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May 19, 2010
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.
News - Adventures in Science: Ho…
about 1 days ago
One thing I forgot to mention: when using a vernier (no matter how you pronounce it!) if the zeros line up exactly with the fixed marks, you use the fixed mark even with the left zero, and tack a zero on after it.
Although I agree that for really reliable values, you need to use a “standard” (not to mention having everything at the right temperature), but for what most of us do, just using them “as they come out of the store” (usually Harbor Freight), and checking the zero, is good enough for what we do. (If I were trying to do something where I need real accuracy, I wouldn’t use the “Harbor Freight specials”, but those are rare instances, and I’ve always had the luxury of employer-supplied instruments in those cases.)
Good tutorial, Shawn!
Calipers are definitely easier to use than micrometers, and for many purposes, are accurate enough. Each has things that they are better at than the other.
Growing up, I always heard “vernier” pronounced as “vern-EE-uhr” (or “ver-KNEE-er”) rather than “ver-NEAR”. (I still pronounce it the former way.) (Basically, it’s a “long e” followed by a “short e”.)
As for the batteries, mine seem to last on the order of a year, though I don’t use the calipers all that much. My suggestion is to keep a spare. I think I’d find an “external battery” to be excessive in the weight department.
As a side light, I bought my first calipers (I’d been using micrometers) about 20 or so years ago when I was reloading ammunition. One advantage of calipers over micrometers is the large range – from 0 to 6" (or 12") in a single instrument.
News - Adventures in Science: Ho…
about 5 days ago
I beg to differ, for even better reasons…
Although I agree that the analog scopes are often in an “unknown state of repair”, given the cost of a lot of the analog o'scopes, often $20 to $40, even if the ‘scope isn’t working, you’re not out much. If you give it two or three tries, you’ll likely find one that is, at least mostly, working. (Today’s “beginners” should NOT be poking around inside an analog oscilloscope as there are thousands of volts on some of the parts. So the lack of manuals and parts become a moot point.)
Getting state-of-the-art measurement tools IS costly, and, for the professional who has to have the exotic “bells and whistles”, the fancy tools MIGHT be worth the co$t, but for the amateur, especially the beginner, buying a $20,000 test instrument is ABSURD. Yeah, that old analog instrument may not be able to get you the readout and fancy display, but it CAN show you what the waveform looks like.
In about 45 years of using ‘scopes, I know that most of my “hobbyist” usage has no need of “NIST traceable calibrations”. Sure, as a professional, I have had occasion to use only 'scopes that regularly went in for calibration, but when I’m looking at an Arduino that is only 16 MHz, and I’m wondering if the 800 kHz I2C signal is “clean” (or even “present”), that old clunker 20 MHz 'scope that was last calibrated before Shawn was born is fine. (I can bounce the probe off the Vcc line a few times to get an idea where the 5V and ground are on the screen – I really only need to know within a half-volt or so on the readings.)
BTW, for the 100 MHz processors, those frequencies are usually only WITHIN the CPU chip – they’re derived by using Phase-Lock Loops (PLLs) that are referenced to an external crystal that is in the 10 MHz to 20 MHz range. All of the other signals take several clocks to generate. This is especially true for people who are using Arduinos as building blocks – they’ll never need to look at the really high-speed stuff, or, at most, do so to check that the board isn’t “dead”, and even if it happens to be at the rated frequency (and so “reads” about 30% low) that’s “good enough” to know whether the board is “alive” or “dead”.
I say that “entry level” for a ‘scope for the beginner hobbyist is 1/20th what you claim, or 5 MHz, and the last time I saw an old boat-anchor that low at a hamfest (I average about 4 a year) was about 20 years ago, and they were asking $5 for them. They’re plenty for looking at most serial and audio signals, as well as the PWM “psuedo-analog-output” signals. And for a “professional”, 100 MHz may well be a factor of 10 (or more) too LOW, but for the “professional”, someone else is paying for it (and, for high-end stuff, they can be rented or leased).
News - Enginursday: New Product …
about 6 days ago
I’d be afraid that “Homeland Security” would think that the bike was something a lot more malevolent than just a sound system…
News - IoTuesday: Valentine's Bo…
I just realized another approach would be to arrange so that having the box closed maintains continuity, and when the lid is removed, it opens the circuit signalling microcomputer to transmit a message. This would be very easy to do by having a strip of conductive tape on the lid portion of the box that “shorts” two pieces on the lower portion of the box. Of course the downside is that box openings might or might not have a one-to-one correspondence to pieces of chocolate eaten.
Maybe use IR sensors, and hide IR sources in the bathrooms and closets?
News - Adventures in Science: Ho…
Although I think you did an excellent job of covering a “modern” DSO, I really think that you’ve done a disservice to your target audience, namely the hobbyist, especially the “beginner” in electronics. They can look at the prices for DSOs, and USB “pods”, and get scared off. Think, for example, of a teenager who’s mowing lawns (or shoveling snow off sidewalks and driveways), and think about how many lawns (or driveways) need to be done to purchase a brand-new ‘scope (or pod). Now think about the “old clunkers” that can be had at the typical ham-fest at a price that can be covered by mowing a single lawn, sometimes with enough left over to buy a burger for lunch! Sure, a lot of these old clunkers are only 5MHz, and you’ll probably have to buy a probe separately (for maybe 4 or 5 times what the 'scope cost – another lawn or two’s work), but you can still learn a LOT from it. (Yeah, if you want to “document” the image, you’ll have to use your smart phone to take a picture…)
I think you misled folks a bit on bandwidth – the display will still show a sine wave nicely near (or even at) the specified bandwidth, albeit a bit attenuated. The problem comes when you try to examine a differently shaped signal, such as a square wave, where the ‘scope display starts “rounding over” the sharp edges above about 1/5 the bandwidth. (For readers interested in the “why”, look up Fourier Analysis – a topic on which a lot of time is spent by Electrical Engineering students.)
One other point which doesn’t get a lot of coverage: the maximum input voltage. Many of today’s DSO’s and pods will be “smoke emitters” if they are connected by a 1x probe to the wall socket. (I’ll skip the issue of grounding/isolating the scope for now.)
News - Friday Product Post: Fant…
about 2 weeks ago
On the EeonTex Conductive Fabric (as well as on the linked datasheet), it talks about
a tunable surface resistivity of 8 Ohm/sq to 105 Ohm/sq
but there’s no indication as to how the “tuning” (adjustment) is accomplished. Any guidance on this?
about 2 weeks ago
Nate, you may already be using these “tricks”, but I’ll share them here for the benefit of readers working on their own design: First, the use of “through-hole” connectors rather than surface mount connectors will give the best protection against breaking off. Unfortunately, that’s not always possible, and does increase the manufacturing cost even when it is feasible. Second alternative is that some connectors having plastic pins that fit through holes in the board. These are easier to break off than through-hole connectors, but are better than others. The third alternative is connectors with “wings” attached to the “shell”, with the wings soldered to the board. The important thing to do is to make sure that the pads that they’re soldered to have vias to pads on the other side – this gives a measure of mechanical resistance to the pads being “pried off” when stress is applied to the connector. Making sure that the vias have no solder mask on either side can encourage some wicking of solder when they’re soldered, and gives a little additional mechanical strength.
BTW, I’d also include the “via” trick on any surface pad meant to be soldered by hand (especially to wires or connectors). I’ve had problems with this on one of a certain other company’s product. It may have been a “production glitch” with copper adhesion problems, but vias would have likely prevented the problems I had. (FWIW, I have over a half century of experience with soldering, and have only lifted about 3 pads this millennium.)
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