18 Analog Inputs

Community Projects
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My goal is to read 6-three axis accelerometers simultaneously in the most cost efficient way possible.

Let me preface this by saying I’m very new to all of this and I have done some searching both through google and the forums and there is tons of information there, I just don’t understand it. I have a pretty decent understanding of most things in the computer science area but board level stuff is something I’ve just recently started learning.

I was looking at the Leonardo due to it’s cost but realized it only has 6 analog inputs which would mean I would need three separate boards to read all of my sensors. I know there has to be a way to utilize more analog inputs with the use of ADC’s or DSP’s(I understand what these do just not HOW they do it, yet). I was also told another issue I may run into with arduino’s is the way they process the information and that buffer is an issue.(I understand what buffer is, but not how it works).

Then there is Raspberry Pi, which has no analog inputs but much better processing power, once again I’m sure that I could use some sort of converter or processor to make it work with the Pi.

Any tutorials or places I could learn about this more would be great. While I am looking for someone to explain to me the best way to achieve my results, I also want to be able to understand their answer.

(If it matters three of the sensors will be reading vibration on lower rpm equipment ~25-400rpm, and the other three on higher rpm equipment ~1500rpm. This is very large equipment, the high speed bearings probably weigh close to 75lbs a piece)

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  1. Simultaneity does not exist. There is always a time difference. How much timing skew can you afford?

  2. What ADC measurement resolution do you want? Since you’re talking Arduino I assume 10 bits is enough?

  3. How fast do you need to sample the signals?

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jjones9:
I was looking at the Leonardo due to it’s cost but realized it only has 6 analog inputs which would mean I would need three separate boards to read all of my sensors. I know there has to be a way to utilize more analog inputs with the use of ADC’s or DSP’s(I understand what these do just not HOW they do it, yet).

You can use something like the CD4051 to multiplex your analog inputs. Each CD4051 will allow you to connect eight sources to one analog input. As lyndon mentioned, there is no such thing as reading all inputs simultaneously. Even the Arduino uses a mux internally... it only has one ADC.
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Why does it have to be analog? There are also accelerometers that measure themselve and communicate data over I2C or SPI protocol. That has a steeper learning curve, and also introduces latency. (But any ADC would too) However it would lessen the analog input requirements.

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Typical Arduino stuff poorly suited for this application. Look at the Teensy 3.1