It’s time for a lecture. I’ve been spending a lot of time creating a DIY dlectrocardiogram and it produces fairly noisy signals. I’ve spent some time and effort researching the best ways to clean-up these signals, and the results are incredibly useful! Therefore, I’ve decided to lightly document these results in a blog entry.
Here’s an example of my magic! I take a noisy recording and turn it into a beautiful trace. See the example figure with the blue traces. How is this possible? Well I’ll explain it for you. Mostly, it boils down to eliminating excess high-frequency sine waves which are in the original recording due to electromagnetic noise. A major source of noise can be from the alternating current passing through wires traveling through the walls of your house or building. My original ECG circuit was highly susceptible to this kind of interference, but my improved ECG circuit eliminates most of this noise. However, noise is still in the trace (see the figure to the left), and it needed to be removed.
Signal Filtering with Python - [Link]
There are many times where you would like to “stabilize” an input signal so that you don’t see the input value “jumping” so much. This is specially true on the MilliVolt Signal range, where nearby noise present can disturb the original signal. In this case, you always have the option of buying some kind of signal conditioner, which handles the filtering function of the raw signal. However, there are many times where the noise problem presents itself after the system is built, in which case a simple software solution is preferable to mitigate the problem.
Simple Software Filter - [Link]
Festivize your bench this holiday season with an oscilloscope Christmas tree – [via]
When I was a little kid, my dad worked at Bell Labs. Every year around Christmas, we’d go visit him at work. One memory which has always stuck with me from my holiday visits was seeing a Christmas tree on an oscilloscope. I was pretty amazed by it. Engineers are a funny bunch — they tend to celebrate holidays in the most uniquely nerdy and wonderful ways, just like kids. When I recently acquired a new ‘scope and wanted to familiarize myself with it, I knew exactly what my test circuit was going to be.
In honor of the nameless BTL engineer whose scope scribbling captivated me as a child, here we are. Maybe the same thing will happen for some other kid. There are a lot of holiday parties coming up. You could put this on one of your scopes at work or at your hackerspace, and some other kid will see it, and it’ll fire their imagination too. It looks pretty neat at any rate, and it’s downright fascinating after a few fortified egg nogs.
Oscilloscope Christmas Tree - [Link]
Random Stories from China @ bunnie’s blog – [via]
Yep, that’s right, the book of iPhone schematics. I snapped that baby up for $4. My feeling is that these schematics probably come from leaks of original Apple sources, because many of the annotations couldn’t be divined from a clean-room reverse engineering job. For example, the above schematics annotate that the AP_UART connection on the dock has a dual-footprint option for a possible drop-in DisplayPort upgrade. Anyways, these schematics are useful as a sourcing guide for cheap components. Any part found in this book has been made in millions-per-week quantities, which is a handy fact to keep in mind when bargain hunting for stable supplies of cheap components.
iPhone schematics and more… - [Link]
For a while now, my friends and I have been brewing beer at my house. I was inspired by an old Sparkfun tutorial about a bubble logger for Nate’s terrible wine. I figured that while logging bubbles is interesting and all, wouldn’t it be more useful to have real-time information on the fermentation process? I basically copied the optical gate method of counting bubbles, added a sensitive pressure sensor, and an AVR development board (Yes, Arwen, that’s your old TekBots board! ).
Homebrew bubble counter - [Link]
Very often when designing some stuff I need a square wave signal generator with variable pulse width and frequency to control power MOSFETS.
You can use such a tool when designing DC-DC converter or switch-mode power supply, you can use it to emulate PWM from microcontroller when developing some new embedded design, or maybe you want to design your own wireless charger… This is only some of the things you can use it for.
PWM Generator Project - [Link]
Apparently I have a thing for testing. I rather love to run experiments, even when there’s no immediate need for the results. I guess I just enjoy trying stuff, and hey, maybe even learning a thing or two.
So last weekend I was doing a bit of tinkering and got to wondering about the performance of different heatsinks. Now just intuitively, I know that larger heat sinks tend to dissipate more heat than smaller ones – particularly if they have larger surface areas. But just how much better is a tall, finned heatsink than a small, clip-on device? This is what I wanted to find out. So I gathered up five sinks of varying sizes and started to design my test.
Compares the performance of several different heatsinks - [Link]
Camelpunch: The Brushduino. Steve writes… [via]
Ever have an idea that people tell you “you should TOTALLY patent that!” Well, I did, and they did, and I thought about it… but instead I decided to open source the whole thing. It seemed like kind of an obvious idea to me and going after a patent made me feel kind of greedy. Besides, all of my prototyping was done with open source tools!
Anyways, I hope someone can improve upon this. I think it’s a useful thing.
My daughters don’t brush their teeth long enough, if left to their own devices. When my wife or I brush their teeth, we do a nice thorough job that takes a little while but when the girls do it themselves, they tend to cut it short. Timing them doesn’t help, as they just stand there and chit-chat until the timer goes off. It’s not that they don’t brush their teeth LONG enough, it’s that they don’t brush their teeth WELL enough.
It occurred to me that if could make something that monitored how WELL they brush their teeth—and maybe even guided them through the process a little—then they’d eventually establish better habits for the future. I started thinking about what I could build that would help them and settled on the notion that an accelerometer was the perfect sort of thing to keep tabs on what constitutes a brush “stroke” while they’re in there brushing their teeth. All I’d need to do is come up with a little hardware and software to make it happen.
The Brushduino – Helps kids brush their teeth better… - [Link]
Conductive Silver Ink from a Ballpoint Pen via BB… [via]
Materials researchers at the University of Illinois, Urbana-Champaign have developed a highly conductive silver ink. In this video, Analisa Russo, a graduate student in the research group of Professor Jennifer Lewis shows exactly how to make this amazing ink, which could be used for a wide variety of hobby projects and in advanced electronics hardware.
Conductive Silver Ink from a Ballpoint Pen - [Link]
BBC News – Steve Wozniak’s tribute. – [via]
The co-founder of Apple says he will remember Steve Jobs for his “very quick mind” and “knowing what made sense in a product”. Steve Wozniak, who met Mr Jobs at school and was in a computer club with him before starting the company, said: “How many things do you own in the world… that are ‘I just have to have this… I actually enjoy doing my work on this product’? That’s what Apple brought to so many people.”
“We went into the garage when we were two young people with no money. You have to work out of your home. We had jobs on the side. We had nobody that could loan us money. We had no business experience. We were like a million young people who are so excited about the future they may have some day, in business, making something just out of their ideas. That’s what we were.” — Steve Wozniak
Steve Wozniak’s tribute - [Link]