Posted by: sebion | June 25, 2012

The new SMD sensorboard soldered

I just wanted to show you the next generation smd sensor board in it’s very flat and small smd fashion:

yes it fits the keys 🙂

it hast a backside

and is this flat (about 5 mm)

“OH PLEASE, may I play it?”



  1. Hi, this is very cool, do you have the schematics?

  2. I’m doin quite the same project for my grandpiano at the moment. I dont get, why you need such a big µC and two Cupper sides? I just use a Attiny86. Can you tell me, what for the trimmers are? Do you want to make sure every sensor (voltage divider) has the same range? Why dont use a solution in software? And what for do you need 10 pin connectors? I need 4 (+5V, Ground, and a Bus).

    • I am using the atmega32 because of the 32k flash size. Each controller runs a physic-engine that calculates the hammer movements driven by the measured key movement. I am using two copper sides, as you need that when using an smd controller (I didn’t want to solder that many wire straps). Of course you can build this with through hole parts as well, but then you might get trouble with the space available under the keys.
      When I worked with the cny70 sensors, I found out that their sensitivity strays within a range of lets say factor two and the trimmers were intended to correct this. Of course you can adjust this by software as well (basicly thats what my software does anyway, but that involves a loss of accuracy, so I decided to have trimmers. Finally I found out the new sensors worked well without turning the pots)
      I need +5V, GND. SCL, SDA, and a sync line to make sure the switching scheme of the IR leds are synchronized. This is necessary to avoid crosstalk between adjacent keys.
      Finally I have reserved 4 pins for SPI programming (reset, MOSI, MISO, clock) the board when it got manufactured. So I needed 9 pins and decided to buy a 10 pin solution. The SPI is only connected on one side of a board, of course. The conectors I use are helpful to compensate errors in the octave width as well (the boards can be shifted for about 1mm)
      I hope I have answered all your questions.

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