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Author Topic: How to measure a temperature value of 5V?  (Read 497 times)
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Hi dudes,

i have a temperature sensor with a output range of 0... 5V (0-50°C). Unfortunately, the arduino due had an maximun analog input of 3,3V. How can i handle it? Voltage divider?

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I think you answered your own question.
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I think you answered your own question.

OK, thats makes me happy ;-)

I have chosen two 5k resistors, so I've always get the half of the applied voltage. As smoothing I've put a 10nF capacitor at the loaded dividers. Is that correct or redundant?

After i get the value of the voltage divider, can i "quick a dirty" multiply the current value with two in my code?


* voltage divider.jpg (49.76 KB, 1040x594 - viewed 21 times.)
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After i get the value of the voltage divider, can i "quick a dirty" multiply the current value with two in my code?

Short, yes.
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Generaly it will works.
But actual integrated circuit are never equivalent to a perfect voltage source. There is allway a parasistic serial resistor (Rs)  inside the IC.
Generaly this parasistic resistor is very small but by security I would have a look on the datasheet.
If Rs = 1 ohm it will not affect the calibration of the voltage divisor, but if Rs = 2 kohms the top resistance will be equivalent to 2k + 5k ohms and the ratio of the voltage divisor will be modified. R= 5( 2+5 +5)= 0.416.
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Generaly it will works.
But actual integrated circuit are never equivalent to a perfect voltage source. There is allway a parasistic serial resistor (Rs)  inside the IC.
Generaly this parasistic resistor is very small but by security I would have a look on the datasheet.
If Rs = 1 ohm it will not affect the calibration of the voltage divisor, but if Rs = 2 kohms the top resistance will be equivalent to 2k + 5k ohms and the ratio of the voltage divisor will be modified. R= 5( 2+5 +5)= 0.416.

Yes you are right, if we know the Sensor ZDFuino works with we can my predict better with what he has to fight to get it working. Some works with 3,3V to, but then he may get some resolution issues (btw. scaling the 5V to 3,3V down is better then cut it to half for the resolution, and with an Z-Diode for the Input-Pin in the wiring there is an better safety for the Due).

In my Opinion Sensors with Current output are an better solution then Sensors with Voltage output there is no mess with resistors.
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