Hackaday Links: December 25, 2011

Ah, Christmas. That wonderful time of year when you can roll out of bed to the screams and wails of children, grab a hot cocoa, and spend several hours arguing with an 8-year-old about which LEGO set to build first. Simply magical. While you’re waiting for the Doctor Who Christmas special to come on, settle down with these wonderful Christmas-themed builds that came in over the last few weeks.

One step closer to Robot Santa

Here’s an interesting way to spice up your seasonal headwear. [Mark] took a Santa hat and added a string of multicolored LEDs to the brim. The lights were picked up at a drug store for a dollar. Control is through a simple push button connected to an ATtiny13. Press the button, the lights cycle in a different pattern. Very cool, so check out the video.

A holographic holiday tree

[Auger] posted this very cool light up Christmas tree decoration on Instructables. This tree is made up of three pieces of acrylic. Different designs were laser cut into each piece of plastic – candy canes for the ‘red’ piece, stars and tinsel for the ‘yellow’ piece, and the tree for the ‘green’ piece. LEDs of the respective colors are cemented to the bottom of each bit of plastic. It’s called light piping and is used everywhere. This is the first time we’ve seen three colors, though.

This is what nerds do, and it’s awesome

[Rickard Dahlstrand] was playing around with his phone trying to take deliberately fuzzy pictures of his tree. He noticed the dashes produced from the LED Christmas lights must be produced from PCM dimming. Going through the EXIF data in the picture, he found the exposure time was 1/17th of a second. 1/17 of a second = ~ 58 ms / 5 (cycles on the picture) = ~11 ms per cycle = ~100 Hz frequency on the PCM dimming. Of course this is just about 2 times the line frequency in [Rickard]‘s native Sweden, so we’ll call this confirmed. There’s no blog post for this, but we’ve never seen a clearer example of applied geekery. Simply awesome.

Yeah, we measured [Rickard] on a nerd meter

In the spirit of giving, [Johannes] decided to tell the entire world exactly how nerdy he is. He built a ‘Nerd Alert’ meter out of an old 1950s Japanese multimeter. The old guts of the meter were chucked, and a simple amp made out of a transistor amplifies the current flowing through the user’s fingers. A neat scale ([Johannes] measures somewhere between Amiga Workbench and Space invaders) replaces the old, boring, number-based one. Again, no write-up, but here’s some awesome build pictures.

Finally a use for all those old radio tubes

[AUTUIN] took apart a vacuum tube with a blow torch and a diamond cutting wheel. Surprisingly, he was able to put it back together, but not before making a wonderful Christmas ornament. There are two copper wires inside the envelope that are the leads to a single orange-red LED. The whole thing is powered by a watch battery. We’ll be sure to reference [AUTUIN] next time we have to take apart a glass bulb, because he managed not to burn, cut or blind himself.

Six things in a links post? It’s a Christmas miracle!

[Darryl] sent in a nice tool to select and display all of the hacker/maker merit badges available from Adafruit. Oh, we’re still trying to figure out who to give 10 badges to. We’re giving away skull ‘n wrench badges to the top ten hacks ever featured here. Leave a note in the comments, or tell us who should win.

Holiday wishes

Now put the computer down and go spend some time with your families, or failing that, strangers. Of course there’s an all day Doctor Who marathon, and that thing isn’t going to watch itself…

Adding RS232 to a multimeter the hard way

You might want to store information from a multimeter to be graphed over time. This comes with pretty much all of the high-end professional models. But if you buy a super cheap meter you can bet this isn’t an option. [Jazzzzzz] has found a way to pull the data from a $4 meter via RS232. It’s not impossible, but we definitely think he’s doing it the hard way. That’s because he’s not just tapping into a dormant feature. He’s actually adding a microcontroller to sample the data and push it via the RS232 protocol.

On the bright side, this is easier than building a multimeter from scratch. The sampling circuits are still being used, with a PIC 16F688 intercepting the signals as they enter the stock microcontroller. The signal he was after comes into the chip on just one pin, but to get the readings right on the PIC he had to use an OpAmp. That’s only part of the puzzle as he also needed a way to tell what the selector switch was set at. In the end, adding a potentiometer and reading its value let him calculate the position.

