabs…
There was talk in the magazines about taking the top off a to-3 transistor to make it light activated. The catalogs around the same time offered a similar device, but I don’t know if it was issued from the factory that way, or a third party did the mod.
There was an article in Ham Radio for a 6metre synthesizer, and the author had problems with hum. He eventually realized that the diode he was using as a varactor had a clear glass case, and the desk lamp was light modulating it.
Sam Harris’s first article about the parametric amplifier in CQ warned that the hardest part would be getting the varactor (this was the late fifties). He urged anyone wanting to build one to try diodes on hand, which often has been the case later.
RAM was used as an “eye”. Pry off the top (much easier with the ceramic cased ones) and the bits would react to light. Very low pixels. You’d refresh the dynamic ram to get the image.
The Cyclops in Popular Electronics in early 1975 used RAM this way, a “computer eye” to fit into the Altair. The authors went on to form Cromemco”. I can’t remember if they bought RAM intended for this purpose or modified RAM.
Later other projects used ram in this way, but there was definitely a point where RAM was selected and packaged with a window for this purpose. The higher density RAM, the higher the pixel count.
Michael
> What’s going on in the Martian atmosphere
Well, *obviously* it’s Anthropogenic Global Warming. Duh!
You should eschew the evils of electricity and fossil fuels, and heat your home only with carbon-neutral peat and animal dung!
The plumes in the Martian atmosphere are the first sign of the Martian invasion of Earth, of course, and H. G. Wells warned us about it. Maybe if we trick them into eating Activia, the bacteria will get them like it did in War of the Worlds.
…or at least it’ll make them “regular.”