Using an Arduino to measure inductance

Measuring an inductor is not something that most multi-meters can do. You usually need a high precision resistor (1% or better) in series with the inductor, a function generator to put a signal through the circuit, and an oscilloscope to measure the result. But what can you do if you don’t have these tools on hand? [Andrew Moser] has a method that lets you pull it off with an Arduino and an LM339 quad comparator.

The circuit works by feeding a signal in from the Arduino. This waveform is affected by the LC circuit, filtered by the comparator chip, then read back out the other side by the Arduino. That resulting signal is a square wave, which is an easy target for the Arduino to measure. That timing measured from the square wave can then be used to calculate the inductor’s value.

This is quite handy if you’re winding your own inductors. Now you can precisely tune that Joule Thief you’ve been working on.

[via Dangerous Prototypes and Adafruit]

Creating music from GPU noise

Yep, that’s a picture of a Laptop rocking out on an electric guitar. In what can only be described as a truly bizarre hack [CNLohr] discovered that the RF noise from the computer can be used to play music through the guitar’s pickup.

Check out the clip after the break to hear an annoying, but very discernible rendition of Jingle Bells. Once [CNLohr] stumbled onto the fact that changes in what the graphic processing unit is doing was affecting the pitch detected by the pickup he started writing some code. Now he’s got a program that automatically calculates the size of the window, and produces a white square on a black background to dial in the GPU at the right frequencies.

He mentions in the notes accompanying his video that he had to turn off Vsync to get this to work right. We don’t understand why but we’d love to hear what you think in the comments.

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