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I'm in the planning stages for a project using the Arduino Uno to control 8 distance sensors, and have run into a little road block, the Uno only has six input pins. So I'm wondering, is there any way for this to work? If so, how?

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There's more than one way to do it (TMTOWTDI).

There are a several ways to connect 8 analog inputs to an Arduino.

  • Add an analog multiplexer, as georgebrindeiro suggested. Such as: (a), (b), (c), (d), etc.
  • Replace the Arduino with one that has enough analog inputs already built-in. Such as the Arduino Mini with 8 analog inputs, the Arduino Due with 12 analog inputs (b), (a) the Arduino Mega with 16 analog inputs (b), the Teensy 3.0 with 14 analog inputs (c), etc.
  • Add one or more external ADCs, and connect it to digital pins of your CPU. Such as: Arduino 4-20mA Shield with 16-bit ADC (a); ADS1115 16-Bit ADC -- with 4 of these boards, 2 digital pins from the Arduino are used to read 16 analog inputs (b); MCP3208 8 channel 12 bit SPI ADC (c); 8-channel 16-bit Raspi analog board (d); Arduino and the LTC2440 24bit ADC (e) (f); "The Brick" 8 Single Ended 16 Bit Analog Inputs (g); etc.

p.s.: Multiplexing analog inputs requires an "analog multiplexer" -- most multiplexers are "digital muxes" which won't work with analog inputs.

p.p.s.: All the ultrasonic distance sensors I've used only require digital I/O pins. What kind of distance sensors are you using?

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  • $\begingroup$ Of course! your right, they only need i/o, thanks! $\endgroup$ – Dylan Katz May 6 '13 at 18:31
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Whenever you have more signals than appropriate inputs in a digital system, you likely need a multiplexer or simply mux. An M-to-N mux is a circuit that enables you to select which of M input signals you want to output to N mux outputs, usually using digital pins to make that selection.

Googling quickly, I found this solution for the Arduino Uno: a Mux Shield. Hope that helps!

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