The Printed Solution To A Handful Of Resistors

Resistors are an odd bunch. Why would you have 1.0 Ω resistors, then a 1.1 Ω resistor, but there’s no resistors in between 4.7 Ω and 5.6 Ω? This is a question that has been asked for decades, but the answer is actually quite simple. Resistors are manufactured according to their tolerance, not their value. By putting twenty four steps on a logarithmic scale, you get values that, when you take into account the tolerance of each resistor, covers all possible values. Need a 5.0 Ω resistor? Take a meter to some 4.7 Ω and 5.6 Ω resistors. You’ll find one eventually.

As with all resistor collections, the real problem is storage. With SMD resistors you can stack your reels in stolen milk crates, but for through hole resistors, you’ll need some bins. [FerriteGiant] over on Thingiverse did just that. It’s a 3D printable enclosure that takes all of your E24 series resistors.

The design of this resistor storage solution is a bit like those old wooden cases full of index cards at that building where you can rent books for free. Or, if you like, a handy plastic small parts bin from Horror Fraught. The difference here is that these small cases are designed for the standard length of through-hole resistors, and each of the bins will hold a small 3D printed plaque telling you the value in each bin.

While this is a print that will take a lot of time — [FerriteGiant] spent 100 hours printing everything and used two kilograms of filament — it’s not like through-hole resistors are going away anytime soon. This is a project that you can build and have for the rest of your life, safely securing all your resistors in a fantastic box for all time.

43 thoughts on “The Printed Solution To A Handful Of Resistors

    1. I’ve been wondering this for a while–why are resistor color codes still a thing? We have tiny lettering printed on nearly every other type of component now. Can’t we do away with this weird old-timey code and just print the value on the resistor? Is it a tradition thing?

      Being color blind makes those stripes utterly useless, and like one in ten males is colorblind. I have a little wire cradle hooked up to a dedicated multimeter just for measuring resistors. Toss one onto the cradle in a way that each lead is supported by one y-shaped copper strut and it quickly reads out the resistor, so I don’t have to squint at bands of color and try and tell if something’s green or orange or red or who knows what.

      1. CSB: I worked at DEC in maynard, mass (their HQ) a long time ago; it was a maze of old ‘woolen mills’. buildings that were long and thin and, due to the cold weather, had connecting covered hallways at seemingly random floors. thing is, from building 3, floor 2 you’d take the tunnel hallway and end up in building 4, floor 3. you needed to know what floor you were on.

        you could solve it the boring way or the cool way. the cool way, being you PAINT a single colored line in the center of the wall and continue it for the length of the hallway. when you get out of the elevator or hallway tunnel, you simply look at the color of the stripe and you knew which floor you were on.

        oh yes, they used resistor color codes. when we interviewed people, we asked if they saw anything in ‘3=orange’ and ‘2=red’, etc. some knew this, some did not. but everyone who ended up working in those buildings, did learn the color codes, you can believe that ;)

        1. Hospitals used to use those paint stripes. Sign on the wall with each department’s sign having its own color. Rainbow ran down from it and along the walls, sometimes on the floor. Super easy to find anywhere without needing any instructions.

      2. Totally with you on this. I learned the codes a while back but always had to ask a colleague to read the bands because I’m one of the 10% who is colourblind.
        It staggers me how much of the world misses working for such a large portion of the population.

        Also, I only realised recently how ridiculous lipstick must look. To me red is this dark, subtle colour, but it is apparently really bright, brighter than royal blue!

      3. some precision resistance where not color coded, but text was printed only two time over the diameter, meaning that you need to carefully align it to be able to read them when mounted.
        It is also really hard to read if disposed vertically.

      4. I’m not colorblind, but the difference between brown, red, and orange seems to a bit subjective when you are looking at those tiny little rings. Ditto for green and blue. And is that a gold tolerance ring or a brown first digit? Sometimes I have to get out the meter just to settle the argument.

  1. I probably have close to 30k through hole resistors. Sorted between 1% and 5%, each value in a sharpie marked baggie in order of value. This all sits in cardboard bins made from old yogurt boxes.

