Home Made Diodes From Copper Oxide

May 1, 2016 by 31 Comments

We’re all familiar with semiconductor devices, and we should remember the explanation from high-school physics classes that they contain junctions between two types of semiconductor material. “N” type which in the for-schoolchildren explanation has a surplus of electrons, and “P” type which has “Holes”, or a deficit of electrons.

Unless our careers have taken us deep into the science of the semiconductor industry though that’s probably as close as we’ve come to the semiconductors themselves. To us a diode or a transistor is a neatly packaged device with handy wires. We’ve never really seen what’s inside, let alone made any real semiconductor devices ourselves.

[Hales] though has other ideas. With the dream of creating a paintable semiconductor layer for ad-hoc creation of simple diodes, he’s been experimenting with oxidising copper to make a surface of cupric oxide onto which he can make a contact for a simple diode.

What makes his experiments particularly impressive though is not merely that he’s created a working diode, albeit one with a low reverse breakdown voltage. He’s done it not in a gleaming laboratory with a full stock of chemicals and equipment, but on his bench with a candle, and drops of water. He takes us through the whole process, with full details of his semiconductor manufacture as well as his diode test rig to trace the device’s I/V curve. Well worth a read, even if you never intend to make a diode yourself.

We’ve featured a cuprous oxide diode once before here at Hackaday, albeit a rather fancier device. If this article has piqued your interests about diodes, may we direct you to this informative video on the subject?

The diode looks black, leading me to believe it’s cupric oxide and not cuprous oxide. Feel free to argue that point in the comments anyway – Ed.

Precision CNC With Epoxy Granite

May 1, 2016 by 28 Comments

Epoxy granite is an overlooked material when it comes to making home CNC builds. As far as time and money goes, when you add in all the equipment it comes out cheaper than an aluminum casting set-up. Epoxy granite has mechanical properties better than cast iron, increased dimensional stability, better vibration damping, and looks awesome when done right. Also, you can cast precision surfaces and threaded holes into your design, which is pretty cool.

In these two videos by [Jørgen Hegner] we get to watch him and a friend make a matching set of precision CNC machines. It’s built in a similar style to other nice builds we’ve featured. This way of making it needs a bigger footprint than a gantry mill and can’t be built as large. However, it solves a lot of mechanical issues and squaring with the gantry design while not being as difficult to get right as a box or knee mill.

After casting they machined the material embedded in the granite to mount the ways. The ways are linear bearings and ball screws. Expensive, but as the footage shows, very accurate.  The rest of the machine is assembled and tuned. Then it gets installed in a home made 80/20 enclosure. We really like the LCD panel that’s incorporated into the front shield of the machine. They really went all out with the CNC control panel. It looks like they can do anything from jog the axis to monitor and control the water cooling for the spindle.

It appears that all the precision work is put to good use as there are some shots at the end of video two of a beautiful clock CNC’d on this machine. Videos after the break.

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Minimal 433 MHz Web Home Automation

May 1, 2016 by 4 Comments

How minimal can a decent home automation setup be? If you need an HTML frontend, you’re going to need a webserver. An ESP8266 will do the trick. And then you need to be able to control your electronics. The cheapest and easiest way to do that is with the ubiquitous 433 MHz remote-controlled outlets and a $1 radio unit from an online auction site. Add in a cheap ESP8266 module, and your total outlay is going to be under $20.

That’s exactly what [Nikos Kantarakias] did. He combined a bunch of available ESP8266 Arduino libraries — one for driving the 433 MHz radio modules, [Paul Stoffregen]’s libraries for keeping time and for setting alarms, and another for keeping track of time zones — with some of his own code for setting up WiFi access, and it’s done.

It’s all available on GitHub for your perusal. The code does some strange things — like requiring a complete reboot every time you set an alarm — but it does let you set recurring and one-off activations of the attached devices with a web interface that’s served off the ESP8266 itself. If you want your coffee machine to turn itself on in the mornings, and want a system that’s easy for the other inhabitants of your house to configure, something like this might be just the ticket.

But if you’re looking for a project on the other end of the ESP-tech spectrum, [CNLohr] wrote a standalone Ethernet controller for the thing. Woah.

Has Mankind Gone Too Far With Drone Fishing?

May 1, 2016 by 64 Comments

Previously man was limited in his ability to fish the waters of this world by the power of his arm or his ability to procure the services of a boat. Now, as long as man is willing to risk a thousand dollar drone set-up, he can descend upon unsuspecting fish with robotic precision. It is very unfair, and awesome.

The concept is simple. Buy one of those drones every upper middle class teenager seems to get for Christmas. Attach a streaming camera set-up to it. Next, rig it up so that it can fly the fishing line from the rod out, but when the fish bites the line can easily detach. Finally, attach a friend to the controls of the fishing rod.

After that it’s like shooting fish in an ocean. Fly the drone around, pulling the line behind you, until you see a school of fish. Next, dangle the bait in the center of the school. Inevitably one will strike, the line will detach, and it’s up to your friend to reel in your catch. Either that or a bunch of tuna will wreck your drone and you’ll get to watch a livestream of a thousand dollars sink to the ocean floor. Video after the break.

