Automate Your Pin Header Chopping Chores Away

In most cases, cutting pin headers is a pretty simple job to tackle with a pair of cutters or even your bare fingers. But if you’re doing a lot of it, like for kitting up lots of projects for customers, then you might want to look at something like this automatic pin header cutter.

Even if you don’t need to follow [Mr. Innovative]’s lead on this, it’s worth taking a look at the video below, which has a couple of cool ideas that are probably applicable to other automation projects, especially those where lots of small parts are handled. Processing begins with a hopper that holds a stack of header strips over what we’d call a “reverse guillotine,” consisting of a spring-loaded plunger riding on a cam. A header strip is pushed out of the hopper to expose the specified number of terminals, the cam rotates and raises the plunger, and the correct length header is snapped off.

For our money, the neatest part of this build is the feed mechanism for the hopper. Rather than anything complicated like a rack-and-pinion, [Mr. Innovative] opted for a pusher made from a stiff yet flexible strip of plastic, which is forced along the bottom of the hopper by a pair of stepper-driven drive rollers. The plastic pusher is stored rolled up in a spiral fixture so it doesn’t take up much room.

Overall, it’s a simple and largely effective design. [Mr. Innovative] does express a little dissatisfaction with some aspects of the build, though; it looks like the stack of header strips needs a little weight on top of it to keep them feeding properly, and we notice a couple of iterations of the cutting mechanism in the video. The cut headers do seem to either fly off into the stratosphere or stay attached to each other, which could lead to jamming problems.

But still, it’s a solid design and reminds us of some other projects by [Mr. Innovative], like this SMD tape slicer or a CNC gear cutter.

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Flip-Segment Digital Clock Is A Miniature Mechanical Marvel

Clocks are such mundane objects that it’s sometimes hard for them to grab your attention. They’re there when you need them, but they don’t exactly invite you to watch them work. Unless, of course, you build something like this mechanical flip-segment clock with a captivating exposed mechanism

“Eptaora” is the name of this clock, according to its inventor [ekaggrat singh kalsi]. The goal here was to make a mechanical flip-segment display as small as possible, which meant starting with the smallest possible printable screw hole and scaling the design up from there. Each segment is controlled by a multi-lobed cam which bears on a spring-loaded cam follower. When the cam rotates against the follower, a segment is flipped up from the horizontal rest position to the vertical display position. A carryover mechanism connects two adjacent displays so that each pair of digits can be powered by a single stepper, and the finished clock is quite small — a little bit larger than the palm of a hand. The operation seems quite smooth, too, which is always a bonus with clocks such as these. Check out the mesmerizing mechanism in the video below.

We’d have sworn we covered a similar clock before — indeed [ekaggrat] says the inspiration for this clock came from one with a similar mechanism — but we couldn’t find it in the back catalog. Oh sure, there are flip-up digital clocks and all manner of mechanical seven-segment displays, but this one seems to be quite unique, and very pleasing.

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Mechanical 7-segment display

A One-Servo Mechanical Seven-Segment Display

The seven-segment display may be a bit prosaic after all these years, but that doesn’t mean there aren’t ways to spice it up. Coming up with a mechanical version of the typical photon-based display is a popular project, of which we’ve seen plenty of examples over the years. But this seven-segment display is quite a mechanical treat, and a unique way to flip through the digits.

With most mechanical displays, we’re used to seeing the state of each segment changed with some kind of actuator, like a solenoid or servo. [Shinsaku Hiura] decided on a sleeker design using a 3D-printed barrel carrying one cam for each segment. Each hinged segment is attached to an arm that acts as a follower, riding on its cam and flipping on or off in a set pattern. Which digit is displayed depends on the position of the barrel, which is controlled with a single servo and a pair of gears. It trades mechanical complexity for electrical simplicity and overall elegance, and as you can see from the video below, it’s pretty snappy.

We think the best part of this build is figuring out the shape of the cams. We wonder how they compare to the cam profiles in [Greg Zumwalt]’s mechanical display; it uses two separate discs with grooves, but the principle is pretty much the same.

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OPARP Telepresence Robot

[Erik Knutsson] is stuck inside with a bunch of robot parts, and we know what lies down that path. His Open Personal Assistant Robotic Platform aims to help out around the house with things like filling pet food bowls, but for now, he is taking one step at a time and working out the bugs before adding new features. Wise.

