Is it possible to detect multiple analogue signals from different analogue sources onto 1 analogue input pin on a micro controller.
Another way of asking this question is that we can detect multiple digital signals from a single analogue input by attaching different values of resistors to each digital input source and then when a digital source is activated the specific voltage can be detected using an analogue input, so similarly would it be possible to detect multiple analogue voltages using a single analogue input pin on a micro controller?
Electronic – Measuring multiple analogue signals on 1 analogue Input
adcmicrocontrollermultiplexer
Related Solutions
Although a passive solution is possible, often depending on your source impedance and ADC input impedance, it's usually a good idea to use an opamp for the level/gain shift. One option is an inverting circuit such as this:
Simulation:
The benefit is a very low output impedance to drive the ADC (many ADCs require a minimum signal impedance of <10kΩ)
The input impedance is just R3 (133.2kΩ in this circuit) To prevent loading effects, you want your signal impedance to be less than 10kΩ or so. If it's higher, you can increase R3 and R2 to increase the input impedance (as long as the ratio remains the same, so does the gain)
Some opamps don't like a gain less than 1, so you need to check the datasheet to make sure it will be stable in this configuration. Also a small capacitor across R2 is usually a good idea to control bandwidth appropriately.The readings will be inverted, but it's easy to correct for this in firmware.
A quad opamp with a decent voltage reference IC and divider to provide the 735mV reference for all non-inverting inputs could be used. The opamp must be able to swing its output down to ground; some op-amps cannot do this, so check the datasheet.
For the I2C and MAX127 (which looks fine) option, you could use a level shifter IC to convert between the 3.3V and 5V levels needed. There are quite a few such ICs designed for use with I2C. Have a look on Farnell, or Mouser, Digikey, etc. The PCA9306 is one example.
SPI uses "standard" outputs which are driven high/low (as opposed to I2Cs open drain) You can also easily level convert this, since each line is only one direction. A couple of transistors can be used.
Zener is an OK way.
Or consider a resistor P1 to ground to reduce range of V at pin.
eg adding a 680R P1 to ground will reduce sensitivity.
Lower R = more reduction.
Too low = no operation.
Best Answer
It depends on the signals. If they are for example sinusoids (of different frequencies), then you can do a [fast] Fourier transform and find them. For arbitrary signals, I think the answer is no. You need to clarify what you mean by signals.
This is not the same problem as in your previous question. Here you have multiple input pins via the resistors and you differentiate the signals (presumably of the same amplitude) by giving them different amplitudes using your resistors.
This is more or less a repeat of your 1st question. If you ask however whether an arbitrary DC sum can be detected/split: the answer is obviously no. How could you tell the difference between 1V+1V and 0.5V+1.5V by just measuring the total/sum?