Good in a Pinch: The Physics of Crimped Connections

I had a friend who was an electronics assembly tech for a big defense contractor. He was a production floor guy who had a chip on his shoulder for the engineers with their fancy book-learnin’ who couldn’t figure out the simplest problems. He claimed that one assembly wasn’t passing QC and a bunch of the guys in ties couldn’t figure it out. He sidled up to assess the situation and delivered his two-word diagnosis: “Bad crimp.” The dodgy connector was re-worked and the assembly passed, much to the chagrin of the guys in the short-sleeved shirts.

Aside from the object lesson in experience sometimes trumping education, I always wondered about that “bad crimp” proclamation. What could go wrong with a crimp to so subtly futz with a circuit that engineers were baffled? How is it that we can rely on such a simple technology to wire up so much of the modern world? What exactly is going on inside a crimped connection anyway?

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Review: Hammer-Installed Solderless Raspberry Pi Pin Headers

A few days ago we reported on a new product for owners of the Raspberry Pi Zero, a set of solderless header pins that had a novel installation method involving a hammer. We were skeptical that they would provide a good contact, and preferred to stick with the tried-and-trusted soldered pins. It seems a lot of you agreed, and the comments section of the post became a little boisterous. Pimoroni, the originator of the product, came in for a lot of flak, with which to give them their due they engaged with good humor.

It’s obvious this was a controversial product, and maybe the Hackaday verdict had been a little summary based on the hammer aspect of the story. So to get further into what all the fuss had been about I ordered a Pi Zero and the solderless pin kit to try for ourselves.

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Give Your Raspberry Pi A Good Hammering

One of the features of the Raspberry Pi Zero is that it arrives with no GPIO header pins installed. The missing pins reduce the price of the little computer, as well as its shipping volume. A task facing most new Pi Zero owners has therefore been to solder a set of pins into the holes, and indeed many suppliers will sell you the pins alongside your new Zero.

The British Pi accessories supplier Pimoroni think they may have a solution to this problem, with a set of solderless pins that the user is expected to fit by tapping both pins and Pi with a hammer. Each pin is designed to deform under pressure, and grip the through-plated walls of the hole in the PCB. In reality they are push-fit pins designed to be fitted with a press or a special tool, but since the average Zero buyer will have neither they supply a small laser-cut jig and give instructions to tap carefully with a pin hammer or similar. They have a demonstration as part of their regular Bilge Tank podcast, which we’ve included below the break.

Pins like these can be quite reliable when installed with the proper tools. They are often used in military and aerospace systems. In this case though, we expect that a chorus of you will be limbering up to comment that it would be far better to solder the connector, and we can’t help agreeing with you. Of course this product isn’t really marketed at Hackaday readers. Instead, the target market of a board like the Zero are children. For them soldering may well be a step too far. We can’t help wondering though whether hammer installation will deliver a reliable enough contact, and whether we’ll see a horde of youngsters whose Pi HATs don’t work due to dodgy connectors. Aside from the ones who’ve broken their Zeros with hammering that was a bit enthusiastic, that is.

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A Machine Shop in A Toolbox: Just Add Time

You don’t need any fancy tools. A CNC machine is nice. A 3D printer can help. Laser cutters are just great. However, when it comes to actually making something, none of this is exactly necessary. With a basic set of hand tools and a few simple power tools, most of which can be picked up for a pittance, many things of surprising complexity, precision, and quality can be made.

Not as pretty, but worked just the same.
Not as pretty, but worked just the same.

A while back I was working on a ring light for my 3D printer. I already had a collection of LEDs, as all hackers are weak for a five-dollar assortment box. So I got on my CAD software of choice and modeled out a ring that I was going to laser cut out of plywood. It would have holes for each of the LEDs. To get a file ready for laser cutting ook around ten minutes. I started to get ready to leave the house and do the ten minute drive to the hackerspace, the ten minutes firing up and using the laser cutter (assuming it wasn’t occupied) and the drive back. It suddenly occurred to me that I was being very silly. I pulled out a sheet of plywood. Drew three circles on it with a compass and subdivided the circle. Under ten minutes of work with basic layout tools, a power drill, and a coping saw and I had the part. This was versus the 40 minutes it would have taken me to fire up the laser cutter.

