Hi there!
I've been programming with Arduino in the past, but now I want to apply it to my graduation project. The main challenge is that I want to combine several analog inputs, but I don't have space for a multiplexer. Is it possible to delay the signal from my sensors to read them one after another on my analog port?
I want to connect four potentiometers to one analog input. In the setup below I combine it with four capacitors. Would this work? And what kind of capacitors would I require?
There's no way this approach can work. For one thing, how can you tell which pot you're reading?
If you only have one analog input you can use an analog mux - eg a 4066 , 4051 etc to select the pots , but you'll need several digital outputs to drive the mux.
Can't you find some more analog inputs?
Allan
Is it possible to delay the signal from my sensors to read them one after another on my analog port?
It is but not that way. You would need more electronics to do that than using a multiplexer.
What puzzles me is why you think that circuit would do anything. How do you think it could work?
My idea was to give all inputs a different delay using the capacitors. Four different capacitors would delay the signal each a little more. First comes in the signal from potmeter 1, then potmeter 2, etc. But according to your responses, that will not work. I will change my design, include a multiplexer and try to get it work that way. Thanks for the responses!
Ok I think you don’t understand how capacitors work.
Hi,
Tymo ... you are graduating on what?
Regards.
How many pots/analog signals do you have?
The Mega has 16 analog inputs and the Uno has 6.
...but I don't have space for a multiplexer.
I've caused myself lots of trouble trying to make things small. Big manufacturers are very good at it, but it's not as easy for a hobbyist.
I think you might be struggling for the notion of a sample/hold circuit per input - that's more
circuitry than a multiplexer.
The easiest multiplexer to use is the one on the chip that handles all the analog inputs - have you run
out of analog inputs?
You could combine the inputs by summing them, arranging each input to pass though two
resistors in series, the mid-point being shorted to ground using a digital pin for each input you
don't want to sense. The problem with this is it assumes low (or at least constant) impedance sensor
outputs (which potentiometers are not), and reduces the sensitivity by a factor of 2x4 anyway (2 for
the two resistors in series, 4 for the 4 channels).
The other approach is to drive both ends of each pot from digital pins, a total of 8 pins, and float all the
pots you want to ignore by setting those pins as INPUT... I expect that's too many pins though.
TimoDy:
The main challenge is that I want to combine several analog inputs, but I don't have space for a multiplexer.
Nonsense. 
Simply nonsense. 
Multiplexers are smaller than potentiometers.
I agree with others that this is not a viable approach. Others have suggested what might work so I'll take a stab at what you might be thinking with your circuit and explain why it is not a valid approach.
I going to assume you are switching the 5V shown in your diagram ON and OFF. And that you were expecting to measure the rising voltage shortly after turning the 5V on. Hopefully deducing what the pots are doing.
The issue is: because all the pot wipers are connected together they will interact. So mathematically there is no one single solution for a particular set of pot settings.
Ergo you cannot know where the pots are set by this measurement. This is true even if you take enough readings to capture the whole rise time of point A0.
