Misc Hacks

4165 Articles

Incandescent 7-Segment Displays Are Awesome

April 20, 2021 by 17 Comments

When we think of 7-segment displays as the ubiquitous LED devices that sprung into popularity in the 1970s. However, numbers have existed for a lot longer than that, and people have wanted to know what the numbers are for quite some time, too. Thus, a variety of technologies were used prior to the LED – such as these magnificent incandescent 7-segment displays shown off by [Fran Blanche].

The displays are basic in concept, but we imagine a little frustrating in execution. Electronics was tougher back in the days when valves needed huge voltages and even a basic numerical display drew a load of current. Built to industrial-grade specifications, they’re complete with a big heatsinking enclosure and rugged gold-plated connectors. [Fran] surmises that due to the likely military applications of such hardware, the filaments in the bulbs were likely built in such a way as to essentially last indefinitely. The glow of the individual segments has a unique look versus their LED siblings; free of hotspots and the usual tapered shape on each segment. Instead, the numerals are pleasingly slab-sided for a familiar-but-not-quite aesthetic.

[Fran] demonstrates the display running with a CD4511B BCD-to-7-segment decoder, hooked up with a bunch of 3904 power transistors to get the chip working with filament bulbs instead of LEDs. It’s a little fussy, but the displays run great with the hardware sorted.

We’d love to see these used on a very heavy ridiculous watch; nixies aren’t the only game in town after all. If you do happen to make one, be sure to let us know. Video after the break.

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Large Format Lego Camera Is A Bit Near-Sighted

April 19, 2021 by 7 Comments

Photography doesn’t have to be expensive, something that’s especially true in the realm of film photography, where the imperfections of the medium can be half the appeal. There are many DIY plans and kits available for analog cameras, but [bhiga143] had couple spare components and a pile of small, colorful bricks lying around, so he decided to build a functional 4×5″ film camera out of Lego.

Details are light for this build, but with a little knowledge about camera structure we can guess at what’s going on inside. Simplicity makes for robust design, and what we have here is in effect a box with a lens on one side and photographic film on the other. The center section of the front, which actually supports the lens, is capable of sliding in and out to adjust focus. On the far side (not pictured) is a slot just wide enough to insert a standard film holder.

The camera really is a hack. [bhiga143] stayed true to the “Lego” part of Lego camera, so there is no glue, no black paper lining, and no frills. The tripod is whatever stack of books lay underneath it. The lens is, quote, “barely functional”. There are light leaks galore, and it can’t focus beyond about 3 feet (1 meter). But every one of those points just makes us love it more. Every nugget of imperfection is a few words added to the story each picture tells. And we honestly can’t wait to see more pictures.

Other Lego cameras we’ve seen have been smaller and less colorful, but using a simple pinhole lens can reduce the overall cost. Of course, you’re not limited to Lego if you want to build your own pinhole camera. Although, the ubiquitous plastic bricks can also be useful in later stages of the film photography process.

Toggle Switch Puzzle Boggles The Mind, Opens The Box

April 18, 2021 by 13 Comments

We all have too much stock of one component or another. Maybe you have more audio pots than you know what to do with, or maybe it’s zener diodes. For [technologyguy], that thing is a pile of toggle switches.  Fortunately he’s always wanted to build a locking box with a binary code that’s laid out in switches — as in, find the right code, and a solenoid unlatches the box. This lovely parts bin special only responds to two combinations out of a possible 4,000+, so anyone who tries to open it should probably block out the afternoon.

Inside you’ll find two 9 V batteries, a home-brew metal latch, a solenoid, and the undersides of four DPDT and eight SPDT toggle switches. If you just picked this thing up and had no idea what was going on, you’d be so screwed as to what to do first. The box needs power, so you’d have to figure out which switch is which. But it’s so much harder than that, because the bottom left switch selects between the two paths that result in an unlocked book-box.

The next two toggles in from the left are on/off selectors for code A and code B, so not only do you have to have the right path chosen, you have to power it, too. The only progress indicators are the LEDs — there’s one for main power, and the other lets you know that the box is unlatched. What a fun conversation piece for the coffee table Zoom-viewable area!

Want to do something far less useful with your throng of toggles? How about a complicated useless machine?

Kitchen Bump Bar Plays Doom Between Orders

April 17, 2021 by 6 Comments

For as much as we love reverse engineering projects, we have to admit that we almost passed up on this “kitchen bump bar” hack. Having never had the privilege of working in the food-service industry — well, there was that time working at Chuck E. Cheese’s, but that only lasted for one shift — we were unaware of what a bump bar is, and the whys and hows of hacking one to the point where it can play Doom.

