Any slide rule junkies here?? - Page 1
Forum section: electronics / projects

author: CaptDon
author_rank: Super Contributor
timestamp: February 11, 2021, 03:01:48 pm
content: Greetings all. Any other folks here that started off the electronics career using a slide rule? I am about to give my Sterling DECIMAL TRIG LOG-LOG to a co-worker who is beginning his electronic journey. When I was starting out the cheapest scientific calculator was over $400.00 and that was when $100.00 a week take-home was big money!! I often borrowed my instructors (Jim K3JFL R.I.P.) POST 1460 VERSALOG. I was so impressed with its magnifier and color scales I bought one for myself. I think it was around $50.00 back then and my first 4-function Casio fixed point calculator was around $65.00 I know every smartphone and laptop has a scientific calculator these days, but I think visualizing the numbers and how they interacted on a slide rule gave me a depth of understanding of how numbers describe the functions of electronic building blocks the no electronic calculator could!! My VERSALOG is more of a tinker toy these days, but I am proud to still know how to use it.

author: penfold
author_rank: Frequent Contributor
timestamp: February 11, 2021, 04:15:29 pm
content: Full disclaimer, I was born in a time when home computers were common and my high-school maths teach just looked at the class in despair when he asked us to do a simple addition and everyone reached for their calculator, I remember the phrase "you kids need pocket-brains" was uttered quite often.So when I bought a slide rule at age 20, it was only intended to be a "novelty" item. (it was an Aristo electrical specific one, can't find a model number but had scales for copper resistivity at different temperatures and HP/kW conversion)But I did start to use it on occasion for non-serious calculations, and to me it was pretty eye opening experience. I don't want to suggest it was a massively transcendental experience, but it certainly readjusted my thought process from being very precision focused (and somehow thinking the 9th decimal place was going to affect my circuit) to thinking more about how I can work with lower precision numbers and components to still produce a "precise enough" result. I can certainly visualise how moving the slider left or right will affect my result, but I can't visualise how pressing the wrong number on a calculator will!

author: TimFox
author_rank: Super Contributor
timestamp: February 11, 2021, 04:24:58 pm
content: I still own sliderules, but my elderly eyesight keeps me from enjoying them. An amusing detail about the film Apollo 13 is when the astronauts are loading new parameter values into the navigation computer, and the engineers are checking the numbers with their sliderules back in Houston. I saw two problems: 1. They were using Post bamboo rules (which were very good), but in those days I believe Dietzgen, K&E, and Pickett metal rules were more fashionable in those circles. 2. If I remember correctly, some of the required calculations were addition.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: February 11, 2021, 04:25:35 pm
content: I've got one of thesehttp://www.computinghistory.org.uk/det/22002/British-Thornton-PIC-No-271-Log-Log-Slide-Rule/

author: jpanhalt
author_rank: Super Contributor
timestamp: February 11, 2021, 04:26:19 pm
content: My first was a Pickett cheap one. My second was a better Pickett gift from a man who worked at Pickett. The one I went to college with (circa 1961) was a K&E. Here' s a picture, in case you are a collector. That was taken about 10 years ago after many years of storage. It still worked and just needed cleaning, but I left it that way.

author: CaptDon
author_rank: Super Contributor
timestamp: February 11, 2021, 04:45:00 pm
content: Very nearly identical to my versalog.

author: Stray Electron
author_rank: Super Contributor
timestamp: February 11, 2021, 04:46:08 pm
content: I started out with a slide rule and I still keep a few around. You're lucky that you grew up in the days when calculators were available at any price! My favorite slide rule was one of the circular jobs and even after I bought my first calculator (a TI P.O.S.) I kept that slide rule in the same pouch for use as a backup for when the TI failed (which was often!) I finished HS then went into the military and then worked for about ten more years before going to college so I didn't start college until the mid 1980s and I was still using that slide rule for a backup. People stared at it when I pulled it out to use it during physics tests. I was often the last student in the class to finish the tests but I also got the highest grades in every physics class for two years running. I was a starving student going to school on the GI Bill but I eventually saved up enough money to buy an HP-41 and it was the best investment that I ever made.My daughter recently bought an old house in Arlington, Virginia that was built in 1928 and while going through the attic they found an old slide rule and she sent it to me. It looks it was made in about 1940 and that didn't look like it had been used since about 1943 according to some of the papers that were with it.Walter Sphere in Canada has, or used to have, a nice slide rule collection.https://www.sphere.bc.ca/

