Reverse Engineering a Bathroom Scale for Automated Weight Tracking

Bathroom Scale

[Darell] recently purchased a fancy new bathroom scale. Unlike an average bathroom scale, this one came with a wireless digital display. The user stands on the scale and the base unit transmits the weight measurement to the display using infrared signals. The idea is that you can place the display in front of your face instead of having to look down at your feet. [Darell] realized that his experience with infrared communication would likely enable him to hack this bathroom scale to automatically track his weight to a spreadsheet stored online.

[Darell] started by hooking up a 38khz infrared receiver unit to a logic analyzer. Then he recorded the one-way communication from the scale to the display. His experience told him that the scale was likely using pulse distance coding to encode the data. The scale would start each bit with a 500ms pulse. Then it would follow-up with either another 500ms pulse, or a 1000ms pulse. Each combination represented either a 1 or a 0. The problem was, [Darell] didn’t know which was which. He also wasn’t sure in which order the bits were being transmitted. He modified a software plugin for his logic analyzer to display 1’s and 0’s on top of the waveform. He then made several configurable options so he could try the various representations of the data.

Next it was time to generate some known data. He put increasing amounts of weight on the scale and recorded the resulting data along with the actual reading on the display. Then he tried various combinations of display settings until he got what appeared to be hexadecimal numbers increasing in size. Then by comparing values, he was able to determine what each of the five bytes represented. He was even able to reconstruct the checksum function used to generate the checksum byte.

Finally, [Darell] used a Raspberry Pi to hook the scale up to the cloud. He wrote a Python script to monitor an infrared receiver for the appropriate data. The script also verifies the checksum to ensure the data is not corrupted. [Darell] added a small LED light to indicate when the reading has been saved to the Google Docs spreadsheet, so he can be sure his weight is being recorded properly.

Mutant Kitchen TV Computer

mutant-kitchen-computer-and-tv

In need of a kitchen entertainment system, [BoaSoft] headed to the parts bin and produced a project that can easily be called a mutant. That being said, we love the results!

Here’s the link to the original Russian language post. If your Russian is a bit rusty here’s a really awful machine translation. So let’s see if we can decipher this hack.

Sounds like [BoaSoft] had a broken Acer laptop on hand. Problem was the laptop can’t play over-the-air television (and similarly, a television can’t surf the net). The solution was to figure out how to utilized a TV tuner of unknown origin, combine that with the laptop and a computer monitor, then add back all the user interface you’d expect from an entertainment device.

The board shown in the first post of the thread is familiar to us. It seems to be based on the IgorPlug board which is a hack that goes waaaay back. This allows for the use of an IR media center remote and those input signals are easy to map to functions. The computer runs Windows Media Center which is already optimized for remote control but can use a wireless keyboard and mouse when more computer-centric functions are necessary.

With all on track the rest of the hack deals with hacking together a case. The laptop’s original body was ditched for some extended sides for the back of the monitor. [BoaSoft] did a great job of installing all the necessary ports in these extensions. Once in the kitchen everything is nice and neat and should stand the test of time.

[Thanks Dmitry]

SMT and Thru-Hole Desoldering

My introduction to electronic manufacturing was as a production technician at Pennsylvania Scale Company in Leola PA in the early 1980’s. I learned that to work on what I wanted to work on I had to get my assigned duties done by noon or thereabouts. The most important lesson I had learned as a TV repairman, other than not to chew on the high voltage cable, was to use your eyes first. I would take a box of bad PCB’s that were essentially 6502 based computers that could count and weigh, and first go through inspecting them; usually the contents were reduced 50% right off by doing this. Then it was a race to identify and fix the remaining units and to keep my pace up I had to do my own desoldering.

Desoldering with IR System

Desoldering with IR System

It worked like this; you could set units aside with instructions and the production people would at some point go through changing components etc. for you or you could desolder yourself. I was pretty good at hand de-soldering 28 and 40 pin chips using a venerable Soldapulit manual solder sucker (as they were known). But to really cook I would wait for a moment when the production de-soldering machine was available. There was one simple rule for using the desoldering station: clean it when done! Failure to do so would result in your access to the station being suspended and then you might also incur the “wrath of production” which was not limited to your lunch bag being found frozen solid or your chair soaked in defluxing chemicals.

[Read more...]

Rolly Bot Puts a New Spin on Independent Wheel Control

rolly bot

All of [Darcy]‘s friends were making wheeled robots, so naturally, he had to make one too. His friends complicated theirs with h-bridges and casters for independent wheel maneuvering, but [Darcy] wanted something simpler. A couple of 9g servos later, the Rolly Bot was born.

Rolly Bot is self-balancing because of its low center of gravity. Should it hit a wall, the body will flip over, driving it back in the other direction. The BOM comes to a whopping $10, and that includes continuous rotation servos. It does not include the remote control capability he added later, or the cost of the CNC you would need to completely replicate this build. He even made a stand so he could test the wheels during programming.