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Fail Of The Week: My 3D Printer Upgrade

After years of cutting my hands on the exposed threads of my Prusa Mendel i2, it was time for a long overdue upgrade. I didn’t want to just buy a new printer because it’s no fun. So, I decided to buy a new frame for my printer. I settled on the P3Steel, a laser cut steel version of the Prusa i3. It doesn’t suffer from the potential squaring problems of the vanilla i3 and the steel makes it less wobbly than the acrylic or wood framed printers of similar designs.

My trusty i2. Very sharp. It... uh.. grew organically.
My trusty i2. Very sharp. It… uh.. grew organically.

I expected a huge increase in reliability and print quality from my new frame. I wanted less time fiddling with it and more time printing. My biggest hope was that switching to the M5 threaded screw instead of the M8 the i2 used would boost my z-layer accuracy. I got my old printer working just long enough to print out the parts for my new one, and gleefully assembled my new printer.

I didn’t wait until all the electronics were nicely mounted. No. It was time. I fired it up. I was expecting the squarest, quietest, and most accurate print with breathtakingly aligned z-layers. I did not get any of that. There was a definite and visible ripple all along my print. My first inclination was that I was over-extruding. Certainly my shiny new mechanics could not be at fault. Plus, I built this printer, and I am a good printer builder who knows what he’s doing. Over-extruding looks very much like a problem with the Z-axis. So, I tuned my extrusion until it was perfect.

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Thor’s Hammer Build Recognizes Its Master’s Hand

electromagnetic-thors-hammerOnly those who have completely insulated themselves from modern pop culture will miss the meaning of a Mjolnir build. It is, of course, the mythical hammer wielded by Thor, and only Thor. It’s a question of being worthy; a question solved perfectly by this electromagnetic Mjolnir build.

Using an electromagnet is smart, right? Just plunk the thing down on something metal (that is itself super-heavy or well-anchored) and nobody will be able to pick it up. It starts to get more interesting when you add a fingerprint reader, allowing only Mjolnir’s Master to retrieve it from atop a manhole cover.

But for us the real genius in the build is that the hammer isn’t burning power from the four 12V batteries most of the time. All of the people in the video below could have picked up the hammer had they first nudged it off the metal plate with their foot. The build uses a capacitive touch-sensor to enable and disable the microwave over transformer used as the electromagnet. An engineering trick like this really separates the gods from the posers.

We hate to admit it, but this is probably a cooler build than the Telsa-Coil powered Mjolin that [Caleb] built a few years back. Still, his held up as the best for many years, and if you’re going to be displaced this really is a build worthy of the new title: coolest Mjolnir hack.

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Hackaday Links: April 20, 2014

hackaday-links-chain

[Josh] hit the same issue we’ve faced before: cable modems don’t match a form factor and usually don’t make themselves easy to mount on something. We could complain about routers as well, but at least most of those have keyhole slots so you can hang them on some screws. Inspiration struck and he fabricated his own rack-mount adapter for it. Velcro holds it in place, with a cutout bezel to see the status lights and an added fan to keep things cool.

Here’s a pair of strange but possibly interesting ones that were sent in separately. The first is an analysis of how much energy short-run CNC prototyping consumes versus traditional manufacturing. The other is an article that [Liz] wrote about getting started with CNC mill bits. She says she compiled all that she learned as she was getting started in the field and wants to save others the effort.

This one goes back several years, but who doesn’t love to hear about a voice-controlled wheelchair?

So you can solder QFN parts but you can’t hammer a nail straight into a piece of wood? The answer, friend, is a laser guided hammer. Someone hire this [Andybot] person, because the solution to the problem shows the ability to out-think an interesting dilemma: how do you put a laser in a hammer head and still use it to hit things?

We’ve seen a lot of these long-range WiFi hacks over the years. This one is worth looking at because of the work done to create an outdoor mount that will stand the test of time.

And finally, we’re still really fond of this 2-bit paper processor that helps you wrap your brain around what’s going on with those silicon wafers that rule our everyday lives. [glomCo] liked it as well, and actually coded an emulator so that you can play with it without printing anything out on paper. We think it takes away some of the fun, but what an excellent programming exercise!