resistor

59 Articles

Otis Boykin’s Precision Passives Propelled The Pacemaker

September 16, 2020 by 11 Comments

The simplest ideas can be the ones that change the world. For Otis Boykin, it was a new way to make wirewound precision resistors. Just like that, he altered the course of electronics with his ideas about what a resistor could be. Now his inventions are in everything from household appliances and electronics to missile guidance computers.

While we like to geek out about developments in resistor tech, Otis’ most widely notable contribution to electronics is the control unit he designed for pacemakers, which regulate a person’s heartbeat. Pacemakers are a real-time clock for humans, and he made them more precise than ever.

Street Smarts and Book Smarts

Otis Frank Boykin was born August 29th, 1920 in Dallas, Texas to Sarah and Walter Boykin. Otis’ father was a carpenter who later became a preacher. His mother Sarah was a maid, and she died of heart failure when Otis was only a year old.

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Hacking A ThinkPad USB-C Adapter

June 28, 2020 by 29 Comments

USB-C has brought the world much more powerful charging options in a slimline connector. With laptop chargers and portable battery packs using the standard, many with older hardware are converting their devices over to work with USB-C. [victorc] was trying to do just that, purchasing an adapter cable to charge a ThinkPad. Things didn’t quite work out of the box, so some hacking was required.

The problem was the power rating of the adapter cable, versus the battery pack [victorc] was trying to use. In order to allow the fastest charging rates, the adapter cable features a resistor value which tells the attached Lenovo laptop it can draw up to 90 W. The battery pack in question could only deliver 45 W, so it would quickly shut down when the laptop tried to draw above this limit.

To rectify this, [victorc] looked up the standard, finding the correct resistor value to set the limit lower. Then, hacking open the cable, the original resistor on the Lenovo connector was removed, and replaced with the correct value. With this done, the cable works perfectly, and [victorc] is able to charge their laptop on the go.

For all the benefits USB-C has brought, there’s been plenty of consternation, too. Whether this clears up, only time will tell!

Matrix Of Resistors Forms The Hot Hands Behind This Thermochromic Analog Clock

May 24, 2020 by 22 Comments

If you’re going to ditch work, you might as well go big. A 1,024-pixel thermochromic analog clock is probably on the high side of what most people would try, but apparently [Daniel Valuch] really didn’t want to go to work that day.

The idea here is simple: heat up a resistor by putting some current through it, lay a bit of thermochromic film over it, and you’ve got one pixel. The next part was not so simple: expanding that single pixel to a 32 by 32 matrix.

To make each pixel square-ish, [Daniel] chose to pair up the 220-ohm SMD resistors for a whopping 2,048 components. Adding to the complexity was the choice to drive them with a 1,024-bit shift register made from discrete 74LVC1G175 flip flops. With the Arduino Nano and all the other support components, that’s over 3,000 devices with the potential to draw 50 amps, were someone to be foolish or unlucky enough to turn on every pixel at once. Luckily, [Daniel] chose to emulate an analog clock here; that led to additional problems, like dealing with cool-down lag in the thermochromic film when animating the hands, which had to be dealt with in software.

We’ve seen other thermochromic displays before, including recently with this temperature and humidity display. This one may not be the highest resolution display out there, but it’s big and bold and slightly dangerous, and that makes it a win in our book.

Resistors Sorter Measures Values

May 23, 2020 by 22 Comments

We’ve all been there. A big bag of resistors all mixed up. Maybe you bought them cheap. Maybe your neatly organized drawers spilled. Of course, you can excruciatingly read the color codes one by one. Or use a meter. But either way, it is a tedious job. [Ishann’s] solution was to build an automatic sorter that directly measures the value using a voltage divider, rather than rely on machine vision as is often the case in these projects. That means it could be modified to do matching for precise circuits (e.g., sort out resistors all marked 1K that are more than a half-percent away from one nominal value).

