I was splitting wood one day a few years back, getting next winter’s firewood ready on my hydraulic splitter. It normally handled my ash and oak with ease, but I had a particularly gnarly piece of birch queued up, and the splitter was struggling. The 20-ton cylinder slowed as the wedge jammed in the twisted grain, the engine started to bog down, then BANG! I jumped back as something gave way and the engine revved out of control; I figured a hydraulic hose gave out. Whatever it was, I was done for the day.
I later discovered that a coupler between the engine shaft and the hydraulic pump failed dramatically. It was an easy fix once I ordered the right part, and I’ve since learned to keep extras in stock. Couplings are useful things, and they’re the next up in our series on mechanisms.
One of the sticking points for us with our own Internet of Things is, ironically, the Internet part. We build hardware happily, but when it comes time to code up web frontends to drive it all, the thrill is gone and the project is only half-done.
Note that everything happens inside the ESP8266 here, from hosting the web page to interpreting and then blinking back out the IR LED codes to control the remote. This is a sophisticated “hello world”, the bare minimum to get you started. The interface could look slicker and the IR remote could increase its range with more current to the LED, but that would involve adding a transistor and some resistors, doubling the parts count.
For something like $10 in parts, though, this is a fun introduction to the ESP and BASIC. Other examples are simpler, but we think that this project has an awesome/effort ratio that’s hard to beat.
Need a simple fab process to go from a humble vector graphic to a final part — in a matter of minutes? The CO2 laser cutter might be the right choice. As these tools open themselves up to widespread use through hackerspaces, I decided to give Delrin some well-deserved time under the spotlight.
This guide is a brief collection of tips and techniques that I’ve either learned from others or discovered on my own over the last couple years working with laser-cut Delrin (a.k.a Acetal) for functional prototypes. I hope this guide serves you well as we keep exploring the limits of the material.
As a disclaimer, keep in mind that in no way are these techniques unique or limited to Delrin. Many are not only years old but also common practice in either engineering design or the local machine shop. This article simply highlights the techniques shown here that perform both repeatably and predictably with Delrin and a couple hand-tools, and I hope to share them with a growing audience of laser cutter enthusiasts.
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.
Today I am experimenting with a single chip Universal Active Filter, in this case I made a small PCB for the UAF-42 from Texas Instruments. I chose this part in particular as it facilitates setting the filter frequency by changing just a pair of resistors and the somewhat critical values that are contained on the chip have been laser trimmed for accuracy. This type of active filter includes Operational Amplifiers to supply gain and it supports various configurations including simultaneous operating modes such as Band Pass, Low Pass and High Pass make it “Universal”.
UAF421 Universal Active Filter
UAF421 Universal Active Filter using a dual ganged potentiometer.
Looking at the block diagram you can see where I have inserted a dual-ganged potentiometer to change both resistors simultaneously which should allow a straight forward adjustment for our purposes here.
Looking into the components of a simple RC filter which can easily implement a simple Low Pass or High Pass filter, we see that the math is fairly straight forward and swapping the components with each other is all that is needed to change the type of filter. Continue reading “Universal Active Filters: Part 1”→
Recently, our friends over at Adafruit released a new version of their popular TV-B-Gone kit. Built in cooperation with [Mitch Altman], the inventor of the TV-B-Gone, the new kit sports four high power IR LEDs, two wide beam and two narrow beam. The four LEDs give the new TV-B-Gone increased range, with a maximum distance of over 150ft. One of the most impressive features of the kit is the fact that the new TV-B-Gone is universal and can now work in Europe and Asia in addition to the US. Users are able to select which region they want to use during the build process by soldering a resistor into the board at their region’s corresponding spot as seen in the picture above. The new TV-B-Gone kit is now available in the Adafruit store for $19.95 plus shipping.
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