Author: Al Williams

4505 Articles

High Performance Crystal Radio

September 16, 2016 by 16 Comments

When you think of a crystal radio, you probably think of something simple maybe built out of household scraps. Not if you are [Chris Wendling]. He recently posted a video (see below) of his high-performance crystal set. He doesn’t take any shortcuts: he has several hundred feet of antenna wire, and uses a cold-water pipe ground system. With no amplifier, a strong signal input is crucial.

The radio has four subsystems: an antenna tuner, a bandpass filter, a detector, and a powered audio output system. He also has a truly enormous system of speakers on the ceiling–this isn’t the crystal radio you made in the boy scouts.

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Yet Another Inductance Measuring Scheme

September 15, 2016 by 13 Comments

How do you measure the value of an unknown inductor? If you have an LCR bridge or meter, you are probably going to use that. If not, there are many different techniques you can use. All of them rely on the same thing my Algebra teacher Mr. Harder used to say back in the 1970’s: you have to use what you know to get what you don’t know.

[Ronald Dekker] must think the same way. He took a 50-ohm signal generator and a scope. He puts the signal output to about 20kHz and adjusts for 1V peak-to-peak on the scope. Then he puts the unknown inductor across the signal and adjusts the frequency (and only the frequency) for an output of 1/2 volt peak-to-peak.

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Custom Gaming Keypad Developed With PSoC And Fusion 360

September 15, 2016 by 8 Comments

There was a time when building something yourself probably meant it didn’t look very much like a commercial product. That’s not always a bad thing. We’ve seen many custom builds that are nearly works of art. We’ve also seen plenty of builds that are–ahem–let’s say were “hacker chic”.

[AlexanderBrevig] decided to take on a project using a PSoC development board he picked up. In particular, he wanted to build a custom game keypad. He prototyped a number of switches with the board and got the firmware working so that the device looks like a USB HID keyboard.

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Robotic Arm From Cardboard

September 14, 2016 by 7 Comments

Google showed the world that you could make a virtual reality headset from cardboard. We figure that might have been [Uladz] inspiration for creating a robotic arm also made out of cardboard. He says you can reproduce his design in about two hours.

You’ll need an Arduino and four hobby servo motors. The cardboard doesn’t weigh much, so you could probably use fairly small motors. In addition to the cardboard, there’s a piece of hardboard for the base and a few metal clips. You can control it all from the Arduino program or add an IR receiver if you want to run it by remote control. There’s a video of the arm–called CARDBIRD–in action, below.

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Optimizing The Spread: More Spreadsheet Circuit Design Tricks

September 14, 2016 by 6 Comments

Last time I showed you how to set up a reasonably complex design in a spreadsheet: a common emitter bipolar transistor amplifier. Having the design in a spreadsheet makes it easy to do “what if” scenarios and see the effects on the design almost immediately.

Another advantage that spreadsheets offer is a way to “solve” or optimize equations. That can be very useful once you have your model. For Excel, you need to install the Solver add-in (go to the Excel Options dialog, select Manage Add-Ins, and select the Solver Add-In). You might also enjoy OpenSolver. You can even get that for Google Sheets (although it currently lacks a non-linear solver which makes it less useful for what we need).

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3D Printing School Of Knocks

September 10, 2016 by 15 Comments

Unless you are under age 20, there are probably things you know now that you wish you knew growing up. Even on hacker projects, it isn’t unusual to do better on your second whatchamacallit than on your first one. After all, you learn something each time and apply it to subsequent builds.

[James Lewis] (sometimes known as the [Bald Engineer]) has spent a couple of years with a 3D printer. He says that as of March this year, he had used the machine for about 75 hours. Since then his usage went up to 300 hours because he’s finally learned his lessons about how to get good prints.

If you are experienced, you might not be surprised at the first tip: level the bed. Don’t let that fool you, though. [James] has some good tips on advanced bed materials and print filament, too.

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Raspberry Pi Plays All That Jazz

September 10, 2016 by 14 Comments

[James Bellafaire] wanted a good looking old radio with a modern sound. Granted, you could hollow the case out and replace it with an iPod. Or you could convert the thing to an Internet radio. But where’s the fun in that?

[James] took a different approach. Part woodworking project, part Raspberry Pi project, and part microcontroller project, he wound up with a hard drive-based music player in a 1930’s case with knobs that control the playback.

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