There is a funnel that admits one resistor at a time into a test area where it is measured. A plate at the bottom rotates depending on the measured value. In the current implementation, the resistor either falls to the left or the right. It wouldn’t be hard to make a rotating tray with compartments for different values of resistance. It looks like you have to feed the machine one resistor at a time, and automating that sounds like a trick considering how jumbled loose axial components can be. Still, its a fun project that you probably have all the parts to make.

An Arduino powers the thing. An LCD screen and display control the action. If you want some practice handling material robotically, this is a great use of servos and gravity and it does serve a practical purpose.

We have seen many variations on this, including ones that read the color code. If you ever wanted to know where the color code for resistors came from, we took a trip to the past to find out earlier this year.

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The $50 Ham: Dummy Loads, Part 2

May 17, 2019 by 21 Comments

In the last installment of “The $50 Ham” I built a common tool used by amateur radio operators who are doing any kind of tuning or testing of transmitters: a dummy load. That build resulted in “L’il Dummy”, a small dummy load intended for testing typical VHF-UHF handy talkie (HT) transceivers, screwing directly into the antenna jack on the radio.

As mentioned in the comments by some readers, L’il Dummy has little real utility. There’s actually not much call for a dummy load that screws right into an HT, and it was pointed out that a proper dummy load is commercially available on the cheap. I think the latter observation is missing the point of homebrewing specifically and the Hackaday ethos in general, but I will concede the former point. That’s why at the same time I was building L’il Dummy, I was building the bigger, somewhat more capable version described here: Big Dummy.

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Wire Wound Resistors On Your Own

July 21, 2018 by 17 Comments

In all kinds of engineering, we build on abstractions in a kind of inverted pyramid. Lots of people can, for example, design a system using ready-made building blocks on printed circuit boards. Fewer people can do the same design using ICs. Fewer still can design with components. But who designs the components? Even fewer people. Then there are the people designing the constituent elements of those components. [Learnelectronics] wanted to break one of those abstraction layers so he shows how to make your own wire-wound resistors.

Wire-wound resistors are often used when you need resistance with a higher power dissipation than a common film or composition resistor. Using nichrome wire makes this more practical since a meter of it has nearly 20 ohms of resistance. A regular wire has much less resistance.  The video shows a drill winding a coil of wire neatly, but this also highlights one of the problems with wire wound resistors.

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GPS synchronized Nixie tube clock from kit

3D Printed Tool Tips To Straighten DIP Chips And Unstraighten Resistors

May 10, 2018 by 21 Comments

Watching someone assemble a kit is a great way to see some tools you may have not encountered before and maybe learn some new tricks. During [Marco Reps’] recent build of a GPS synchronized Nixie clock kit we spied a couple of handy tools that you can 3D print for your own bench.

Fresh from the factory Dual Inline Package (DIP) chips come with their legs splayed every so slightly apart — enough to not fit into the carefully designed footprints on a circuit board. You may be used to imprecisely bending them by hand on the surface of the bench. [Marco] is more refined and shows off a neat little spring loaded tool that just takes a couple of squeezes to neatly bend both sides of the DIP, leaving every leg the perfect angle. Shown here is a 3D printed version called the IC Pin Straightener that you can throw together with springs and common fasteners.

Another tool which caught our eye is the one he uses for bending the metal film resistor leads: the “Biegelehre” or lead bending tool. You can see that [Marco’s] tool has an angled trench to account for different resistor body widths, with stepped edges for standard PCB footprint spacing. We bet you frequently use the same resistor bodies so 3D printing is made easier by using a single tool for each width. If you really must copy what [Marco] is using, we did find this other model that more closely resembles his.

As for new tricks, there are a lot of small details worth appreciating in the kit assembly. [Marco] cleans up the boards using snips to cut away the support material and runs them over sandpaper on a flat surface. Not all Nixie tubes are perfectly uniform so there’s some manual adjustment there. And in general his soldering practices are among the best we’ve seen. As usual, there’s plenty of [Marco’s] unique brand of humor to enjoy along the way.

We have a warm spot in our heart for simple tools you can whip up on the ‘ole 3D printer. Check out the PCB vise, a set of ball and socket helping hands, and a collection of toolbag essentials.

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