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Topic: what is the maximum number of analog input channels possible? (Read 833 times) previous topic - next topic

fabienLyrique

I am thinking about buying an Arduino but need 28 separate analog sensor channels. Is it possible to hook up two of these multiplexers to an Aduino?

http://www.sparkfun.com/products/9056

retrolefty

Yes, it will require the use of 6 digital output pins and one analog input pin, but it will work.

Lefty


fabienLyrique

cool. So just to clarify, I can use an ATmega328 chip on my own baord with an external crystal, 2 multiplexers, taking up a total of 8 of the digital pins and 2 of the analog pins, AND still be able to connect my Bluesmirf bluetooth module as well, through the (PCINT17/TXD) PD1 pin 3? This would give me 32 analog inputs wirelessly. Is this all possible?

liudr

Sometime ago sparkfun showed off this shield they made with enough analog inputs you need:

http://www.sparkfun.com/products/9832

It is a shield so it secures nicely above your arduino. The board you pointed out has no mounting holes. It's gonna sit and rock and slide around.

fabienLyrique

very cool! thanks for the lead. But I could always solder the multiplexers to the board and attach is to a self-made hub - that way it would be cheaper to buy... Also, can I use my USB RS232 analog to serial converter to program it, using the Arduino IDE?

retrolefty


cool. So just to clarify, I can use an ATmega328 chip on my own baord with an external crystal, 2 multiplexers, taking up a total of 8 of the digital pins and 2 of the analog pins, AND still be able to connect my Bluesmirf bluetooth module as well, through the (PCINT17/TXD) PD1 pin 3? This would give me 32 analog inputs wirelessly. Is this all possible?


It should be all possible. Not fimilar with the bluetooth module. The two mux boards can share four of the digital output pins (to select which of sixteen inputs to select) and can share one analog input pin (wire them to the same analog output of each mux) if you wish, but using two analog input pins (one for each mux board) is OK also. Then two more digital output pins are used to enable each mux, one at a time. So total pin count to support 2 mux modules is SIX arduino digital output pins and one or two analog input pins.

Your sketch would output the channel number to select, 0-15, on four of the output pins. Then select which module to select using two of the digital output pins (0-15 module or 16-31 module). Then perform a analogRead() statement to read the select analog voltage.

Lefty



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