    Works really well. I have a little drawer system but the baggies are more convienent, especially for loose resistors. You don’t mix between adjacent bins and i knocked the drawers over once. I still have not sorted them back out. Lol.

  2. Here is my comment regarding resistors/tolerances from a HAD post 2013…

    https://hackaday.com/2013/01/14/papercraft-dial-is-the-slide-ruler-of-current-limiting-resistors/#comment-940205

    “Back in Oct. 1995 on the Usenet group sci.electronics the following was posted in regard to using a sliderule to find resistor values.

    From: Dave Slee
    Newsgroups: sci.electronics
    Subject: Re: Sliderules (do they still exist?)
    Date: Wed, 18 Oct 1995 21:52:16 GMT
    Organization: Soil Machine Dynamics Ltd.

    [deletia]
    I use all sorts of calculators, PCs, computers and micros, but a slide rule is one of the few tools
    that helps you to see beyond the digits and not worry overly about precision, but worry more about magnitude: bigger, smaller, close to and nearly good enough…

    Take your standard slide rule and doctor the scales. Add some new markings:
    the standard resistor values:

    1, 1.5, 2, 2.2, 3.3, 4.7, 5.6, 6.8, etc. (have I missed a few? so what you get the idea)

    Mark them as little dots on the ratio scales.

    Now a pair of scales on a slide rule work on ratios. If you want a potential divider that has a 3:7
    ratio, put the 3 on one scale against the 7 on the other scale. Now find the pair of dots that come
    closest. These are the standard resistor values that are the best approximation to the required
    ratio. The error in dot spacing gives you some idea of how far you are out.”

  3. 100 hours and 2kg of filament? Dang. I use HDX boxes from the homeless despot, they hold up well with lightweight parts like electronics and lock into one another to form a neat stack. Also they have lids, so they’re portable. This seems more like a problem looking for a 3d printed solution.

    1. Yeah. Printing a huge object like this (a type of object which was obviously designed centuries ago to be easy to build out of any form of flat stock) makes my eyes roll hard. This is precisely not what a 3d printer is meant for building. Just get one of those organizer bins for a couple bucks and a marker. Jeez.

  4. QUOTE: “Need a 5.0 Ω resistor? Take a meter to some 4.7 Ω and 5.6 Ω resistors. You’ll find one eventually.:”
    Don’t Think So! I have handled and measured and spec’d resistors for 60 years. Modern resistors are made on machines that have excellent repeatability. Buy 100 of the same garden-variety 5% resistor from a decent source like Digikey. Use a good Digital Multimeter and check it with a known 1% resistor near the values you will test (I have 5 values of .1% resistors in a box on the bench). Now take 10 to 20 resistors from the received batch. Test them. I believe you will find two things: (1) They are much closer to nominal value than 5%, and (2) They will all be within about 2% or less of EACH OTHER. So I think it’s highly unlikely you will ever find a 5.0 Ohm (within say 1%) value in a batch of 4.7 and 5.6 ohm resistors.

    1. True but if you are in an environment where the temperature changes or if you heat it at all by running a current through it the value might change a bit. Don’t get me wrong, it will not change a lot but for 99% of purposes even a spot-on-value 4.7 or 5.6 ohm resistor would be a perfectly fine replacement for a 5 ohm one anyway. For most applications one could stand to be off quite a bit farther even than that.

      So.. if you really DO need a 5 ohm resistor it must mean you are in one of those rare applications where the exact value really does matter. In that case do yourself a favor and order an actual precision resistor. Those come in more “off” values too so you will probably find your 5 ohm resistor that way.

    2. There’s a good anecdote floating around the interwebs somewhere from an engineer who went through a batch of 100 resistors looking for a particular value without finding it. One of the older engineers clued him in as to how it works: in some cases a 5% tolerance batch will be made and the ones that fall inside 2% and 1% are labeled and sold accordingly, leaving none of the 5% resistors within 2% of their marked value. If you need high accuracy, and only have 5% resistors on hand, then the “solution” is to design your circuit around +-4% or so of the E-series values, because you’ll find actual resistors around those ranges.