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Lint And Dog Hair Supercapacitor

April 30, 2016 by 27 Comments

[Mechanicus] has made a supercapacitor with a claimed 55 Farads per gram of active material. And he’s made it using dryer lint and dog hair. And he’s done it in 24 hours. That’s the short story. The longer story is an epic journey of self-discovery and dog ownership, and involves a cabin in the Wyoming backwoods.

So how did he do it?

He started with a home-made crucible that you maybe wouldn’t want to carry around in public as it bears more than a passing resemblance to a pipe bomb. Into that he packed his dog hair and lint, along with a generous helping of ammonia. An hour or two in a woodstove glowing red, and he’d made a rod of mostly carbon with the required high surface area. He sawed off a carbon slice, bathed it in lithium sulphate and potassium iodide electrolyte, and with the addition of a couple of pieces of stainless steel he had a supercapacitor.

Full details of his build can be found on the hackaday.io pages linked above, but there is also a handy YouTube video below the break.

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Re-Capping An Ancient Apple PSU

April 30, 2016 by 35 Comments

It sometimes comes as a shock when you look at a piece of hardware that you maybe bought new and still consider to be rather high-tech, and realise that it was made before someone in their mid-twenties was born. It’s the moment from that Waylon Jennings lyric, about looking in the mirror in total surprise, hair on your shoulders and age in your eyes. Yes, those people in their mid-twenties have never even heard of Waylon Jennings.

[Steve] at Big Mess o’Wires has a Mac IIsi from the early 1990s that wouldn’t power up. He’d already had the life-expired electrolytic capacitors replaced on the mainboard, so the chief suspect was the power supply. That miracle of technology was now pushing past a quarter century, and showing its age. In case anyone is tempted to say they don’t make ’em like they used to, [Steve]’s PSU should dispel the myth.

It’s easy as an electronic engineer writing this piece to think: So? Just open the lid, pop out the old ones and drop in the new, job done! But it’s also easy to forget that not everyone has the same experiences and opening up a mains PSU is something to approach with some trepidation if you’re not used to working with line power. [Steve] was new to mains PSUs and considered sending it to someone else, but decided he *should* be able to do it so set to work.

The Apple PSU is a switch-mode design. Ubiquitous today but still a higher-cost item in those days as you’ll know if you owned an earlier Commodore Amiga whose great big PSU box looked the same as but weighed ten times as much as its later siblings. In simple terms, the mains voltage is rectified to a high-voltage DC, chopped at a high frequency and sent through a small and lightweight ferrite-cored transformer to create the lower voltages. This means it has quite a few electrolytic capacitors, and some of them are significantly stressed with heat and voltage.

Forum posts on the same PSU identified three candidates for replacement – the high voltage smoothing capacitor and a couple of SMD capacitors on the PWM control board. We’d be tempted to say replace the lot while you have it open, but [Steve] set to work on these three. The smoothing cap was taken out with a vacuum desoldering gun, but he had some problems with the SMD caps. Using a hot air gun to remove them he managed to dislodge some of the other SMD components, resulting in the need for a significant cleanup and rework. We’d suggest next time forgoing the air gun and using a fine tip iron to melt each terminal in turn, the cap only has two and should be capable of being tipped up with a pair of pliers to separate each one.

So at the end of it all, he had a working Mac with a PSU that should be good for another twenty years. And he gained the confidence to recap mains power supplies.

If you are tempted to look inside a mains power supply you should not necessarily be put off by the fact it handles mains voltage as long as you treat it with respect. Don’t power it up while you have it open unless it is through an isolation transformer, and remember at all times that it can generate lethal voltages so be very careful and don’t touch it in any way while it is powered up. If in doubt, just don’t power it up at all while open. If you are concerned about high voltages remaining in capacitors when it is turned off, simply measure those voltages with your multimeter. If any remain, discharge them through a suitable resistor until you can no longer measure them. There is a lot for the curious hacker to learn within a switch mode PSU, why should the electronic engineers have all the fun!

This isn’t the first recapping story we’ve covered, and it will no doubt not be the last. Browse our recapping tag for more.

Is It A Stepper? Or Is It A Servo?

April 30, 2016 by 37 Comments

Almost everyone who is involved with 3D printing thinks to themselves at some point, “this could all be done using a closed-loop system and DC motors”. Or at least everyone we know. There’s even one commercial printer out there that uses servo control, but because of this it’s not compatible with the rest of the (stepper-motor driven) DIY ecosystem.

[LoboCNC] wanted to change this, and he’s in a unique position to do so, having previously built up a business selling PIC-based servo controllers. His “servololu” is essentially a microcontroller and DC motor driver, with an input for a quadrature encoder for feedback. The micro takes standard step/direction input like you would use to drive a stepper motor, and then servos the attached DC motor to the right position. It even signals when it has an error.
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