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Everything posted by EnigmaOne

  1. I'd resort to the lame, "fine wine" remark, and beat you with my cane; but my momma taught me to always respect my elders. ;) ::: fleeing because I still can :::
  2. I went over capacitor input filters with my son around the mid-part of last year, and finally got my hands back on the books I gave him. I thought a couple of scans from the chapter on diode circuits might be of some help--either here, or in the future. (It makes a decent-enough reference sheet for one's notebook on such things.)
  3. ::: cough ::: What dust? >hack-choke<
  4. ::: Slapping my forehead and laughing ::: Yup. Gotta pick up some more, now that I've been reminded what I'm looking for. ;)
  5. Definitely not that old! :D Some of my favorite vintage equipment definitley dates back to the 30's and 40's; which gave me exposure to the engineering of that era. ...and I certainly forgot about DC switches arcing too.
  6. This is an old (dates back to some time in the 1930's) technique of quenching switch contacts to protect them from arcing, pitting and poor service life. Most generally, I've seen 0.1uF, ceramic disc capacitors used across the contacts of 120VAC power switches, with working voltage ratings from 250V to 1000V; which leads me to believe that anything over the peak voltage of the switched circuit will work just fine.
  7. My apologies. I had intended to go with a Lab curiculum sheet that I had open on one desktop, and got myself mixed up when I was referencing the Fairchild DS file on another desktop. At any rate, the attached schematic calls for the addition of a voltage divider (R4 and R5) to select the potential at Vcont (5). Multiple voltage dividers can be added and selected with a switch. The formulas are fast-n-loose derivations from manufacturer's data (done while I was cooking dinner and taking care of a sick six year-old), so sanity-check things before you put anything on copper-clad or perf board. With 5 kids left in the house, it's a wonder I get anything done. :P
  8. To the issue of powering devices "for free"--because that's really what's being said, here--it can and has been done in the past. My, now dearly departed, high school electronics teacher (don't ask me how long ago that was) said that he personally knew a man he served in the Navy with, who happened to live out in the South West desert area of the USA (I'm remembering that he told us that it was in the Nevada Desert, but it's been so long ago now). Seems this guy dug two trenches directly under the power lines that ran across his (very sizable) property. He joined the trenches with a connecting trench, and placed a very long loop of insulated cable into the hide away and covered the whole thing up. He connected this newly constructed secondary winding, of what amounts to a large transformer, to his house wiring and got the power to run his deep well pump, lighting and appliances for free--for what we were told was something in excess of 15 years. The utility folks eventually came 'round investigating the source of fluctuating power losses, that had previously defied explanation, but had been narrowed-down to the span of high tension wires crossing his property. He was discovered, given amnesty (because there were, at that time, no laws against what he did), given a free utility transformer and drop, and a job with the company--finding people who were cheating the utility provider (exactly what he had been doing). He had his utility charges deducted from his pay check. Now...the "event"--as related to us--took place sometime back in the mid-to-late-1940's; and could be nothing more than a good story to tell a bunch of high school kids in freshman-year electronics class...and every ex-Navy guy I've ever known could tell some whoppers. BUT, I did and do know enough about this teacher to believe that if there is such a thing as being honest to a fault, this man was exactly that. It would be a departure from his "norm" to tell us a lie like that, but I'll leave that one up to you to believe or disbelieve. In that scenario, it is technically possible (given certain power line configurations), but illegal in just about every jurisdiction I can think of. Being close to a high power radio transmitter antenna? Well... #1 - I'd have some health concerns about living in that kind of environment for an appreciable length of time. #2 - You could probably parasitically capture enough power to do something useful with if you converted the received signal to DC and stored it in the usual way. #3 - It's probably also illegal, although I'd love to see a radio station try to prosecute somebody for doing just that. Anyway...that's just me, chiming in on the subject.
  9. Firstly, let me say that I admire your enthusiasm, as well as choice of Operating Systems. Here are a couple of references that I consider very valuable for anyone wanting to learn about electronics: http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html and http://www.ibiblio.org/obp/electricCircuits/ Having been involved with the electronics field since 1968, allow me to point out that your personal success in learning what you want to know about electronics is heavily dependent upon your math skills, and your personal dedication in taking the time to learn the material fully. Without taking shortcuts, it could take you a couple of years to learn the skills you need to achieve the goals you have stated, or it could take you quite a bit longer than 5 years. I will mention that I was self-taught for my first 12 (or more) years of dealing with electronics. I learned more (and more completely) by taking university electrical engineering courses, and follow-up courses in applied electronics technology. Start out by reading through the 6 books found at the second link, above (or at http://www.allaboutcircuits.com/ ), and consult with the academic institutions in your area to discover what courses they offer that can help you achieve your goals. Best of luck to you.
  10. We used to use a chemical--that I cannot, for the life of me, remember the name of now--to clean off oxide residue from soldering irons, before they started cladding the tips. It worked well on the clad iron tips as well, IIRC. I can say that I've seen Radio Shack # 64-020, and another item: from here: http://www.dt.com.au/category.php?pagefrom=ELECT:TOOLS&cat=ELECT:TOOLS:SAIDS that you might find helpful for problems like this in the future.
