Hackaday Links: September 15, 2013

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First a quick announcement. We changed our “Kickstarter” category to “Crowd Funding“. We get a huge number of tips about crowd funding projects. We’re always interested in details. If you’re trying to get your crowd funding campaign on our front page make sure you’ve shared as many gritty project details (development process, problems/successes along the way, etc.) as possible . We usually prefer if this is done in a separate blog post from the campaign page itself.

Here’s a peephole hack that purportedly cost four grand. It uses a full on DSLR for the peephole hardware. Add a motion sensor and maybe you’ll be able to learn the faces of the neighbors who live on your floor. [via Gizmodo]

[Matthias] tells us that support for Rigol DS1052E oscilloscopes has been included in the 3.11 version of the Linux Kernel. Prior to this, getting the hardware to work on Linux was a hack, and a buggy one at that. For what it’s worth, here’s confirmation that support was added.

A post about reverse engineering the FitBit Aria Wi-Fi scale was sent in by [Christopher]. This makes us wonder if you could patch into a digital scale, using your own electronics to spoof the FitBit version?

We always keep our paperboard six-pack carriers so that we have a way to transport our homebrew beer. But rolling into a party with this laser-cut beer caddy which [Daniel] designed looks a lot cooler.

Texas Instruments has an MSP430 Selection Guide (PDF) which we found interesting. The first nine pages or so are pretty much just marketing, but several pages of parametric tables found after that make for a great collection of data on the hardware families. [via Dangerous Prototypes]

[Antoine] spared no expense building a coffee table that showcases his old motherboards. The illuminated glass and wood art piece rang in at around $400 in materials. We’re a little more minimalist with our home decor. We still want something along the lines of this LED matrix version.

Speaking of LED matrices, [Mario] dropped off a link to his LED Space Invaders game in the comments of last week’s Game of Light post. What we can’t figure out is why so many people hesitate to send in a tip about their awesome projects?

Adding a display to a USB digital scale

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[Oleg] found himself in possession of a Stamps.com Model 510 5lb digital scale.  It’s a great scale, but only works as a USB HID device. In other words, it’s a digital scale without a digital display. He decided he wanted it to be more standalone, so he added a Toshiba HD44780 (compatible) display. An Arduino UNO and USB Host shield were used to make it happen. His sketch simply polls the scale and outputs the weight on the display.

In this case, he used the USB Host Shield from Circuits at Home, but a brief look shows they use the same MAX3421 controller chip as Sparkfun and other versions of the board. You might also be able to pull off the same functionality with an AVR running V-USB, though admittedly it wouldn’t be so easy.

We haven’t found a great way to add USB host mode to projects other than shields like the one [Oleg] used. If you know of a better way, share your ideas in the comments.

Of course, if this isn’t hardcore enough for you, forget using a consumer scale – make your own from scratch!

Building a digital scale from scratch

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[Raivis] was given a particular task at his university – find a way to measure how many Duplo bricks are stacked together. There are a number of ways to do this, everything from computer vision to using a ruler, but [Raivis] chose a much more educational method. He built a digital scale from scratch out of a strain gauge and a Wheatstone bridge. The build log is immensely educational and provides some insight into the challenges of weighing things digitally.

A strain gauge is a simple piece of equipment, just a small force sensitive resistor. When attached to a metal bar and a force is applied, the resistance inside the strain gauge changes, but not by much. There’s only a few micro Ohms difference between the minimum and maximum of [Raivis]’ load cell, so he needed a way to measure very slight changes in resistance.

The solution was a Wheatstone bridge, or four resistors arranged in a square. When one of the resistors in the bridge is replaced with a strain gauge, very small changes in resistance  can be measured.

With a custom ‘duino amplifier shield, [Raivis] can measure the resistance of his load cell with 10-bit resolution, or a maximum weight of 1.32 kg with a resolution of two and a half grams. A single duplo block weighs about 12 grams, so we’ll call this one a success.

Bakery automation mixes single cookies

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[Ben Krasnow’s] latest project is a delicious one. In the image above he’s showing off the beginnings of his cookie dispenser. No, it’s not another take on a way to eat Oreo cookies. It actually comes much earlier in the production chain. His device is akin to a 3D printer for baked goods in that it will be able to automatically combine raw ingredients to form production runs as small as a single serving of cookie dough.

When we first heard about it we wondered why you would want to bake just one cookie? But of course that’s not the purpose at all. The machine will allow you to bake a full sheet of cookies, but provides the option of making each one of them with a different recipe. As with all baking, combining ingredients in the proper proportions is paramount. In the post linked at the top he’s working on a butter dispenser. But in an earlier post he hacked an electronic scale to help weigh other ingredients. You can watch both video clips after the break.

Imaging a dozen cookies with slightly different amounts of flour in them. A few test sheets and he should be able to dial in the very best recipes.

Continue reading “Bakery automation mixes single cookies”

Kitchen scale key transplant

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[Markus] is quite happy with his kitchen scale. It’s one of the tools he uses most frequently when cooking. But recently the button has begun to give him problems. He figures the years of spilling a little bit of this and that has mucked up the contacts. His solution was to bypass the button using a Cherry MX switch.

Really any replacement should do since the switch merely completes an electrical connection. But there’s a subset of hackers who swear by the Cherry MX switches that come in some keyboards. [Markus] had just such a keyboard on hand, which he was already using for parts, so he pulled out the switch and cut a hole in the scale’s case where he could mount it. After temporarily super gluing the switch in place he completed the task by filling the gap on the outside with hot glue, then running another bead of it along the inside. The addition of the ‘T’ key finishes the hack. The plastic key is easy to clean and will help shed flour, oil, or anything else he might spill during his culinary adventures.

This hack was fast and easy and may have convinced [Markus] to roll his own controller board for the device. We’ll keep a lookout for a follow-up post detailing those alterations.

Firing rocket engines in the wrong direction — this is only a test

LVL1 has a new rocketeering group. This rocket engine testing platform is the first project to come out of the fledgling club. The purpose of the tool is to gather empirical data from model rocket engines. Having reliable numbers on thrust over time will allow the team to get their designs right before the physical build even starts.

The rig uses a pine base, with a PVC frame, threaded bolts, and a PVC cuff for mounting the engine in place. It is set to fire up in the air, directing the thrust down onto a scale. The flex sensor in the scale is monitored by an Arduino, and should be able to hold up to the 5000 pounds grams of thrust max which this type of engines can put out. The data is pushed via USB to a laptop computer where it is stored in a spreadsheet.

Calibration would be an issue here. But as long as they’re always using the same strain sensor the numbers will be accurate enough relative to each other.

Connecting a dumb scale to your smartphone

[Casainho] wanted to track his body weight using an app on his Android phone. He just needed a way to get the weight readings onto the device automatically. He ended up adding Bluetooth to a bathroom scale and hacking the app to grab data from it.

The scale which he hacked is a digital model, which makes it possible to read the weight data if you know what you’re doing. [Casainho] already completed a weight logging scale hack which stored the data on an SD card. So this was a recreation of that project but with a Bluetooth module for the output rather than the card for storage.

Now you can buy WiFi enabled scales, but that’s not nearly as fun as a hack like this. Plus one of those will cost you around $200 and the hardware for this version came it at only $75. It includes an LPC2103 dev board, $6 Bluetooth module, character display, batteries, and misc. supplies. The software end of the hack was helped greatly by the fact that the Android apps which [Casainho] is using are both open source.