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Topic: connecting many sensors- feasibility (Read 786 times) previous topic - next topic

dgbit

Hey!
i have to decide whether what i want to do is possible and i need some guidance. i need whether anyone did that or have examples that it is done.
i want to connect approximately 256 sensors to arduino. i tought i can do that with  multi layered muxes, but i have concerns about
- driving the 256 sensors, how can i manage the current and the volt? those sensors i have seen was generally connected as alone to arduino.
- reading 256 sensors one by one , do i loose real time efficieny
- all the sensors have analog outputs, require approx 5V VCC.
- is it possible to demux the volt too? has anyone done that ? or would it be not feasibel since after you applythe volt it iwill require a set up time to sense.. i mean i can not probably just apply the volt and try to read the output ?
- is there examples for this , a reliable chip which already deals with current volt output selection and you just connect the sensors to that chip

input is blow, air flow on a surface.. i want to know whichpart of the surface is blown into.. open to suggestions.
and i will also put alcohol sensor sparingly to detect alcohol in blood.

johnwasser

It takes about 100 microseconds to read an analog input so 256 of them would take at least 25.6 milliseconds or about 40 reads per second.  That sounds feasible.  You'll need time for setting up the address for the analog multiplexers but that should not be too bad.

If the sensors draw any significant amount of power you will need a separate 5V supply for them.  Add up all the power requirements to find out how big a power supply you need.

If you want to do something fairly simple, like figure out where the greatest airflow hits the wall, the calculations will be fairly simple.  If you want to forward all 256 values to a PC for analysis you might be spending more time sending the data.  If you send five characters per value you will have to send at 512 kilobits per second to keep up with that rate you can read.
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