An easy way to conceptualize active filters is thinking about audio speakers. A speaker crossover has a low-pass, high-pass and band-pass effect breaking a signal into three components based upon frequency. In the previous part of this series I took that idea and applied it to a Universal Active Filter built with a single chip opamp based chip known as the UAF-42. By the way, it’s pretty much an older expensive chip, just one I picked out for demonstration.
Using a dual-ganged potentiometer, I was able to adjust the point at which frequencies are allowed to pass or be rejected. We could display this behavior by sweeping the circuit with my sweep frequency function generator which rapidly changes the frequency from low to high while we watch what can get through the filter.
In this installment I’ll test the theory that filtering out the harmonics which make up a square wave results in a predictable degradation of the waveform until at last it is a sine wave. This sine wave occurs at the fundamental frequency of the original square wave. Here’s the video but stick with me after the break to walk through each concept covered.
Continue reading “Universal Active Filters: Part 2”
Here’s your chance to grab a tangible piece of Hackaday. This morning we are starting pre-orders for the Hackaday Omnibus 2014. This is our first-ever print edition. It collects some of the best original content published on Hackaday in 2014.
We’re proud of what the Hackaday crew accomplished last year. From stories of old and new to articles that encouraged you to stretch your hacking universe, we are thrilled with the original content articles we saw published last year. To go along with this top-tier content, we added amazing art and illustrations from [Joe Kim]. The product is something that demands commemoration in print and thus the Omnibus was born.
This full-color, 80 page, perfect binding volume is just what your coffee table has been crying out for. Of course it will look spectacular covered in solder and clipped resistor leads on the bench. And if your company is serious about hardware you need to send that message with a copy of the Omnibus in the reception area (or comically in the commode).
We are pricing the Hackaday Omnibus 2014 at $15 but we will sweeten the deal if you get in on the preorder. Use this coupon code to get $5 off: OMNIBUS2014. The coupon will work for the first 500 copies pre-ordered with an estimated shipping date of 2/9/15.
It’s time to announce the winners of the Trinket Everyday Carry Contest! We’ve had a great 5 weeks watching the projects come together. A team of Hackaday staffers spent their weekend watching videos and selecting their top entries based on the contest rules. We had a really hard time picking the top three – the competition was tight, and there were quite a few awesome projects.
Without further ado, here are the winners!
First Prize: 1337 3310 tool. [Mastro Gippo] really knocked this one out of the park. He built a swiss army knife of a tool out of the iconic Nokia 3310 candybar phone. 1337 3310 tool is a graphing voltage and current meter, an ohmmeter, a continuity tester that plays the original Nokia ringtone, and a gaming machine which can play Tetris. [Mastro Gippo] is 99% there with TV-B-Gone functionality as well. Amazingly, [Mastro Gippo] kept the Nokia look and feel in his user interface. He spent quite a bit of time grabbing data and bitmaps from the 3310’s original ROM. [Mastro Gippo] is getting a Rigol DS1054Z scope to help iron out the bugs in his future projects!
Second Prize: Pavapro – portable AVR programmer. [Jaromir] built an incredible pocket-sized microcontroller programming tool. Pavapro can read and edit text files, handle serial I/O at 9600 baud, and burn AVR microcontrollers. If that’s not enough, it can actually assemble AVR binaries from source. That’s right, [Jaromir] managed to fit an entire assembler on the Pro Trinket’s ATmega328 processor. Pavapro’s 16 button keypad won’t allow for much in the way of touch typing, but it does get the job done with T9 style text entry. The device is also extensible, we’re hoping [Jaromir] adds a few other architectures! PIC and MSP430 modes would be awesome! [Jaromir] will be receiving a Fluke 179 multimeter with a 6 piece industrial electronics tip kit! We’re sure he’ll put it to good use.
