ADC circuit automation design help

[dashy1981]

Hi,

I have MC with ADC module. Firmware is working fine. For current requirement to measure 9V. I use a voltage divider to bring it down to 5V range and connect to ADC pins.

Now I have new requirement to measure three more voltages... 12 V, 15V and 24 V inputs.

I am wondering if it's possible to optimize the circuit to measure all voltages automatically without using three different stepdown circuits?

Basically the question is that is it possible to use some kind of auto voltage detection and apply suitable voltage step down before connecting to the MC pins?

 

[BobK]

You could make the lower leg of the divider by using 3 resistors connected to different pins on the micro, one for each voltage range. The micro could then select the range by setting just 1 of these pins as output and outputting low. The other two would be set to analog inputs.

Bob

 

[ver chan]

you can use voltage regulator LM78---- series for different voltage output, look at alldatasheet.com for reference

 

[Harald Kapp]

you can use voltage regulator LM78---- series for different voltage output, look at alldatasheet.com for reference

Excuse me, but this is nonsense. A regulator will provide a ´stabilized output and you will loose all means of measuring the input voltage.

 

[ver chan]

Excuse me, but this is nonsense. A regulator will provide a ´stabilized output and you will loose all means of measuring the input voltage.

-------------i guess you are right,.............. but my professor taught us some methodology of electronics experiment, sometimes we just sacrifice (blown, burned, and break) different electronics equipment through experiment just to extract a RELIABLE data, and these data really reveals some DISCREPANCY between theoretical and actual phenomenon on different components,,,this may sound impractical and hazardous, BUT my prof. taught us to rely on empirical REALITY.....more power to you Harald Kapp, ive noticed that you are excellent when it comes to caution and safety measures and its great

 

[Harald Kapp]

BUT my prof. taught us to rely on empirical REALIT

There's nothing wrong with relying on empirical data. However, one should works towards the final goal when troubleshooting or analyzing a circuit. Replacing a variable measurand by a well regulated voltage is not necessarily the best way to do this. A well controlled variable voltage (e.g. from a lab power supply) serves much better.

Anyway, the issue with the op's question is not that the input voltage is variable - that's what he is going to measure. The issue he sees is that the range of input voltages is rather wide and he wants the circuit to be adaptable to different ranges.This is where Bob's answer in post #2 comes into play.

 

[ver chan]

There's nothing wrong with relying on empirical data. However, one should works towards the final goal when troubleshooting or analyzing a circuit. Replacing a variable measurand by a well regulated voltage is not necessarily the best way to do this. A well controlled variable voltage (e.g. from a lab power supply) serves much better.

Anyway, the issue with the op's question is not that the input voltage is variable - that's what he is going to measure. The issue he sees is that the range of input voltages is rather wide and he wants the circuit to be adaptable to different ranges.This is where Bob's answer in post #2 comes into play.

-------ahhh! ok, you explained it more clearly now , thanks for your response