Zenotron: the Looks of a Kaypro II with the Soul of a Nebulophone

This beautiful instrument of musical delight is called the Zenotron, and it was built by [Mike Walters] for his friend [Zeno] in exchange for some keyboards. The Zenotron is the latest musical hack in a long line of awesome from the same guy who built the Melloman, its successor, the Mellowman II, and Drumssette, a programmable sequencer.

The sweet sounds of those babies all come from tape loops, but the Zenotron is voiced with a modified [Bleep Labs] Nebulophone synthesizer. Instead of the Nebulophone’s pots controlling the waveform and arpeggio, he’s wired up a 2-axis joystick. He left the LFO pot wired as-is. When it’s turned all the way down, he’s noticed that the joystick takes over control of the filter. [Mike] fed the audio through a 4017 decade counter and each of the steps lights up an array of four to five of the randomly-wired 88 LEDs.

[Mike] made the case from the top half of a small filmstrip viewer and an old modem, which is way better than the Cool Whip container housing we made for our Nebulophone. He re-purposed a toy keyboard and made a contact board for it with small tactile switches. This results in nice clicky feedback like you get from mouse buttons.

Of course there’s a demo video. You know the drill.

 

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One wire reads the keypad from the APRS radio mic

[Shane Burrell] decided to spend some time learning how the keypad on the his Kenwood TM-710A APRS radio mic works. It uses a different technique than you might think. Normally a grid of buttons is scanned as a matrix to detect keypresses, but this hardware actually counts pulses on a serial wire to take each reading.

The stock radio sends a steady digital pulse to the handset and with each pulse the mic pulls the line low. It then uses a 4017 decade counter to see what comes back. If the edge count matches it means nothing is pressed, but a change in the number of pulses returning to the base unit can be used to extrapolate which button has been pressed.

[Shane] went on to implement this control technique using an AVR chip in place of the  radio base unit. He used the data gained from measuring the pulse behavior using an oscilloscope to write the firmware for the project. He filmed a bit of a demo after the break which shows his findings.

We’re not quite sure how this would translate into your own home-brew projects, but the thought of scanning a keypad with two pins of a uC is quite desirable. Sure there is the 555-timer frequency technique, but we’re always down with new ideas.

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