Third Prize: Robotic 3rd Hand. Let’s face it. We can’t all be Tony Stark. But [Tim] gets us a little bit closer with his awesome wearable entry. Need a tool? Just press the button, and Robotic 3rd Hand will give you a … hand. [Tim’s] creation utilizes the Pro Trinket to drive a servo which moves an incredibly well designed and 3D printed mechanism that lifts a screwdriver off the wearer’s wrist and places it into their hand. [Tim] originally was going to go with Electromyography (EMG) sensors to drive the hand, however he switched to a simple button when they proved problematic. We absolutely think this was the right decision for the contest – it’s always better to have a simpler but working project rather than a complex yet unreliable one. That said, we’d love to see him circle back and give EMG another try! [Tim’s] next project will be soldered up with the help of a Hakko FX888D with a tip kit. If things get a bit wobbly, he can use his new Panavise 324 Electronic Work center to keep everything steady.
If you didn’t make the top three in this contest, don’t give up! We’re going to be having quite a few contests this year. The top 50 entrants will receive custom Hackaday EDC Contest T-shirts. Check out the full list of 50 on Hackday.io!
We’ve got just under 2 days left in the Trinket Everyday Carry Contest. With 79 entries, and t-shirts going to the top 50 entrants, you’ve got pretty darn good odds of getting a shirt out of all of this! The design is great too, [Joe Kim] really did a great job with it!
The idea is simple: Build small, pocketable projects which are useful everyday.
We explained everything in our announcement post, and the full rules are available on the contest page. But just as a reminder, the main requirements are
- The project Must use a Pro Trinket, or a board based on the open source Pro Trinket design.
- The project must have at least 3 project logs
- The project must have at least one video
- The Hackaday.io project must include enough documentation to allow an average hobbyist to replicate the project
There are already some awesome entries vying for the top prize, but who knows – someone may come out of nowhere and walk away with a sweet Rigol ds1054z oscilloscope!
The contest deadline is January 3rd, at 12:00 am PDT. The clock is ticking, so stop waiting, and go build something awesome! Good luck to everyone who enters!
Now that we’ve recovered from our Munich party and the awarding of The Hackaday Prize, we’re ready to announce our latest contest. We’ve been having a lot of fun with our Trinket Pro boards, both the 10th anniversary edition and the new Hackaday.io branded models. While we were soldering, compiling, and downloading, a contest idea took root. Trinket Pro really excels when used in small projects, the kind which would fit in a pocket. To that end we’re holding the Trinket Everyday Carry Contest, a showcase for small, pocketable projects which are useful everyday. ‘Useful everyday’ is a bit of a broad term, and we intended it that way. Tools are useful of course , but so are jewelry pieces. It’s all in the eye of the builder and users. We’re sure our readers will take this and run with it, as they have with our previous contests.
There are some great prizes in store for the entrants, including a brand new Rigol DS1054Z oscilloscope! The top 50 entrants will get custom Trinket Everyday Carry Contest T-shirts. Check out the contest page for a full list.
We know you all love to procrastinate with your entries, so we’re going to be offering a few perks to those who enter early and update often. Each week, we’ll throw all the entrants who have published at least one project log full of details into a drawing for a special prize from The Hackaday Store. To be considered you must officially submit your project which is accomplished through a drop-down list on the left side of your project page.
Remember, the contest isn’t just about winning a scope, a meter, or any of the other prizes. It’s about creating new Open Hardware designs that nearly anyone can build. So grab those soldering irons, load up those copies of the Arduino IDE, AVR-GCC, or WinAVR, and get hacking!
You can view the all of the contest entries in this list.
The Hackaday Prize is here! We know you can’t all be here with us in Munich so we’ve set up a live stream link for everyone to follow along at home. If you tune in now, you can catch some of the talks at our open hardware event!
Check it out: Hack-O-Vision
The awarding of The Hackaday Prize is nearly upon us! With just over a day left to go, Launch Judge Elecia White has decided to spill the beans and write a blog post about which of the five finalists she thinks should win. We don’t want to spoil the surprise… but what the heck, she wants them ALL to win.
ChipWhisperer because it brings high-end hardware security tools to the masses.
SatNOGS because it brings space to your back yard,
PortableSDR because of its great waterfall display,
ramanPi because come on, it’s a freaking spectrometer!
Open Source Science Tricorder because it uses sensors to help us see the science in the world around us.
Elecia knows how much time, effort, and passion went into these projects, and how each one embodies the open and connected spirit of The Hackaday Prize. Only one day remains before the big event in Munich, and the announcement of the winner.