hello ! i am using 4 sensors like pH,TDS,TURBIDITY ,TEMPERATURE and all these are connected to analog pins of arduino uno .All of these sensors require 5V DC. Today I used 12V DC battery and connected a buck power supply module lm2596, and set the output to 5 v dc. After connecting sensors ,multimeter still showed 5V , But the sensor output values are very different , i am unable to fix it...

please suggest a solution , is it a problem with buck module or there is any other problem ..

Thanks
Regards

 

Depending on the excitation current of your sensors you could have likely supplied them using the Arduino Uno. The 5 volts out is capable of 500 mA to upwards of an amp. That assumes you are using 12 volts to the Arduino Uno external power pin.

When you did this are all the gtounds common to each other and the Arduino? The analog inputs of the Arduino rely on the V reference. When I use my Arduino Uno board powered over the USB port my USB 5 Volts is only 4.9 volts making my A/D reference only 4.9 volts so in this case my 4.9 volts is 1024 bits since it is V reference. If I use an external 12 VDC for power my boards on board regulator outputs 5.00 volts and all my analog input readings shift accordingly. I have no idea how yours is setup. You can also include code to use an external V reference.

Ron

 

You’ve lost the ratiometric accuracy of sharing the same 5v supply. Either use the 5v buck supply AREF, to do this you will have to set this or supply the Arduino with the buck supply as long as you have enough current available.

 

This is the case where you show what you did. Telling us is a waste of time.