author: jonpaul
author_rank: Super Contributor
timestamp: February 11, 2021, 04:48:50 pm
content: As a freshman EE at CCNY we all had the K&E or Picket log log decilog strapped to a belt loop,Thais was 1964..1968.Nowadays have a few straight ones like the old K&E ivory, but especially like special circular rules like for WWII aviation, the AES bomb effects computer and the TEK Circuits computer.Can post photos,Enjoy,Jon

author: jfiresto
author_rank: Frequent Contributor
timestamp: February 11, 2021, 04:52:16 pm
content: I am old enough to have used a slide rule for a few years before I could afford an electronic calculator.I am the latest to use a microscope, introduced in 1970, whose objective is girdled with a simple, circular slide rule: for recalculating exposure times when you zoom in and on. The Chinese copy from the early 1990s left it off.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 11, 2021, 04:57:27 pm
content: I used them in high school and still keep a few around just for the fun of it. Stack those logs!

author: Gyro
author_rank: Super Contributor
timestamp: February 11, 2021, 04:59:14 pm
content: Previous caches...https://www.eevblog.com/forum/chat/slide-rules/https://www.eevblog.com/forum/chat/slide-rules-213218/

author: mawyatt
author_rank: Super Contributor
timestamp: February 11, 2021, 05:04:02 pm
content: Have fond memories back then with the side rule and the CRC math tables book, but couldn't afford a Post so had a cheap plastic slide rule that melted in the car one hot dayRemember in grad school when my friend showed up with the new HP-35 scientific calculator, I couldn't believe they could cram the whole CRC book inside that small calculatorBest,

author: rstofer
author_rank: Super Contributor
timestamp: February 11, 2021, 06:47:01 pm
content: I was a senior in college when the HP 35 became available (around '73). Sadly, I couldn't afford one. I did have a 120V powered 4 function calculator but that's about it.All 4 years of my undergrad was done with a slide rule and i still have a pocket version and a full size version. And, yes, I still remember how to use them.The power of the slide rule wasn't in getting the digits, it was dealing with orders of magnitude and keeping track of the decimal point. Mental math! I still have the ability to get 'close enough' in my head.The slide rule precision was more than adequate when you toss in component tolerances. A couple of digits and an exponent were good enough.

author: Bill158
author_rank: Regular Contributor
timestamp: February 11, 2021, 08:25:54 pm
content: Quote from: jpanhalt on February 11, 2021, 04:26:19 pmWhen I started college in 1958 that was the slide rule I had, and still have. I had a belt hook and wore it slapping my right leg as a badge of being an electronics engineering student. Mine is a little rough but it still works. I don't know where the belt hook is and where the instruction manual is either. My first electronic calculator was a HP 45 which cost $400 in 1974. I had already learned RPN from a HP 35 which I had access to at a job in 1972. But I saw mechanical computers in the Navy where I was a Gun Fire Control Technician. These things dated back to maybe 1950 or even earlier. They were a collection of syncros, servos, motors and variable speed cams which computed where a plane would be when the projectile fired from a 5 inch gun intercepted the flight path of the plane. The input to these computers was a radar which was "locked on" and tracked an incoming enemy plane. It was as big as a refrigerator and was a nightmare to work on if it broke. Sorry just having a trip down memory lane.Bill

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: February 11, 2021, 08:32:06 pm
content: In Wilmington, NC, you can tour the USS North Carolina. It's basically a floating mechanical computer with much as you describe.

author: harerod
author_rank: Frequent Contributor
timestamp: February 11, 2021, 08:47:24 pm
content: The first slide rules I played with, were grandfather's. As a school boy I was fascinated be this first tangible application of logarithms. I only learned to do basic stuff, though.When I started engineering school in 1992 the HP48SX was the bee's knees.Only when I started flying, I got in contact with a circular slide rule, the famous E6-B.Even though I am a pedestrian now, I find some consolation in the fact that Mr Spock will be using the same flight computer in a couple of hundred years' time...

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 11, 2021, 09:12:44 pm
content: I started on slide rules, and continued to use specialty rules (General Electric's Infrared Slide Rule for example) until the HP-65 came out and allowed extending the pocket calculator into niche areas. The CRC math tables and particularly the Government Printing Office numerical methods book was still a mainstay when I retired. They were the information sources and check data for programs.Another value of the slide rule was enforcing the realization that for most real world problems more than 3 digit precision is rarely needed or warranted. Outside of the Metrology world few measurements are known to that or higher precision, so doing a calculation to six or seven digits is merely a demonstration of ignorance. And a skilled operator with young eyes can coax three or more digits out of a slide rule.I still have several rules and haven't used them for anything other than fun for thirty or more years.

