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February 15, 2011
about 4 years ago
With some I2C devices there are more addresses available, but this chip has only has three. So, you’re limited to three per I2C line. It’s possible you could use an arrangement such as two 8 channel multiplexers, one for the data line and one for the clock line, and have 3 devices on each channel of the multiplexer.
For what reason do you need so many sensors?
If you have access to an oscilloscope you could look at the signal coming off SDA. Otherwise, I would suggest trying to write a value to a register on the sensor and then read it back. If it’s coming back as 0x00 or something other than what you wrote to that register, then you can definitively make the statement that something is amiss.
You make your own. They’re typically pads on a pcb, or a matrix of Indium Tin Oxide (or Aluminum Zinc Oxide) traces that are deposited on the inside of the glass covering a display screen, as in the case iPads, iPhones, smart phones, etc.
All you really need is a wire connecting to a conductive material. I’m currently using thin copper sheeting. Some people use aluminum foil with an alligator clip connecting the foil and the wire. It all depends upon your application.
The Wire library for the Arduino is not so great, and I would recommend directly using the AVR example.
As far as the epoxy is concerned, it’s fine. It has a dielectric constant of approximately 4, but your biggest issue will be air bubbles trapped inside the epoxy. If you can get those out you’ll have fairly uniform results. For proximity sensing, your best bet will be to have a large electrode, the largest charge current (63 uA) and the largest charge time (128 ms) of this sensor. If you have big enough electrodes, you need not use the proximity sensing mode of this sensor, which essentially ties all electrodes together to act as a proximity sensor.
For a beer pong table, if you expect to detect the ping pong ball when it lands inside the cup, forget it. The change in capacitance would be so small that you wouldn’t be able to separate it from the noise. A full cup verses an empty cup, however, is doable. The calibration is the hardest part in working with these sensors.
about 4 years ago
I received mine last week and am quite please, but I would like to comment on the awkward placement of the I2C lines. Considering the large number of these you have in stock, I won’t suggest you run out and redesign the board, but please consider in the future revising the board to make these pins more easily accessible for those of us doing breadboard prototyping.
Yes, but you’ll need to very carefully cut one of the traces on the back of the board. On the bottom of page 3 of the datasheet they specify what’s required to change the address. Just connect the address pin to VSS, VDD, SCA or SCL to change it.
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