      1. This was raised in one of my electronics classes: we were asked to draw a curve representing the expected values of 5% resistors, to which most people drew a bell curve, but the official answer was a bell curve missing the central section which are the ones that get sold as 1% tolerance at a much higher price.

  5. Eve if one has a 3D printer, it’s a good idea to consider the wear on the machine, to determine if a project is cost effective when compared to available a commercial product. Now matter how you save a dime, it’s a dime you can spend on another project.

    1. Not to mention it uses two whole dang spools. Not including misprints, which will probably happen at some point with objects this huge and flat. You could buy plenty of organizer boxes with that money.

  6. Not to change the subject, way back when fixing CRT’s was profitable , the RCA CTC169 power supply used a 15uf/63v cap. I asked Ed, the manager of the local parts , “Why a 15uf cap?”. He laughed and said “It was the only one that worked”

  7. I like the idea of 3d printing component cases. Don’t get me wrong, the time/labor vs price balance between printing and buying a single drawer set falls very much on the “just buy it” side.

    The problem I have with buying them is that I’m too cheap to buy as many cases as I will ever want all at once. But I also like uniformity. Things that are meant to stack together are so much easier to organize than a hodge-podge of different makes, models and sizes that were bought separately across a decade or two.

    If I found or made a printable design that I really like I could just pull out the o’l stl every time I want more and all my stuff would still work well together.

    I haven’t found a components case design that I really like yet though. I’m not sure just how 3d printable the ones I like even are. What I like are the divided trays WITH LIDS that then slide into some sort of carrier like drawers. I don’t like the little open-topped drawers that all slide into a cabinet together because they can spill. Also, when they start stacking they become higher than their bases are wide or deep fast meaning they probably will spill.

    I want a way to 3d-print this;

    Only with deeper pockets so that it fits through-hole components without bending them.

  8. I’ve like using three ring binders and trading card page inserts to store and organize my 1/2W and under resistors. For larger wattage resistors though, these printed drawers are a cool approach! Avoids kinked leads and keeps things sorted.

    1. I liked the idea of the binders and card-holder sheets, but those pesky little resistors keep trying to escape, especially since finding a flat space for the binder around my workspace is pretty rare. Anyhow, others have probably thought of this, but I got the idea of using test tubes from this Instructables: https://www.instructables.com/id/Resistor-Organizer-and-Storage/. I was lazier than that person, though. So my solution is more colorful. You can see a picture of mine in the comments over there.

  9. This sort of reminds me of the ohmite ‘little devils’ resistor cabinets. Those were great (I was fortunate enough to find a couple over the years) not sure why no one makes a similar cabinet.

  10. I remember when I was about 7 or 8 years old I wanted to learn about electronics. So I asked our EE neighbor where do start. He gave me a list of numbers and said: learn those. The numbers were 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82.
    I learned them over the next day but it took a while longer before I understood why they were important. And I still don’t know if he genuinely wanted to teach me electronics or if he wanted to discourage me by giving me something abstract and boring to learn. :)

  11. holy shit stains! Has this person heard about lasercutting? So much effort, filament and energy wasted, it’s really disappointing to see 3D-printed things where lasercutting would’ve been cheaper, faster and more convenient. Highly suggest that anyone interested checks out their local hackerspace’s cutter’s capabilities, or pitches the members to throw some cash together and get a K40.

  12. I thought resistors had logarithmic values for the same reason coin values go 1, 2, 5, 10, 20, 50, 100, 200 – you need the smallest number of individual ones to make arbitrary values, and because it covers the widest range of needs given that what you need is probably something within a given range.

  13. I don’t have reels of resistors. But seems to me it would be a great Hack-a-day-baiting project to develop an automated resistor tester that would step through the reel, test the resistor’s value, and print the value on the paper tape. Then you’d just cut out the resistor with the (near-exact) value you are looking for.

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