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Nick Gray

 

Nicholas Gray

Nicholas has worked in the Semiconductor industry for over 30 years and has authored a number of published articles about data converters (ADCs and DACs) and signal integrity issues.

 

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  • Hi

    I have a project that reads 4 air pressure sensors, performs some calculations and displays the values on 4 seven digit displays.

    To complete the project, I want to include a 6 position rotary selector so I can select different algorithms that the code can apply to the Analogue values coming from the sensors.

    The way I thought of doing this is to connect 5v to the Selector with different resistors on each of the 6 output pins. Then the Arduino would check the voltage to determine which position the selector is at.

    Problem is that I have used up all 6 analogue inputs.

    I guess I could use one of the free digital pins and use an analogue to digital converter but I don’t have a lot of space to be adding more boards. Is there some other way I can do this?

    Most of the digital pins are free.

    Thanks in advance

    Sam

Reply

  • Hi

    I have a project that reads 4 air pressure sensors, performs some calculations and displays the values on 4 seven digit displays.

    To complete the project, I want to include a 6 position rotary selector so I can select different algorithms that the code can apply to the Analogue values coming from the sensors.

    The way I thought of doing this is to connect 5v to the Selector with different resistors on each of the 6 output pins. Then the Arduino would check the voltage to determine which position the selector is at.

    Problem is that I have used up all 6 analogue inputs.

    I guess I could use one of the free digital pins and use an analogue to digital converter but I don’t have a lot of space to be adding more boards. Is there some other way I can do this?

    Most of the digital pins are free.

    Thanks in advance

    Sam

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  • in reply to Former Member

    Hi, Sam –

    I am sorry that I did not see your question sooner, but I cave a couple of solutions for you. First, realize that it is not necessary to use a board level ADC as many ADC chips are easy to use. One example is the SPI output ADC081S021. I can suggest a complete circuit, if you need it.

    Another solution is to use a string of 12 resistors with 6 voltage comparators. I know of only one device with six voltage comparators in it and that is the LMV7231 from TI. However, there are a few quad voltage comparators available and you can use two of those. The arm of your selector switch would be connected to the non-inverting input of all voltage comparators. The series resistor string would have 13 nodes, numbered 0 through 12, with node 0 at ground and node 12 at perhaps 5 Volts. The even nodes 2 through 10 plus ground are each connected to separate pins of the rotary switch and the odd nodes are each connected to the inverting node of separate voltage comparators. As higher voltages are selected, more and more comparator outputs go high.

    Other topologies are possible, but I think these two provide the fewest components.

    Nick Gray