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Topic: reading a voltage (Read 429 times) previous topic - next topic

Gadget999

have a AVR board that is not an arduino

if i send 5v to one of the analogue channels it outputs a voltage in MV

ie  5v = 5000

however if i send it 5v i get 3600   :--   3.6 v

i have also noticed that the board is reading 177 mv when it is ov  (gnd connected to signal)

what am i dong wrong ?

where is my voltage going !


johnwasser

Sounds like the wiring of your non-Arduino doesn't match the software.  Perhaps you should ask the vendor of the non-Arduino or the person who wrote the software.
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CrossRoads

What processor does it use? What is Aref set to? Are you using the internal voltage reference?
You really need to provide more info.

How are you applying 5v and getting two different readings?
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Gadget999

hi guys

thanks for your suggestions - it appears the channel is -2..5 to +2.5 volts !

what is the easiest way to read the 5v ? a voltage divider ?

johnwasser


thanks for your suggestions - it appears the channel is -2..5 to +2.5 volts !
what is the easiest way to read the 5v ? a voltage divider ?


If your 'channel' reads -2.5V to +2.5V how do you read 3.6V for 5V?

If you can accurately read values between -2.5V and 2.5V you can use two equal resistors (about 10K Ohms) to divide your 5V signal in half.  Connect your signal to one resistor, the other resistor to Ground and both resistors to your analog input 'channel'.
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Gadget999

thanks guy - it looks like there must be a zener on the inputs protecting them

i did exactly as you suggested and built a voltage divider - all working good !

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