  11. Page 8 (Heading #4) of the attached PDF should help you out a bit. NE-555.pdf
  12. If you're talking about digital ICs then you'd have the advantage of wider operating voltage ranges, greater noise immunity (as compared to TTL), and lower power consumption. I really don't know if, given the types of circuits you build, those characteristics would be of any benefit. Some folks find designing with CMOS ICs to be problematic, and still prefer working with TTL devices--but I've met very few of those. I'm still not sure what kind of devices you're talking about, because 'CMOS' (Complimentary Metal-Oxide Semiconductor), per se, is a device construction style/technique/process/method (whatever is most meaningful to you) for a wide range of devices. Your question is roughly analogous to asking, after returning from the auto showroom, if you should buy a uni-body car; to which I would reply, "What kind of car do you need?"
  13. I wish I could claim specific knowledge but, for some reason, I have a growing interest in making some sort of space-efficient exposure drawer for things like litho film and pc boards. If I come up with something interesting, I'll certainly share my findings.
  14. Just an FYI: Some of the white LEDs do have a certain amount of UV emission (obviously, not the RGB units). You can, in fact, buy UV LEDs, though they aren't what I'd call inexpensive at this time.
  15. Far be it for me to suggest such a change! ;) Sorry. In the past, I changed distros almost as often as I changed my socks--finally settled on LFS and Mepis as my favorites--so I instinctively go for distro changing/dual-booting to get over a temporary obstacle. You did push me into playing with gEDA for the past few days, and I think I've found a new favorite editor. I can finally dump my Orcad/DOS emulator combo, import all my custom symbol files and go strictly with gEDA on current/future projects. It certainly is worth the hassle of getting the dependencies lined-up and compiled; although, I never would have believed anyone if--before seeing gEDA--they had said the same thing to me. Maybe a dual-boot (Slack/Debian) set-up is in your future? ;) Anyways, thanks for mentioning the proggie. I now have a symlink to it on my DT.
  16. I have never heard of that happening before...and I can't imagine why the cable TV guy didn't have these kinds of standard equipment, which doesn't even require stripping the cable--just screw them in: http://www.ceitron.com/video/couplers.html That guy seriously didn't have a clue.
  17. These are what I'm using: http://www.pomonaelectronics.com/pdf/d6702_003.pdf http://www.pomonaelectronics.com/pdf/d_ai_5079_2_01.pdf http://www.pomonaelectronics.com/pdf/d5348_1_01.pdf I see now that the connector purchased was a 50-ohm connector. :P It won't hurt for 4 or 5 intervening connections, but they do have a cumulative effect; so, if you're going for standard TV and best-practices, or a more complex HDTV setup, you'd want to go with the 75-ohm connectors.
  18. A CMOS what? Can you provide an example of what you're talking about?
  19. ::: snicker ::: Then again, MP, a supposed organization proposing to conduct business using a Yahoo e-mail address isn't worth my consideration.
  20. No. I can't see a rational reason for the existence of the "standard cable TV" connector pair. It's a very cheap and poorly thought-out implementation for any consumer electronics device. I replace all 73/75 ohm "F" connectors with BNCs, since that simply makes it much easier to make and break connections, and the connection quality is much better. :D Of course, having a box of male & female BNCs, that I would otherwise have no use for, in the garage, helps. ;)
  21. You will probably find this set of lecture notes to be helpful in understanding how to create a mod-n counter. (Starting with slide #13.) These may help you as well: http://alldatasheet.com/datasheet-pdf/pdf/FAIRCHILD/74LS74.html http://www.alldatasheet.com/datasheet-pdf/pdf/MOTOROLA/74LS93.html http://www.alldatasheet.com/datasheet-pdf/pdf/FAIRCHILD/74LS32.html http://www.alldatasheet.com/datasheet-pdf/pdf/FAIRCHILD/74LS00.html You should be able to find examples of data-latching circuits at discovercircuits.com (any frequency counter, tachometer or speedometer schematic would present the applied data latch concept); but it's more important to understand the various techniques for data latching than it is to merely copy a given circuit example.
  22. hmmmmm....definitely good potential for a robotic lawn mower. I'd use a buried loop, driven with a 1KHz to 5KHz signal as an invisible border. You could use low-voltage, direct-bury sprinkler control cable, and wire the multiple conductors to obtain a multi-turn coil very easily. Use 3 inductive pickups, at 120 degree intervals on the bottom edge of a circular robotic chassis. Amplify the signal from each inductive pickup and bandpass-filter the amplifier output to obtain only the frequency that you're interested in. Feed the filtered output to a comparator and use the three comparator outputs as border proximity inputs to your microcontroller. From that point, it's merely a matter of the same type of programming that you would do for a simple obstacle avoidance routine.
  23. I've always used a fine-grade hacksaw blade, followed up with a couple passes across the face of a 400-grit belt sander. Works like a charm.
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