A Salinometer Built For The Science Olympiad

January 9, 2012 by 13 Comments

This is a Digital Salinometer which [Daniel Kramnik] built as a Science Olympiad entry. He’s a Junior in High School and when looking for a project to enter into the Water Quality event he was interested in achieving greater accuracy than a mechanical hydrometer provides.

We think the circuit design is very impressive for anyone who hasn’t complete formal training as an engineer, and outstanding for someone as young as [Daniel]. Measurements depend on two main parts, a temperature control and a salinity sensor. These are both necessary because fluctuation in sample temperature will affect the salinity reading.

A Peltier element is used to heat the water sample if it doesn’t fall within a set range of temperatures. From there, an Op-Amp circuit conditions a signal running through the sample, passing an output to the ADC converter chip which drives the three-digit readout. [Daniel] calculates an accuracy within 0.0014%. He must be on the mark because he’s won his regional competition and will soon compete at the state level.

The Matrix Reloaded: Now Better Than The Movie

January 9, 2012 by 34 Comments

If you’re looking for a custom controller for a MAME cabinet build, CNC machine, or just want to control a robot build, you’re going to need to wire up some buttons. You could wire up a bunch of buttons to a microcontroller, but if you use an old computer keyboard the work is already done for you.

[Rupert] sent in a great tutorial on repurposing old keyboards. The build is very, very simple: just take a multimeter to each contact and measure the rows and columns for continuity. Once [Rupert] had the matrix codes for every button on the keyboard, he wired up a length of ribbon cable to the keyboard PCB. From there, a small breakout board provides all the connections that a MAME cabinet would need.

Opposed to a custom keyboard encoder like an I-PAC or a homebrew solution, [Rupert]’s build is very easy and can be built for only the dignity required to dumpster dive for a keyboard.

Projector Project Bears No Fruit But It Was A Fun Ride

January 9, 2012 by 18 Comments

No matter how good the intentions or how strong your hack-fu may be, sometimes you just can’t cross the finish line with every project. Here’s one that we hate to see go unfinished, but it’s obvious that a ton of work already went into reclaiming these smart white-board projectors and it’s time to cut the losses.

The hardware is a Smartboard Unifi 35″ computer with a projector mounted on a telescoping rod. It was manufactured for use with a touch-sensitive white board which the guys at the Milwaukee Makerspace don’t have. The projector works, but all it will display is a message instructing the user to connect the computer to the white board. Since they’ve got a couple of these projectors, it would be nice to salvage the functionality.

The first attempt was to replace the video signal to the projector. A few test boards were etched to experiment with DVI input. This included several logic sniffing runs to see what the computer is pushing to get the warning message to display. Alas, the group was not able to get the device to respond. But this opens up a great opportunity for you to play Monday morning hacker. Take a look at the data they’ve posted in the link above and let us know how you would’ve done it in the comments.

DIY Fresnel Reflector

January 9, 2012 by 14 Comments

Just like destroying an ant colony with a magnifying glass, there’s nothing like cooking hot dogs and roasting marshmallows with a nice parabolic reflector. Of course covering an old satellite dish with mylar or aluminum tape doesn’t take much skill, however cool it is. [Uwe] came up with a much more technical means of building a Fresnel reflector that will cook your hot dogs in seconds, but only on sunny days.

[Uwe] channeled a little bit of [Apollonius] when he realized that a flat cardboard ring with a section removed could be joined together into a conic section. The resulting section looks just like one concentric ring in a Fresnel reflector. [Uwe] wrote a small program in Visual Basic to calculate the necessary diameter and angle of his conic sections.

A bit of cardboard was cut out and pieced together with some very reflective aluminum tape. The resulting Fresnel reflector concentrates 117 times the normal solar radiation onto a small point. It’s more than enough to burn holes in construction paper, but we’ll be using a microwave for our lunch today.

Got Dead Bugs In Your Stereo?

January 9, 2012 by 44 Comments

It happens to the best of designers, spending untold amounts of time designing a complex device just to find out that you missed a trace, or you couldn’t rout something to something else. As time marches on its becoming a bit less common to pop open a commercially produced device and see a little jumper wire or 2 flying across a pcb, or a resistor straddling an IC.

But when [Ilektron] opened up a Yamaha Dolby Pro Logic receiver to scavenge for parts he saw a very big “oops” and a even wilder fix. The maker took a pair of relays, flipped them “belly up” and hot glued them into place on top of a pair of ICs. Then the mess was “dead bug” wired to the circuit using insulated and uninsulated bus wire, contacts were then reinforced / insulated using more hot glue.

This is one of the most hacky fix we have seen in a commercially produced product, but we would love to hear your amusing horror stories of “WTH did they do?” So join us in the comments after the break.

Programming AVR I2C Interface

January 9, 2012 by 8 Comments

I2C as many of you know, is a simple serial interface for many peripheral devices to micro controllers, but it can quickly become confusing to people who may not be accustom to it. Because of that, I2C tutorials are always welcome, and this new tutorial by [Embedds] does an excellent job of how to use I2C with an AVR with a 24C16 2Kbyte EEPROM.

The first half of the tutorial provides a clear explanation of how I2C works, including its signal structure, addressing, and data packets. It then moves on to AVR territory showing how to setup the I2C in an AtMega micro controller. The author uses a pretty standard to most of us Arduino, with software written in AVR C and a nifty little GUI programming application which eases the hassle of dealing with AVRDude directly.

Plenty of code samples follow from twiddling registers to a full blown application reading and writing bits from the EEPROM to a serial terminal on a PC.

[Alex] Shows Us What Happens When Dance Dance Revolution Meets Simon

January 8, 2012 by 5 Comments

ddr-simon

[Alex] was digging through his closet and came upon an old PS2 game pad for Dance Dance Revolution. He hated the idea of throwing it out just slightly more than the idea of playing DDR again, so he decided to find a way to reuse it.

He was a big fan of the game Simon (aka Genius) as a kid and thought that the DDR pad would make a novel interface for the classic game. Using the PS2XLib by [Bill Porter], which allows an Arduino to easily communicate with a PS2 controller, [Alex] put his Simon replica together in no time flat.

He painted an empty ice cream container with the classic Simon colors, installing a small LED under each quadrant, then wrote the game’s code.

As you can see in the video below, his version of the game works nicely, and forces you to actually get up and move a bit, which we like.

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