AttoPilot Voltage sensor question

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prefetch
Posts: 1
Joined: Sun Dec 10, 2017 9:26 pm

AttoPilot Voltage sensor question

Post by prefetch » Sun Dec 10, 2017 9:32 pm

hi guys.

the 180A version of this product says in the data sheet that "You may use this sensor directly with a 5V ADC" if you want to get to up to 60V instead of 51.8V.

https://cdn.sparkfun.com/datasheets/Sen ... Output.pdf

since my application is using 7s batteries, fully charged i'm up around 58 volts, and i'd really like to use this sensor, but i'm not really sure how to use this sensor "directly with a 5V ADC".

does anyone understand how i'd go about doing this?

paulvha
Posts: 129
Joined: Sat Nov 11, 2017 2:39 am

Re: AttoPilot Voltage sensor question

Post by paulvha » Mon Dec 11, 2017 7:10 am

Actually this is a straight forward calculation. The input voltage is monitor(at 50V) with a voltage divider of (4.7K + 10K) over 1K resistor. Hence the output analog V, with 50V on Vin = (50 / 15.7) * 1k = 3.18V. If you have an ADC that can handle max 3.3V, that is directly connected to analog V, you should NOT increase the Vin to more than 50V otherwise you damage your ADC. If you have an ADC that can handle up to 5V (like arduino), the upper limit of 60V is determined by the limit of the INA169 (as it can not handle higher). The maximum output at 60V is 3.8V.
However if you have an ADC that can handle up to 3.3V you can could connect the analog V output to a 1K resistor, connect the other side of that resistor to a 4.7K resistor AND the ADC input. Connect the other side of the 4.7K resistor to GND. The maximum voltage to the ADC will be (3.8 / 5.7K) * 4.7= 3.13V. The standard 0.25W resistor versions should be sufficient.

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