author: TimNJ
author_rank: Super Contributor
timestamp: February 11, 2021, 09:34:31 pm
content: Quote from: rstofer on February 11, 2021, 06:47:01 pmInteresting. Born in 1994...so I'm a couple decades late to the party, but did buy myself a K&E deci-trig rule off eBay a while ago. I played with a it a little bit. At the time, I had a few "aha" moments, but I've since forgotten what I found so interesting about it. I'll have to try it again, with your ideas in mind!

author: jpanhalt
author_rank: Super Contributor
timestamp: February 11, 2021, 10:03:36 pm
content: Hey Tim,Clean up your K&E and learn to use it. The big lesson is how to set up the problem. Lubricate it with unscented talc or boron hydride (we didn't have the latter in school).Now, solve this: The Earth has a circumference of 25,000 miles. If you stretch a rope around it (assume no stretch), and then add 1 foot to it, how much will the rope be above the surface? That is easily solved to 3 significant figures with your slide rule, and is an example of a typical problem my generation faced in school.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 11, 2021, 10:04:34 pm
content: Hey Tim,Clean up your K&E and learn to use it. The big lesson is how to set up the problem. Lubricate it with unscented talc or boron hydride (we didn't have the latter in school).Now, solve this: The Earth has a circumference of 25,000 miles. If you stretch a rope around it (assume no stretch), and then add 1 foot to it, how much will the rope be above the surface? That is easily solved to 3 significant figures with your slide rule and is an example of a typical problem my generation faced in school.

author: TimNJ
author_rank: Super Contributor
timestamp: February 11, 2021, 10:21:09 pm
content: Quote from: jpanhalt on February 11, 2021, 10:04:34 pmOh boy. As B/B+ math student now living in Excel engineering world, this will be a fun one for me.Source: T3sl4co1lBut really, thanks for the tip about the dry lube. It could definitely use it.

author: TimFox
author_rank: Super Contributor
timestamp: February 11, 2021, 10:52:37 pm
content: Contrary to popular opinion, there is algebra in the "real world", and it is all story problems.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 11, 2021, 11:30:34 pm
content: Quote from: TimNJ on February 11, 2021, 10:21:09 pmIt's cheap. It's a great, non-electrically conductive filler for epoxy or whatever.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: February 11, 2021, 11:55:55 pm
content: Quote from: jpanhalt on February 11, 2021, 10:04:34 pmThe circumference is irrelevant. All you need to know is that your are increasing the circumference of a circle by 1ft and therefore its radius by 1/2pi ft. Which is about 0.16 in my head (0.159 to 3 sf).Figuring sh!t out in your head and/or doing order-of-magnitude calculations also seem lost skills.

author: mawyatt
author_rank: Super Contributor
timestamp: February 12, 2021, 12:39:04 am
content: Quote from: rstofer on February 11, 2021, 06:47:01 pmExactly, you learned to think about the result rather than just key in the numbers.Same goes for circuit design. When I was an adjunct prof teaching grad school, I would get upset with students that would start right off to Cadence instead of sketching the circuit and doing some hand analysis before relying on the computer. I would ask how do you know that the computer didn't lie or mislead you??Best,

author: ferdieCX
author_rank: Regular Contributor
timestamp: February 12, 2021, 01:49:20 am
content: I got an Aristo 0969 when started the technical high school in 1975. I used it also in the college and several years after that for private things.It was easy to get 3 digits, enough for the tolerance of normal components.I still have it, it works perfectly and I still know how to use it.

author: TimNJ
author_rank: Super Contributor
timestamp: February 12, 2021, 02:32:29 am
content: Regarding lubricants, as I can’t find any unscented talcum powder around my place, and talcum baby powder has some additional ingredients (fragrances), looks like I’m eBaying 5.5oz of talcum powder shipped in a plastic baggie!! What could go wrong!?

author: gnuarm
author_rank: Super Contributor
timestamp: February 12, 2021, 02:49:12 am
content: Quote from: TimFox on February 11, 2021, 04:24:58 pmWow, this thread is already 2 pages long. I recall Picket being all the rage. I had three at different times. Being a kid I couldn't hang on to one terribly long. By the time I got to college 4 bangers were out for $100. I waited a year and the TI with much more functionality was $150 so I got one. The HPs were the gold standard but much more money.We weren't allowed to use calculators on exams as that was an unfair economic advantage. Didn't matter much really. I could do any calculation to 3 decimal places using a slide rule as fast as a calculator could be punched, often faster. Now I do math in my head. Turns out if you practice finding short cuts, lots and lots of arithmetic has short cuts you can exploit if you try. It helps if you picture the math as a physical problem, like blocks in rows or eggs in a carton. In fact, that's how they teach arithmetic in elementary school these days, with images and physical things you can manipulate. Not so much of the rote learning.

