Author: Elliot Williams

1434 Articles

Ridiculously Complicated Home Automation Made Simple

February 12, 2015 by 33 Comments

[Eric T] wrote up his insanely-comprehensive home automation setup. What started out as a method to notify him when his dog barked grew into a whole-house, Arduino-powered sensor extravaganza. We’ve previously looked at two different steps from this mammoth article. One automated his dog, the other focused on the Wink hub to bridge with commercial hardware like smart lightbulbs. Now let’s look at the project as a whole.

The basic backbone of the project is actually quite straightforward. He made a radio gateway base station out of an Arduino, a RFM69 radio unit, and an Ethernet shield that connects to a Raspberry Pi to serve up a GUI interface. The open-source home automation project OpenHAB makes it all available through browser or smartphone.

Next, he made additional sensor nodes from Arduino and RMF69 radios. These sensor nodes can all be separate from each other, which has enabled [Eric] to expand his system incrementally over time.

Modules of particular interest are the Uber Sensor and the Washer-Dryer module. For the Uber Sensor, [Eric] basically threw every sensor he could at an Arduino; it sends noise levels, light levels, motion, temperature, humidity, and presence of smoke, flame, or flammable gas. Some of these conditions trigger e-mail alerts, while others are simply stored for future perusal.

On the simpler end of the spectrum, he uses a noise-level detector to detect the end of a laundry cycle and then trigger a notification. The clever bit is that the message is automatically cleared when an attached motion detector triggers, presumably because someone’s gone to the basement to empty the dryer. Very neat.

16All of this is basically made practical and affordable by the presence of simple Arduino libraries and cheap hardware modules purchasable over Ebay. If you’re at all interested in a DIY home automation project, this offering is worth a look for inspiration and a great overview.

How To Weigh An Eyelash

February 12, 2015 by 24 Comments

So you’re a boxer, and you’re weighing in just 80 micrograms too much for your usual weight class. How many eyelashes do you need to pluck out to get back in the ring? Or maybe you’re following the newest diet fad, “microcooking”, and a recipe calls for 750 micrograms of sugar, and you need to know how many grains that is. You need a microgram scale.

OK, we can’t really come up with a good reason to weigh an eyelash, except to say that you did. Anyway, not one but two separate YouTube videos show you how to build a microgram balance out of the mechanism in a panel meter. You know, the kind with the swinging pointer that they used to use before digital?

Panel meters are essentially an electromagnet on a spring in the field of a permanent magnet (a galvanometer). When no current flows through the electromagnet, the spring pulls the needle far left. As you push current through the electromagnet, it is attracted to the fixed permanent magnet, fighting the spring, and tugs the pointer over to the right. More current equals more pull.

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DIY SMD Twofer: Manual Pick-and-Place And The Beak

February 5, 2015 by 23 Comments

Populating a board with tiny SMT parts can be really tricky, and we’ll take all the help we can get. If you’re in the same boat, [vpapanik] has two devices you should check out.

First up is the manual pick-and-place machine. Wait, what? A manual pick-and-place? It’s essentially an un-driven 2-axis machine with a suction tip and USB inspection microscope on the stage. The picker apparatus is the “standard” needle-plus-aquarium-pump design, and the rails are made from angle aluminum and skateboard bearings.

Yeah, yeah, yeah. It’s not a robot. But sometimes the right jig or tool makes all the difference between a manual procedure being fiddly and being graceful. And we couldn’t help but laugh at the part in the video where he demonstrates the “machine” moving in a circular pattern.

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Logic Noise: Sweet, Sweet Oscillator Sounds

February 4, 2015 by 51 Comments

Welcome to part one of a series taking you down the rabbit hole of DIY electronic synthesizers based on (largely) CMOS logic chips. Instead of synths being commodity gear made by large corporate enterprises, we’ll be building with the cheapest available parts, using and misusing digital logic. In short, don’t expect pre-packaged smooth tones, because we’ll be making creative noise machines.

