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Topic: sensor box using a single analog input (Read 907 times) previous topic - next topic

rangua

hi, i'm not sure if this is the right board, but i thought some of you might have had this worked out and could point me out to the solution.
I'm building a garduino project, and i wanted to take a measurement to many different pots to analyze better the data. The problem is, i have only so many analog ports, and i don't really think a bigger chip is quite worth it since the measurements don't need to be simultaneous.
I thought about this circuit using npn transistors as switches. would my measurements be affected by the other sensors?
i put the transistors in between the supply and the sensors because prolonged powering of the sensors builds up rust and what not, i'd prefer to use them when i read them and no more. Do you think i should add a couple transistors after the sensors too to isolate the measurements?
thanks.

rangua

woopsie i forgot the schematics.
the circles are meant to be the connections to the arduino. the leftmost circles are the digital pins and the rightmost circle is where i plan to plug the analog pin.
oh yea, and i want  to measure the values of R3 and R4.

rangua

bump..
moving the thread to sensor board
http://arduino.cc/forum/index.php/topic,129979.0.html
i think that board is more appropiate. please answer there

draythomp

Funny how the experts haven't chimed in here.  There are some folks on here that could really help you with this.  Maybe if I say something stupid they will chime in with a correct answer to help you out.

Here's a person that had the same problem and how he solved it.  Could be much cheaper and easier than other methods

http://miscellanea.com/how-to-get-more-arduino-analog-inputs/

Trying to keep my house under control http://www.desert-home.com/

rangua

hmm. that sounds like a good option.
i'll check on that IC and hopefully i can buy it where i live. it's probably gonna end up being cheaper than buying one transistor for each analog.
it would be nice tho to know how to build this without using an IC. i don't know why but i'm sure there is a way to do it.

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