We’re glad we stuck with it, though, because [Kiwa]’s hack is pretty cool, and we got to learn a little about the technology of the modern commercial kitchen. Most fast food and family casual restaurants have what’s known as a “kitchen display system”, which relays orders from the wait staff to the kitchen. You’ve probably seen parts of the KDS, like the touch screens used by the wait staff to enter orders, or the screens dangling in the kitchen that display the pending orders. A bump bar is a small terminal used by the kitchen crew to review orders and move them around in the queue, or “bump” them, as needs dictate.

The bump bar [Kiwa] dug into appears to be a model from the early 2000s and very sturdily built, as anything used in a kitchen would need to be. Hooked up to a monitor and a keyboard, [Kiwa] discovered that it booted right into an OS with all the familiar trappings of DOS. After a detour for a teardown and dumping the flash contents, [Kiwa] was able to boot it up and run Doom, albeit somewhat slowly. It also looks like he’s got a couple of different Windows versions running, and even played some Solitaire.

It’s always fun to see what will run Doom — an NES, an oscilloscope, a thermostat, or even a bag of potatoes.

Thanks to [Fritnando] for the tip.

The Imperfect Bipolar Transistor

April 16, 2021 by 15 Comments

We like to pretend that our circuit elements are perfect because, honestly, it makes life easier and it often doesn’t matter much in practice. For a normal design, the fact that a foot of wire has a tiny bit of resistance or that our capacitor value might be off by 10% doesn’t make much difference. One place that we really bury our heads in the sand, though, is when we use bipolar transistors as switches. A perfect switch would have 0 volts across it when it is actuated. A real switch won’t quite get there, but it will be doggone close. But a bipolar transistor in saturation won’t be really all the way on. [The Offset Volt] looks at how a bipolar transistor switches and why the voltage across it at saturation is a few tenths of a volt. You can see the video below.

To understand it, you’ll need a little bit of math and some understanding of the construction of transistors. The idea of using a transistor as a switch is that the transistor is saturated — that is, increasing base current doesn’t make much change in the collector current. While it isn’t perfect, it is good enough to switch a relay or do other common switching tasks.

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Detergent DRM Defeated On Diminutive Dishwasher

April 16, 2021 by 71 Comments

Has it really come to this? Are we really at the point that dishwashers have proprietary detergent cartridges that you’re locked into buying at inflated prices?

Apparently so, at least for some species of the common kitchen appliance. The particular unit in question goes by the friendly name of Bob, and is a compact, countertop unit that’s aimed at the very small kitchen market. [dekuNukem] picked one of these units up recently, and was appalled to learn that new detergent cartridges would cost an arm and a leg. So naturally, he hacked the detergent cartridges. A small PCB with an edge connector and a 256-byte EEPROM sprouts from each Bob cartridge; a little reverse engineering revealed the right bits to twiddle to reset the cartridge to its full 30-wash count, leading to a dongle to attach to the cartridge when it’s time for a reset and a refill.

With the electronics figured out, [dekuNukem] worked on the detergent refill. This seems like it was the more difficult part, aided though it was by some fairly detailed specs on the cartridge contents. A little math revealed the right concentrations to shoot for, and the ingredients in the OEM cartridges were easily — and cheaply — sourced from commercial dishwashing detergents. The cartridges can be refilled with a properly diluted solution using a syringe; the result is that each wash costs 1/75-th of what it would if he stuck with OEM cartridges.

For as much as we despise the “give away the printer, charge for the ink” model, Bob’s scheme somehow seems even worse. We’ve seen this technique used to lock people into everything from refrigerator water filters to cat litter, so we really like the way [dekuNukem] figured everything out here, and that he saw fit to share his solution.

You Need An Automated Overhead Camera Assistant

April 14, 2021 by 13 Comments

It’s 2021. Everyone and their mother is filming themselves doing stuff, and a lot of it is super cool content. But since most of us have to also work the video capture devices ourselves, it can be difficult to make compelling footage with a single, stationary overhead view, especially when there are a lot of steps involved. A slider rig is a good start, but the ability to move the camera in three dimensions programmatically is really where it’s at.

[KronBjorn]’s excellent automated overhead camera assistant runs on an Arduino Mega and is operated by typing commands in the serial monitor. It can pan ±20° from straight down and moves in three axes on NEMA-17 stepper motors. It moves really smoothly, which you can see in the videos after the break. The plastic-minimal design is interesting and reminds us a bit of an ophthalmoscope phoropter — that’s that main rig at the eye doctor. There’s only one thing that would make this better, and that’s a dedicated macro pad.

If you want to build your own, you’re in luck — there’s quite a lot of detail to this project, including a complete BOM, all the STLs, code, and even assembly videos of the 3D-printed parts and the electronics. Slide past the break to check out a couple of brief demo videos.

Not enough room for a setup like this one? Try the pantograph version.

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