If you’re the chiptunes type, you’ll probably find something you like here. If you’re the circuit bender or electro-noise-punk type, this is gonna be right up your alley. If you just like to see CMOS chips wriggle and squirm in unintended ways, feel free to look over my shoulder. If you’re the type who insists that a screwdriver can’t be used to pry open a paint can, then maybe you’d better move along. There’s a thin line between the glitch as bug and the glitch as interesting discovery, and we’ll be dancing all over it.

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Semi-Auto PCB Drill Press Makes Drilling Semi-Painless

February 4, 2015 by 50 Comments

DIY PCBs are the fastest and cheapest way to iteratively prototype circuits, and there’s a lot of great tricks to get the copper layer just the way you want it. But if you’re using through-hole parts, you eventually have to suffer the tedium of drilling a potentially large number of precisely aligned holes. Until now. [Acidbourbon] has built up a very nice semi-automatic PCB drill machine.

Semi-automatic? The CNC machine (with PC-side software) parses the drill file that most PCB design software spits out, and moves an X-Y table under your drill press to just the right spots. The user manually drills the hole and hits enter, and the table scoots off to the next drilling location. All of this is tied together with a simple calibration procedure that figures out where you’ve got the board using two reference drill locations; you initially jog the platform to two reference drill holes, and you’re set.

The CNC conversion of a relatively cheap X-Y table is nicely documented, and the on-board touchscreen and USB interface seem to make driving the machine around painless. Or at least a lot less painful than aligning up and drilling all the holes the old-fashioned way. Everything is open-source, so head on over and check it out.  (And while you’re there, don’t miss [Acidbourbon]’s tips and tricks for making PCBs using the toner transfer method.)

Seeing this machine in action, we can’t wait for the fully automatic version.

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3D Printed Surfboard

January 26, 2015 by 25 Comments

You whippersnappers these days with your 3D printers! Back in our day, we had to labor over a blank for hours, getting all sweaty and covered in foam dust. And it still wouldn’t come out symmetric. Shaping a surfboard used to be an art, and now you’re just downloading software and slinging STLs.

Joking aside, [Jody] made an incredible surfboard (yes, actual human-sized surfboard) out of just over 1 kilometer of ABS filament, clocking 164 hours of printing time along the way. That’s a serious stress test, and of course, his 3D printer broke down along the way. Then all the segments had to be glued together.

But the printing was the easy part; there’s also fiberglassing and sanding. And even though he made multiple mock-ups, nothing ever goes the same on opening night as it did in the dress rehearsal. But [Jody] persevered and wrote up his trials and tribulations, and you should give it a look if you’re thinking of doing anything large or in combination with fiberglass.

Even the fins are 3D printed and the results look amazing! We can’t wait for the ride report.

Shaka.

When Adding Noise Helps

January 25, 2015 by 20 Comments

It’s a counterintuitive result that you might need to add noise to an input signal to get the full benefits from oversampling in analog to digital conversion. [Paul Allen] steps us through a simple demonstration (dead link, try Internet Archive) of why this works on his blog. If you’re curious about oversampling, it’s a good read.

Oversampling helps to reduce quantization noise, which is the sampling equivalent of rounding error. In [Paul’s] one-bit ADC example, the two available output values are zero volts and one volt. Any analog signal between these two values is rounded off to either zero or one, and the resulting difference is the quantization error.

In oversampling, instead of taking the bare minimum number of samples you need you take extra samples and average them together. But as [Paul] demonstrates, this only works if you’ve got enough noise in the system already. If you don’t, you can actually make your output more accurate by adding noise on the input. That’s the counterintuitive bit.

We like the way he’s reduced the example to the absolute minimum. Instead of demonstrating how 16x oversampling can add two bits of resolution to your 10-bit ADC, it’s a lot clearer with the one-bit example.

[Paul’s] demo is great because it makes a strange idea obvious. But it got us just far enough to ask ourselves how much noise is required in the system for oversampling to help in reducing quantization noise. And just how much oversampling is necessary to improve the result by a given number of bits? (The answers are: at least one bit’s worth of noise and 22B, respectively, but we’d love to see this covered intuitively.) We’re waiting for the next installment, or maybe you can try your luck in the comment section.