Member #134773

Member Since: May 19, 2010

Country: United States

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I started playing with electronics in the mid-1960s, and with computers shortly after Neil Armstrong took “one small step”. I got a degree in CS in 1980, and started working then as an engineer.

  • An additional thought: If you really want “high power” into a low ohm load, try a lead-acid battery. A quick computation, assuming a fully charged car battery, is that it could put more than 1.1 kiloWatt into a 0.17 ohm load (and keep it up for the better part of an hour), though methinks the coil would not maintain continuity that long… and, of course, if you really want to live dangerously (going for a Darwin Award), there’s 120VAC…

  • Glad I quit smoking the “easy” way – I never started. (FWIW, I avoided the peer pressure in high school by always having a lighter in my pocket. When someone would pull out their cigarettes, I’d pull out my lighter and offer them a light – they almost never noticed that I wasn’t smoking. Then in college, I kept a magnifying glass in my pocket. When outdoors, I’d insist on using it to light their cigarettes – folks quickly learned to not smoke around me!)

    Many years ago, I heard a “recovering” addict from both heroine and nicotine say that nicotine was much harder to kick than heroine. I’ll take his word for that one!

    That sub-ohm measurement is certainly one place where the “Harbor Freight Special” DMM won’t cut the proverbial mustard! I’d not thought about today’s meters being able to “null out” lead resistance, but I’d still rather use a 4-wire measurement to eliminate any potential (pardon the pun) contact resistance.

    One last question: You’re in Colorado; just out of curiosity, anyone up there selling juice with THC?

  • I thought about the modern “sewable electronics” movement last night when a show on “Hidden Dangers in the Edwardian Era” on PBS mentioned that back around 100 years ago there was an “electric tablecloth” that had embedded conductors connected directly to the “mains” power and the user [abusee?] would “plug in” a light fixture at any desired point on the table. Sure glad the modern stuff sticks to stuff in the 3V to 5V region!

  • About “normal” operations on Jan. 16: Banks and the Post Office will be closed for MLK Holiday, though UPS and FedEx will have normal operations.

  • Regarding the “Murican” units for thermal resistance, back in the 70s and 80s, I recall seeing degrees F/W used (or at least quoted) from time to time. Yeah, it does sort of “mix metaphors”, but since W can be gotten at by simply multiplying volts times amps, it is a lot more direct to use watts than to go through the bother of converting to BTU/hr (British Thermal Units per hour). (You still see “BTU/hr” ratings for things like kitchen stoves and furnaces, even though they often forget to specify the “/hr”.)

    Although I recall hearing somewhere that there were proposals for non-metric units for what today we call voltage and current (and others) back in the mid-19th century, they never got any traction. I’ve seen books aimed at “hobbyists” from more than 100 years ago, and they used V and A units, even though they talked about feet and inches. (Interestingly, they talk about wavelengths in terms of meters even back then. IIRC, some of the books actually had appendices explaining how to convert from feet & inches to meters [and cm and mm] and vice-versa.)

  • I can’t resist this pun: The banner at the top of the page says that Friday is “inventory day” – does that mean that this “counts” as the “new product” for this week? ;-)

  • I’m typing this on Jan. 11, 2017, and they’re listed as “in stock”. I happened to notice the date on the schematic is 12/14/16. I’m impressed – I know the complexities of getting a new product out, though the schematic says “REV 10”, it still (likely) means a new PC board, and getting the manufacturing lined up. With all the holidays in there, less than a month is pretty good for a $15 product.

  • And I’d thought that maybe you were going to try for Antiques Roadshow with that old DMM! ;-)

  • More thoughts: A good reason to have the “cheapies” around is that sometimes it is useful to be able to make two (or more) measurements “simultaneously”, for instance, watching both the “input” and the “output” of a circuit, or measuring both the current and the voltage at the same time.

    Also, with the “cheapies”, it’s no big loss if they happen to get destroyed – which is why I keep one of the “Harbor Freight specials” in the car – useful for doing things like checking the battery voltage, or checking continuity on a fuse or lightbulb, etc., but if it “goes for a swim” (or has some other disaster), I haven’t lost a lot.

  • Shawn,

    Great video! Keep up the good work!

    FWIW, about 5 minutes before I went to Sparkfun.com this morning, I realized that last night I’d used a DMM to check the voltage of a battery, and forgot to turn it off. (This is the most frequent problem I have with DMMs! Yeah, I know, the more expensive ones have an “auto-off” feature, though “feature” is pronounced “flaw”.)

    These days, DMMs can be VERY inexpensive. If you watch the ads (such as in snail-mail), you can often get one for a whopping $0.00 (i.e., “free”) with purchase of anything else at Harbor Freight. True, they’re not really great meters, but I’d say they’re good enough for more than 95% of what I need – e.g., checking batteries (the aforementioned 9V one only read 7.75, which explains why the smoke detector was complaining), verifying that I read the color bands correctly on a resistor, checking continuity, and such. I do have a Fluke for when I either need more accuracy, or need to work on higher voltages. (I’m not comfortable using that $0.00 DMM on a 600V DC solar array circuit that can hit 8 Amps.)

    One other limitation of the not-extreme-high-end DMMs is the inability to accurately measure low resistance values (say below about 5 ohms). You need to use “4-wire” for these (two wires supply the “forcing current”, and two do the voltage measurement). I used such meters back in the mid-70s as an electronics tech in a factory. Within the past couple of months, I had the opportunity to acquire a 5-½ digit DMM from an “estate sale”, but since the last calibration sticker on it is from 95, I’m not sure it’s been powered up in the past 20 years. I haven’t had time yet to get out the Variac and bring it up slowly (reforming the power supply capacitors).

    Oh, yes: another reason for checking resistors is that they sometimes “drift with age” – to the point where one author referred to “carbon composition” resistors as “carbon decomposition” resistors. Which also reminds me: if you’re using a DMM that can do capacitance, and try to measure an electrolytic, polarity IS important (unless the cap is one of the non-polarized versions).

    One more thing: I’ve suggested this to our friends at Adafruit, but maybe SparkFun could get them as a product: wires (maybe about 12" long) with banana plugs on one end, and the “male” pin on the other end to plug into a solderless breadboard. Yeah, you can use a short wire and alligator clips, but I’ve had a lot of trouble with that over the years with shorts and/or the clips falling off or losing contact.

No public wish lists :(