Note that by itself, this project can only provide Gate signals and voltages responding to pressure being applied to the pads. There are no musically pitched voltages generated. That must be handled by external circuitry such as the Programmer/Sequencer.
This keyboard may be made with as many keys as you like, though the value of RPD (15k) may have to be made smaller as more keys are added. Each key provides for touch proportional voltage and pulse outputs. The pulse output stays high for however long the key is touched. In the schematic, each stage's touch voltages are combined through a diode network resulting in an output dominated by whichever key is touched hardest. This function is optional, but is useful if you wish to use the keyboard (in conjunction with Programmers) to play melodies with touch control of their dynamics.
How to use this module:
The keyboard may be built and installed to fit any flat surface, for example, the body of an electric guitar. Make sure that all components are mounted in close quarters with the touch keys. Wiring should be kept tight. Note that the pattern surrounding each key should be grounded. Connecting your touch responsive keyboard with a Programmer will result in an exceptionally powerful unit, able to access as many presets as you want at a touch. This means too, that your keyboard will be able to perform non-tempered scales since each of the keys can be preset to a different tuning.
A little on how it works:
On the CGS86D Driver PCB: The transistors make up an emitter coupled astable oscillator with a somewhat distorted square wave output of about 100kHz.
On the CGS86 Detector PCB: The first amplifier for each of the two stages shown a full wave rectifier and filter whose output goes positive as more of the 100 kHz is shunted to ground by touching a key. The second amplifier provides the pulse output.
The circuit may be operated with +/-12 or +/-15 volt supplies, although the output voltages will be higher on the higher supply voltage.
|The schematic of the Serge Touch Responsive Keyboard. The portion to the left is on the sub board CGS86D, while the touch-pad detector circuits are in groups of eight on the CGS86. The touch-pads themselves are on the CGS86PAD PCB.|
|TOP EDGE CGS86|
|+VE||wire to +VE pad on CGS86D|
|0V||Shield connection for wire running to touch-pads. (8 off).|
|TP||Core connection for wire running to touch-pads. (8 off).|
|PLS||wire to PSL pad on CGS86D.|
|BOTTOM EDGE CGS86|
|GATE||Individual touch pad Gate output (8 off).|
|0V||wire to 0V pad on CGS86D|
|0V||0V/GND connection for optional/general use. (8 off).|
|CV||Individual touch pad Control Voltage output. (8 off).|
|VO||Combined CV output for connection to VO pad on CGS86, or for cascading to another CGS86. (2 off)|
|GO||Combined CV output for connection to GO pad on CGS86, or for cascading to another CGS86. (2 off)
note: on CGS86 VER1.0 one GO pad needs a link to work as its track is missing.)
|CGS86D Driver PCB|
|-VE||negative voltage power rail out, for external use if needed.|
|0V||wire to 0V pad on CGS86|
|+VE||wire to +VE pad on CGS86|
|PLS||wire to PSL pad on CGS86.|
|VO||wire to VO pad on CGS86. (2nd pad for connection to second CGS86)|
|GO||wire to GO pad on CGS86. (2nd pad for connection to second CGS86)|
|CCVO||Common CV Output. This is the pressure CV, and will equal the individual CV output of the hardest pressed touch pad.|
|CGO||Common Gate Output. This will go HIGH any time a touch pad is touched.|
Specs & Downloads
Specs & Downloads