[Darcy]‘s code is on his site along with some pictures of another version someone else built. Watch Rolly Bot roll around after the jump.

How would you make this build even simpler? Tell us in the comments.

[Read more...]

A Better, Cheaper Smartphone Thermal Imager

thermal

For the last few years, the prices of infrared thermal imaging devices have fallen through the floor, down from tens of thousands of dollars a decade ago, to just about a grand for a very high-resolution device. This dramatic drop in price was brought about by new sensors, and at the very low-end, there are quite a few very inexpensive low resolution thermal imaging devices.

The goal now, it seems, is to figure out some way to add these infrared devices to a smartphone or tablet. There have been similar projects and Kickstarters before, but [Marius]‘s entry for The Hackaday Prize is undercutting all of them, and doing it in a way that’s far, far too clever.

Previous ‘thermal imagers on a smartphone’ projects include the Mu Thermal Camera, a $300 Kickstarter reward that turned out to be vaporware. The IR-Blue is yet another Kickstarter we’ve seen, and something that’s actually shipping for about $200. [Marius] expects his thermal imager to cost just $99. He’s getting away with this pricing with a little bit of crazy electronics, and actually designing a minimum viable product.

Both the Mu Thermal Camera and the IR-Blue communicate with their smartphone host via Bluetooth. [Marius] felt radio modules were unnecessary and inspired by the HiJack system where low-power sensors are powered and read through a headphone jack, realized he could do better.

Always the innovator, [Marius] realized he could improve upon the HiJack power harvesting solution, and got everything working with a prototype. The actual hardware in the sensor is based on an engineering sample of the Omron D6T-1616L IR array module, a 16×16 array of IR pixels displaying thermal data on a portable device at 4 FPS.

It’s interesting, for sure, and half the price and quadruple the resolution of the IR-Blue. Even if [Marius] doesn’t win The Hackaday Prize, he’s at least got a winning Kickstarter on his hands. Video of the 8×8 pixel prototype below.


SpaceWrencherThe project featured in this post is an entry in The Hackaday Prize. Build something awesome and win a trip to space or hundreds of other prizes.


[Read more...]

Bare Bones Arduino IR Receiver

TV Remote

Old infrared remote controls can be a great way to interface with your projects. One of [AnalysIR's] latest blog posts goes over the simplest way to create an Arduino based IR receiver, making it easier than ever to put that old remote to good use.

Due to the popularity of their first IR receiver post, the silver bullet IR receiver, [AnalysIR] decided to write a quick post about using IR on the Arduino. The part list consists of one Arduino, two resistors, and one IR emitter. That’s right, an emitter. When an LED (IR or otherwise) is reverse biased it can act as a light sensor. The main difference when using this method is that the IR signal is not inverted as it would normally be when using a more common modulated IR receiver module. All of the Arduino code you need to get up and running is also provided. The main limitation when using this configuration, is that the remote control needs to be very close to the IR emitter in order for it to receive the signal.

What will you control with your old TV remote? It would be interesting to see this circuit hooked up so that a single IR emitter can act both as a transmitter and a receiver. Go ahead and give it a try, then let us know how it went!

Game Boy vs. Electronic Shelf Labels

SANYO DIGITAL CAMERAWhile they’re probably rare as hen’s teeth in the US, there have been a few major stores around the world that have started rolling out electronic shelf labels for every item in the store. These labels ensure every item on a shelf has the same price as what’s in the store’s computer, and they’re all controlled by an infrared transceiver hanging on the store’s ceiling. After studying one of these base stations, [furrtek] realized they’re wide open if you have the right equipment. The right equipment, it turns out, is a Game Boy Color.

The shelf labels in question are controlled by a base station with a decidedly non-standard carrier frequency and a proprietary protocol. IR driver chips found in phones are too slow to communicate with these labels, and old PDAs like Palm Pilots, Zauruses, and Pocket PCs only have an IrDA chip. There is one device that has an active development scene and an IR LED connected directly to a CPU pin, though, so [furrtek] started tinkering around with the hardware.

The Game Boy needed to be overclocked to get the right carrier frequency of 1.25 MHz. With a proof of concept already developed on a FPGA board, [furrtek] started coding for the Game Boy, developing an interface that allows him to change the ‘pages’ of these electronic labels, or display customized data on a particular label.

There’s also a much, much more facepalming implication of this build: these electronic labels’ firmware is able to be updated through IR. All [furrtek] needs is the development tools for the uC inside one of these labels.

There’s a great video [furrtek] put together going over this one. Check that out below.

[Read more...]

Follow

Get every new post delivered to your Inbox.

Join 96,467 other followers