[Thanks Karl]

Adding auto-off to a cheap multimeter

[Florin] picked up a cheap multimeter in order to make multiple measurements at one time. Unfortunately, he wasn’t very good at remembering to turn it off when he was finished so he burned through some batteries. Why an auto-off feature wasn’t the first thing coded into the firmware we’ll never know, but [Florin] developed his own hardware-based auto-off circuit.

It sounds like he had all of the components necessary for this on hand already. He grabbed an AVR ATtiny25 in a surface mount package. To keep the board small, he didn’t include an ISP header, but instead made long pads that could have wires soldered to them for flashing the firmware. The microcontroller drives an NPN transistor that can cut off the ground path between the multimeter and its battery. A tactile switch is connected to one of the external interrupt pins and, when pressed, gives you 15 minutes of time to use the meter. After that, the chip kills the power and goes into sleep mode. Simple, and small enough to fit inside the case.

[via Dangerous Prototypes]

Hackaday Links: Tuesday, July 19th

Here’s another “useless machine” variant.  The trick to this one is that it has dual “fingers” and can work either way. Which way it turns off is selectable via a switch on the side, and the fingers can both be turned on to “fight” each other. Check out the video here.

This video depicts the assembly of a Gameboy MAME-style cabinet. For those wanting to try something like this, this video may fill you in on some of the required assembly techniques, such as how to put decals on the side of your cabinet.

This video featuring the “Autonomous Ultimate Wall-E” shows this robot’s navigational skills around the house.  Additionally, it has some nicely actuated arms.

The Verbalizer is a microphone designed to be used with Google’s voice search. It’s also designed with Arduino compatibility in mind and is open-source. Could be a good tool for your next hack.

These clever multimeter probes were built using pogo pins used in electrical test equipment. The springs inside of these pins help keep them planted firmly on the test point in question and reportedly gives a very good connection.

Lego Minifig multimeter makes resistor sorting a lot more fun

lego_minifig_multimeter

While there’s typically not much room on our work bench for toys, [David] over at Robot Room has put together a pretty cool multimeter for which we would make an exception.

His Lego Minifig multimeter is constructed using mostly standard off-the-shelf Legos, and a pair of Minifigs he modified to suit his needs. Translucent Minifig heads were sourced online to allow the neck-mounted LEDs to shine through, and each of the bodies were drilled out in several places to accommodate the wires he uses to take measurements.

The multimeter will display the resistance of any item from 10 – 10,000,000 Ω, as well as measure the voltage of any battery you can manage to fit under the Minifig’s metal wrench. The multimeter takes measurements using an ATmega168, and relays that data through a serial to USB converter connected to a nearby computer. The computer is host to a .NET application he wrote which displays and speaks both the resistance and voltage values.

Keep reading to see a quick video walkthrough and a demonstration of the multimeter at work.

[Read more...]

Make presents: The Multimeter

This video falls under the category of things we want to send people when they ask “how do I get started with electronics”, and we get asked that a lot. For those of you who have been working with electronics for years at all, you can skip this entire video. That is, unless you really want to watch an instructional video on multimeters. In the video, which we’ve included after the break, they talk about the differences between different meters, the common uses and how to actually use the meter to get the results you need. Stuffed full of useful information, this video will get those of you who are still reading up to snuff pretty quickly. Now go use your multimeter to do some hacking!

[Read more...]

Building a spectrophotometer

What can you make with a toilet paper roll, duct tape, and a graphing calculator? A stand for your homemade spectrometer. This is neither as pretty nor as accurate as a precision scientific instrument, but that doesn’t mean it’s useless. In fact, it works perfectly well for rudimentary observations. Light is shined through a sample solution, passes through a diffraction grating, then shows up as bands of color on the projection surface seen above. The photosensor mounted on the cardboard tube was pulled from a night-light, and is read using the ruler and the multimeter. This results in two data units that are used to graph the results. As long as you’re running test samples as a control this simple setup will yield useful information for the scientist on a shoe-string budget.

[via BoingBoing]

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