Powering arduino uno through Vin pin

Thread Starter

khizer ali

Joined Jan 10, 2019
21
hello, i am powering arduino uno using Vin and GND pins. I am monitoring sensors values through analog pins of arduino uno. I am supplying 7-9 volts. My question is that if my input voltages changes (e.g 8 to 7) ,Will it affect my sensor readings?
 

dendad

Joined Feb 20, 2016
4,167
If your sensors are running from the +5V generated by the Arduino, the readings should not change.
But if you are running the sensors from the Vin, they may. It does depend on what the sensors are and how they are wired.
You will need to submit FULL circuit info to get a better answer.
 

Reloadron

Joined Jan 15, 2015
6,693
hello, i am powering arduino uno using Vin and GND pins. I am monitoring sensors values through analog pins of arduino uno. I am supplying 7-9 volts. My question is that if my input voltages changes (e.g 8 to 7) ,Will it affect my sensor readings?
If I read you correctly no would be the answer. If you look closely at your Arduino UNO board it should look like the below image:
Arduino PWR.png

The external power connector goes directly to a voltage regulator and the onboard regulator outputs to a few filter capacitors. The 2 volt difference between USB (5 Volt) power and the needed 7 to 12 volts external power is allowing 2 volts for the dropout of the regulator. If the external voltage drops below 7 volts you may start seeing problems but as long as the external voltage is between 7 to 12 volts things should work fine. I have also seen some run on as high as 15 volts but I would keep it between 7 and 12 volts, if it varies a little it should not matter.

Ron
 

Thread Starter

khizer ali

Joined Jan 10, 2019
21
If your sensors are running from the +5V generated by the Arduino, the readings should not change.
But if you are running the sensors from the Vin, they may. It does depend on what the sensors are and how they are wired.
You will need to submit FULL circuit info to get a better answer.
No, I am powering the sensors through external power supply.
 

dendad

Joined Feb 20, 2016
4,167
What are the sensors?
If they derive their excitation relying on the supply voltage then the output may change with supply variations. So without the info on the sensors it is not a question that can be fully answered.

For instance, if you have an LDR running from an external voltage to an analog input then to gnd, if the external supply changes, so will the reading.
But usually, an I2C or OneWire sensor has its own internal regulator so that is ok.
 
Last edited:

Wolframore

Joined Jan 21, 2019
2,549
If your sensor is 5V or 3.3V, does not require high current and is place fairly close to the Arduino. It's better to power from the Arduino as you will then get a ratiometric reading.
 
Last edited:

djsfantasi

Joined Apr 11, 2010
8,390
What are the sensors?
If they derive their excitation relying on the supply voltage then the output may change with supply variations. So without the info on the sensors it is not a question that can be fully answered.

For instance, if you have an LDR running from an external voltage to an analog input then to gnd, if the external supply changes, so will the reading.
But usually, an I2C or OneWire sensor has its own internal regulator so that is ok.
And that’s why I asked which of the two power supplies he is changing. It’s an important piece of data that’s unknown.
 

dendad

Joined Feb 20, 2016
4,167
It is another case of trying hard to find out the info needed for a good answer. I wonder why it is many TSs seem reluctant to answer these questions?
 
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