Halloween Hacks: The Headless Dogman

November 1, 2011 by Mike Nathan 4 Comments

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Typically, when people hear that you’ve made a Halloween costume for your dog, the statement is met with the eye rolling and polite lies about how cute the outfit is. There are few exceptions to this rule, and [Dino’s] latest creation is one of them. For this week’s entry in his Hack a Week series, he created a “Headless Horseman” costume for his dog [Sophie].

The costume borrows parts from one of his previous hacks, the Hexababy. Reclaiming the dismembered head from the disturbing crawler, [Dino] reattaches it to the doll’s body, just not in the traditional manner. He screws the baby’s head to the arm of the doll after fashioning its outfit from some scrap cloth. The doll’s head retains it’s beady red LED eyes from the previous project, but [Dino] added a tilt switch to the setup so that they light up sporadically as the dog runs about.

Be sure to check out the video below to see the final result of [Dino’s] work. The doll looks great, though it seems that its saddle needs some reinforcement to handle [Sophie’s] bountiful energy stores.

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[Dino] Builds A Simple Non-contact Voltage Detector

September 20, 2011 by Mike Nathan 30 Comments

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[Dino] is back with another installment of his Hack a Week series, and in this episode he is taking on what he promises will be the last transistor-based project – at least for a little while.

In the video embedded below, he shows off a homemade voltage detector circuit that he constructed using a trio of BC547 NPN transistors. The circuit is pretty simple though very useful all the same. At one end, the device has a small copper strip, which is connected to the base of the first transistor. The emitter of that transistor is daisy chained to the base of the second transistor and so on, until reaching the indicator LED.

As noted by one of [Dino’s] viewers, the circuit functions as follows:

“The front end copper strip forms one side of a capacitor, and then when you bring it near a voltage potential a super tiny current flows between air dielectric of the “cap”. This is mega amplified with the high gain BC547′s and viola, the LED lights up.”

Since the small bit of current is amplified many times over, the LED lights up even when very small voltages are present. While we might not necessarily trust our lives to [Dino’s] voltage detector, we’re sure it would come in handy now and again.

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Simple Transistor Tester Makes Sorting Easy

September 2, 2011 by Mike Nathan 26 Comments

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Hacker [Dino Segovis] is back with yet another installment of his Hack a Week series, and it’s looking like he isn’t too worse for wear after hunkering down to face hurricane Irene.

This week, it seems that [Dino] is having some problems separating his PNP transistors from his NPNs. After Albert Einstein proves to be less than useful when it comes to sorting electronic components, [Dino] decided to build a simple transistor tester to help him tell his PNPs and NPNs apart without having to resort to looking up product data sheets.

The tester itself is relatively simple to build. As you can see in the video below, it consists of a power supply, an LED, a few resistors, a pair of known transistors, and not much else. When everything is hooked together, the NPN/PNP pair causes the LED to light up, but the circuit is broken whenever one of the transistors is removed. Inserting a new transistor into the empty spot on the breadboard immediately lets you know which sort of transistor you have inserted.

Sure you can tell transistors apart with a multimeter, but if you have a whole drawer full of loose components, this is a far more efficient option.

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[Dino] Tells Us About Transistor-based On/off Switches

August 22, 2011 by Mike Nathan 12 Comments

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You know them, you love them, you take them for granted – they are single push button on/off switches. As [Dino] explains in the most recent episode of his Hack a Week series, they are typically implemented in the form of IC logic switches nowadays, but it wasn’t always that way. When they first came on to the scene in the 70’s, the single button soft switches were built using a set of transistors and a capacitor to get the job done, so [Dino] decided to research push on/push off transistor switches a bit and build his own.

After reading through a short tutorial, he was ready to go. As he explains in the video, the operation of the switch is fairly simple, though he did run into some odd issues when he prototyped the switch on a piece of breadboard. He’s looking for someone to explain why the unstable circuit suddenly performs better with the addition of a small capacitor between the battery’s positive lead and the circuit’s output, so if you have some insight, be sure to speak up in the comments.

In the meantime, check out [Dino’s] exploration of push on/push off switches below.

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Quick And Easy Audio Preamp

August 6, 2011 by Mike Nathan 16 Comments

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The most recent installment of [Dino Segovis’] Hack a Week covers the construction of a simple NPN transistor audio preamp. Some time ago, he built a small audio amplifier using an LM386 which worked well, but didn’t quite get his music as loud as he would like it. He decided to build a preamp to complement his amplifier, and demonstrates how you too can build one with just a small handful of components.

As the name probably suggests, the cornerstone of this amplifier is an NPN transistor. He explains that a forward bias is applied to the base-emitter junction, which results in the transistor operating halfway between its cut-off and saturation regions. Both halves of the input audio signal are superimposed on this bias voltage, resulting in a decent amount of gain across both channels from a relatively small package.

The preamp isn’t going to win any awards among audiophiles, but it is definitely a great beginner project. Its a novel way of demonstrating how transistors work, while producing a useful takeaway piece of audio equipment at the same time.

Continue reading to see a video showing just how big an effect [Dino’s] NPN preamp had on his music.

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Propeller-based Robot With Basic Object Avoidance

July 6, 2011 by Mike Nathan 6 Comments

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The Parallax Propeller is a pretty powerful MCU as [Dino] recently discovered in his latest Hack a Week installment. He wanted to build a simple robotics platform that he could use for testing out various sensors, and he figured he might as well learn about a different type of micro controller in the process.

He pieced together his robot using a pair of old Roomba motors he had sitting around, mounting them on a standard RadioShack project box. A Propeller MSR1 control board runs the show, and a Propeller PING sensor is used to get an idea of what the robot’s surroundings look like. He is an admitted newbie when it comes to using Propeller micro controllers, but [Dino] was able to give his robot some rudimentary object avoidance abilities fairly easily. A few small bugs aside, he had the robot up and running in short order, a testament to how easy it is to work with the Propeller platform.

Stick around to see a brief video covering the robot’s construction we have embedded below.

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[Dino] Celebrates The 131st Anniversary Of The Photophone

June 3, 2011 by Mike Nathan 24 Comments

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[Dino Segovis] wrote in to share yet another installment of his Hack a Week series, though this one is quite timely.

It was 131 years ago today that [Alexander Graham Bell] unveiled the Photophone to the world. A precursor to fiber optic technology, [Bell’s] incredibly important invention can be easily replicated in your garage, as [Dino] shows us.

The original Photophone was constructed using a megaphone and crystalline selenium cells at the focal point of the receiver, however this version can be made with easy to obtain parts. [Dino] rigged his laptop up to a speaker on which he mounted a mirror, before setting it out in the sun. The vibrations of the mirror modulate the sunlight, reflecting it onto a solar cell positioned at the end of a long, black PVC tube. The solar cell’s leads are fed into an amplifier followed by a speaker, which broadcasts the audio.

The demonstration goes off without a hitch, and while some might be underwhelmed by the technolgy, imagine how incredible it would have looked 131 years ago!