Tag Archives: Hacks

Brute force computation for cheap log digital potentiometer

via Dangerous Prototypes

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Michael from Acidbourbon writes:

This article covers the attempt to build a digital logarithmic potentiometer out of two linear potentiometers. The benefits of this concept

  • Linear digital potentiometers can be easily procured and don’t cost much
  • There are IC packages with two or four modules inside anyway
  • The resulting logarithmic potentiometer is very flexible in terms of number of steps and steepness of the attenuation function

Full details at Acidbourbon homepage.

Turn an old payphone into a boombox for ’90s hits

via Arduino Blog

If you grew up in the ’90s and would love to play some of your favorite hit songs through something a bit more nostalgic than your smartphone, perhaps you can do what “digital alchemist” Fuzzy Wobble has done and transform an old-school payphone into a fully-functional boombox.

Fuzzy Wobble was able to get his hands on an inexpensive payphone and hacked it using an Arduino Mega, an Adafruit MP3 Maker Shield, a 20W amplifier, a 20W speaker, and some other components. The unique boombox is also equipped with a rangefinder that detects whenever someone walks by, triggering the phone to ring and enticing someone to answer the call.

The phone is programmed with a recorded menu along with instructions on how to select one of several pre-loaded songs. Hitting the star key sends the device into broadcast mode.

What’s neat is that there’s a tiny booklet filled with images of ’90s tunes, from Coolio to Sugar Ray to Semisonic, each with a four-digit number on the back. Simply punch in the code and the payphone begins to play music.

Pretty awesome, right? You can build one yourself by following Fuzzy Wobble’s step-by-step Instructable here, and check out his demo video below.

Automatic volume tracking for a TV

via Dangerous Prototypes

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An automatic volume tracker by KA7OEI:

It occurred to me that I did have a reference on which I could base an outboard volume control: The internal speakers of the TV. I surmised that I could “listen” to the audio level coming out of the speakers and based on that, adjust the volume of an outboard amplifier. I figured that this could work if I could place a sense microphone very close to the speaker and in this way the sound level at the microphone would be very high as compared to the room volume of the external loudspeakers and I could make it so that not only would the TV’s internal speakers still be quite low for a fairly high volume from the outboard speakers, but also prevent sound from the outboard speakers from being picked up by the microphone and cause the volume to increase even more in a feedback loop.

To test this theory I hacked together a bit of code that did nothing but measure the audio level from two sources:  A microphone and the audio line output and then dump those levels, in dB, to the serial port where I could see what was going on .  It seemed to look pretty good as the two audio sources seemed to track fairly well.

RC2014/LL and RC2016/10

via Dangerous Prototypes

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Scott Lawrence has written an article detailing his Z80 homebuilt computer, the RC2014:

The RetroChallenge is upon us again!
This time around, I plan on working on my Z80 homebuilt computer, the RC2014. (Website for RC2014, Order a RC2014) For a few months now, I’ve had my RC-2014 computer built, and modified to be an RC2014/LL computer. What this means is, is that I have some modified modules using no additional external hardware.
The above picture shows my RC2014/LL system with its extra RAM module, and the C0 Serial expansion board to the left, with the SD card interface board (SSDD1) on it.

Project info at Scott Lawrence’ blog.

DIY USB power bank from laptop battery

via Dangerous Prototypes

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DIY USB power bank made from an old laptop battery from DoItYourselfGadgets:

A situation many can relate to: an empty smartphone battery and no outlet around! That’s exactly why I recycled an old laptop battery into an USB power bank.
This article will show you the basic powerbank circuit consisting of Lithium cell charging circuit, boost converter and toggle switch as well as my improved version with self activating boost converter and LED status indicator and homemade housing.

More details at DoItYourselfGadgets project page.

Check out the video after the break.