The build started with a narrow base, an underpowered RasPi, and a quiet speaker, but those were upgraded in turn. Right now, it is a personal assistant on wheels. Alexa was the first contender, but Mycroft is in the spotlight because it has more versatility. At first, the mobility was a humble web server with a D-pad, but now it leverages a distance sensor and vision, and can even follow you with a voice command.

The screen up top gives it a personable look, but it is slated to become a display for everything you’d want to see on your robot assistant, like weather, recipes, or a video chat that can walk around with you. [Erik] would like to make something that assists the elderly who might need help with chores and help connect people who are stuck inside like him.

Expressive robots have long since captured our attention and we’re nuts for privacy-centric personal assistants.

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Mechanical Seven-Segment Display Mixes Art With Hacking

We’re not sure what to call this one. Is it a circuit sculpture? Sort of, but it moves, so perhaps it’s a kinetic circuit sculpture. Creator [Tomohiro Tsuchita] calls it “something beautiful but totally useless,” which we find a tad harsh. But whatever you call it, we think this mechanical seven-segment display is really, really cool.

Before anyone gets to thinking that this is something like the other mechanical seven-segment displays we’ve seen lately, think again. This one is not addressable; it simply goes through the ten digits in order. So you won’t be building a clock from it, although we suppose the mechanism could be modified to allow that. Then again, looking at that drive train of laser-cut acrylic cams, maybe not. Each segment has its own cam with lobes or valleys for each segment. A cam follower lowers and raises the segments as the cams rotate on a common shaft. A full-rotation servo powers the display under the control of a Micro:bit; the microcontroller is overkill for now but will be used in version two, which will allow the speed to change in response to sensors.

Watching this display change at its stately pace is strangely soothing. We love the look of this, but then again, we’re partial to objets d’art-circuit. After all, we ran a circuit sculpture contest earlier in the year, and just wrapped up a Hack Chat dedicated to the subject.

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Geared Cable Winder Keeps Vive Sync Cable Neatly Wound

Long cables are only neat once – before they’re first unwrapped. Once that little cable tie is taken off, a cable is more likely to end up rats-nested than neatly coiled.

Preventing that is the idea behind this 3D-printed cable reel. The cable that [Kevin Balke] wants to make easier to deal with is a 50 foot (15 meters) long Vive lighthouse sync cable. That seems a bit much to us, but it makes sense to separate the lighthouses as much as possible and mount them up high enough for the VR system to work properly.

[Kevin] put a good deal of effort into making this cable reel, which looks a little like an oversize baitcasting-style fishing reel. The cable spool turns on a crank that also runs a 5:1 reduction geartrain powering a shaft with a deep, shallow-pitch crossback thread. An idler runs in the thread and works back and forth across the spool, laying up the incoming cable neatly. [Kevin] reports that the reciprocating mechanism was the hardest bit to print, as surface finish affected the mechanism’s operation as much as the geometry of the mating parts. The video below shows it working smoothly; we wonder how much this could be scaled up for tidying up larger cables and hoses.

This is another great entry in our 3D Printed Gears, Pulleys, and Cams Contest. The contest runs through February 19th, so there’s still plenty of time to get your entries in. Check out [Kevin]’s entry along with all the others, and see what you can come up with.

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Biasing That Transistor: The Emitter Follower

We were musing upon the relative paucity of education with respect to the fundamentals of electronic circuitry with discrete semiconductors, so we thought we’d do something about it. So far we’ve taken a look at the basics of transistor biasing through the common emitter amplifier, then introduced a less common configuration, the common base amplifier. There is a third transistor amplifier configuration, as you might expect for a device that has three terminals: the so-called Common Collector amplifier. You might also know this configuration as the Emitter Follower. It’s called a “follower” because it tracks the input voltage, offering increased current capability and significantly lower output impedance.

The emitter follower circuit
The emitter follower circuit

Just as the common emitter amplifier and common base amplifier each tied those respective transistor terminals to a fixed potential and used the other two terminals as amplifier input and output, so does the common collector circuit. The base forms the input and its bias circuit is identical to that of the common emitter amplifier, but the rest of the circuit differs in that the collector is tied to the positive rail, the emitter forms the output, and there is a load resistor to ground in the emitter circuit.

As with both of the other configurations, the bias is set such that the transistor is turned on and passing a constant current that keeps it in its region of an almost linear relationship between small base current changes and larger collector current changes. With variation of the incoming signal and thus the  base current there is a corresponding change in the collector current dictated by the transistor’s gain, and thus an output voltage is generated across the emitter resistor. Unlike the common emitter amplifier this voltage increases or decreases in step with the input voltage, so the emitter follower is not an inverting amplifier.

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