Finished Pieces

Space Keyboard


    What’s really cool about this keyboard is that it has a flashing light display behind the airbrush space scape above the piano keys. The display is made up of 5 lights that flash in order from left to right and back.

    The light controller circuit is an isolated circuit with it’s own rate control adjustment separate from the clock speed of the keyboard sound circuit.

    In many cases you can take the signal which is being used to power the light and redirect it (through a potentiometer…usually 10k or so) to the pitch control of your toy to make a crazy pitch modulating LFO type effect….which is what I did here.

    By modifying the built in light sequencer circuit I was able to build a cool little melody sequencer.

    -First I installed a rate adjustment for the light cycle.
    -Then I took the wire sending electricity to each of the LEDs and wired each one to a potentiometer.

    -Then each potentiometer was wired to the keyboard pitch control.

    By adjusting the individual potentiometers it is possible to program simple 5 step sequences.
    It’s a very simple bend and a very cool sounding effect.

    This keyboard contains five separate circuit boards.
    -Control interface board
    -Keyboard audio circuit
    -Power/amp board
    -“space” sound fx circuit
    -Blinking light sequencer circuit

    The largest one is just the CONTROL INTERFACE. This holds all of the
    function and piano key buttons. This connects to the keyboard audio
    circuit with a ribbon cable.

    The KEYBOARD AUDIO CIRCUIT is the keyboards “brain”. It processes the
    pushbutton matrix (signals from the control interface board) and generates
    the main keyboard audio signals. There is a trim pot on this board which
    controls the keyboard pitch.

    This circuit is connected to the POWER/AMP BOARD with another ribbon
    cable.This mixes the keyboard audio signal with the “space” fx signal and
    sends the signal to an amplifier. It then takes that signal and sends it
    to a simple envelope follower type circuit which powers the light
    sequencer circuit in conjunction with the amplitude of the audio signal.

      The LIGHT SEQUENCER circuit receives an incoming signal from the
      voltage/amp board and activates five different lights in sequence. The
      rate of the sequence can be adjusted by removing a resistor from the board
      and replacing it with a 1M potentiometer.

    The “SPACE” FX circuit is a completely separate circuit. Both the pitch
    and volume of this circuit can be adjusted independently of the keyboard.

    PITCH CONTROL
    You can make some pretty crazy warbling, screeching sounds by lowering the
    pitch. It also does some cool stuff when you raise the pitch. Raising it
    to the right level will create amazing glitch effects that work extremely
    well with the drum beats and demo songs.
    The tricky part is that there’s a very small pitch window in which this
    glitch will work and if you turn the pitch up too high, the circuit will
    crash. For this reason, I built in coarse, mid and fine tune pitch
    adjustments. This allows the user to very finely adjust the pitch and take
    advantage of the glitch feature. I also added a pitch calibrating board
    for fine tuning the pitch range so that it can’t be turned too high or
    low.


    LIGHT SEQUENCER

    The light sequencer circuit board outputs a voltage signal to each of the
    five lights in sequence (one at a time) when the keyboard is making sound.
    By taking the signal which powers the lights and routing that to the
    keyboard pitch control pin, you can modulate the pitch. Unfortunately the
    signal cannot power the light AND change the pitch at the same time. It
    CAN but there are lots of problems that are caused by doing this (just
    trust me). Because of this I installed a button which switches between
    “light mode” and “pitch mode”.
    Each of the five steps of the sequence has an on/off switch and a pitch
    control adjustment. I also added a sequence rate adjustment and a total
    pitch depth adjustment.
    By setting each step adjustment to different points and switching the
    sequencer to “pitch mode” you can make some interesting modulated
    sequences.

    “REPLAY” TRIGGER
    The keyboard has a built in record and replay feature. This allows the
    user to record short melodies and play them back.
    I added a circuit to the keyboard that allows the user to trigger the
    “replay” function using an external controller. There are two input jacks.
    One is for a switch, like a foot pedal, the other is for voltage pulse
    signals, like an LFO or gate signal from an analog synth.
    The circuit itself is a simple transistor and opto isolator circuit. The
    incoming signal activates two transistors. One turns on an LED (so that
    you can monitor the incoming signal) the other powers an opto isolator
    which then activates the “replay” function.
    To do this I simply connected two wires to the points on the control
    interface board that are connected to the “replay” pushbutton contacts and
    wired them to the opto isolator.”

    Sounds

    Sorry, no sound files for this piece.

    2 Responses to “Space Keyboard”

    • 1

      Martin Cain said:
      November 30th, 2009 at 1:34am #

      Hey pete I was scrounging the GetLofi archives and found a pretty in-depth chunk of information regarding your modification of this keyboard. The page also contains some sound files. In case it’s helpful.

      http://www.getlofi.com/?p=298

    • 2

      casper said:
      February 18th, 2010 at 1:46am #

      martin:
      wow thanks! I must have uploaded that back in the days before I had a website I could update myself. I used to have to pay someone every time I wanted to upload a new device or anything! times have changed 🙂

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