author: harerod
author_rank: Frequent Contributor
timestamp: February 12, 2021, 09:00:08 am
content: At engineering school they trained us to do calculations in our heads, not even using slide rules. So that cool HP48SX lay right on the desk, but we simply didn't have the time to punch keys. I always considered myself fairly slow, compared to what my elders could do. Nowadays, when I see gaping mouths when I do rough estimates (Überschlagsrechnungen) on the fly, in my head, hitting the target within a few percent, I see what really has been lost over the last few decades.One skill the slide rule gave you, was sense and sensibility for orders of magnitude. I am still, barely, on the good side of fifty, but it is sad to see younger engineers trusting the results of a computer / calculator implicitly, without even thinking of doing a sanity check.

author: mawyatt
author_rank: Super Contributor
timestamp: February 12, 2021, 10:48:55 pm
content: Quote from: harerod on February 12, 2021, 09:00:08 amExactly!! If the computer produces a result, younger folks tend to believe it!! Recall over 20 years ago giving a design review at Bell Labs on a new (maybe the 1st) MW Single Chip Silicon receiver based upon a synchronous homo-dyne architecture (Zero IF), much later patented (560311). A Bell Labs Fellow (Dr Paul Davis) in attendance made a commit about increasing the emitter size of a unique current-mode RF amplifier transistor would improve the gain by 0.1~0.2dB and ever so slightly improve the receiver Noise Figure. After the review, when we returned to the simulator, he was right and realized he could do SPICE like simulations in his head!! That's when we set out to be able to do the same. Never achieved Paul's amazing ability but did improve our ability to look and analyze a schematic circuit and get some idea of the bias and waveforms expected. This has proved very valuable over the years in IC research, design and reviews. I'm forever indebted to Paul and his unique ability to "feel the silicon" as we used to say.Best,

author: wizard69
author_rank: Super Contributor
timestamp: February 13, 2021, 02:44:19 am
content: Sadly my experience with slide rules amounted to running up to the kitchen table, with my nose at the edge, watching my father use his. At some point he got a Radio Shack calculator with a square root function, apparently important to him and that slide rule never came out again. What was cool, back then anyways, was the tiny LED display. The numbers where very small which made reading the display a chore.It was years later in high school when I got a calculator of my own, I can't even remember what it was. Probably an HP because my mind has been RPN ever since. I believe in my senior year I upgrade to an HP 41. So the lasting impression of those early years was RPN as I now have RPN based calculators on my cell phone and all computers. I never did learn to use dads slide rule even though he did show me something once or twice. I suspect he didn't see much of a future in the things and I wasn't even in grade school so not much effort put into the slide rule.

author: gnuarm
author_rank: Super Contributor
timestamp: February 13, 2021, 04:23:43 am
content: Quote from: wizard69 on February 13, 2021, 02:44:19 amA slide rule is very easy to use if you understand logarithms. The scale is graduated in the log of the number, so aligning the 1 on the slide with a number on the fixed rule adds that log to the log of the second number on the slide. Read the product on the fixed rule using the cursor which let you accurately subdivide the divisions marked on the rule.Division is done by subtraction of the log. One scale was offset by pi to make pi multiplications easy. Squares and square roots require a separate scale that ranges 1 to 100 rather than just 1 to 10. The square root has a domain of 1 to 100 for a range of 1 to 10. There was a linear scale to get logs and other scales to get trig functions. Each scale had a name, one letter or I think some had digits too. I could find out by going in the other room, but I'm warm here and it's cold out there. lolI don't have my slide rules handy anymore, but a few years ago a 94 year old engineer friend gave me his old slide rules he used to design pumps to run refineries and cool nuclear reactors. He never worked on a pump he couldn't fit his head into the discharge pipe. I was actually touched that he gave his slide rules to me. He knew that I would understand. I have the better one of his slide rules on an old drafting table in my living room.Oh, here's one online...https://www.sliderules.org/

author: Keith956
author_rank: Regular Contributor
timestamp: February 13, 2021, 07:44:48 am
content: Got my first, and only, slide rule back in 1970 when I was 14. In those days the only alternative was log tables (remember them?). A friend had a funky one (Otis?) that was tubular, so the scale was effectively several feet long. They are collector's items now.A few years later in 1976 I got a Casio FX-201P calculator and the slide rule was consigned to the bin. I still have that calculator, and still use it nearly every day as it's got a nice bright electroluminescent display, decent sized buttons and the batteries last ages.