Electrical – Voltage divider to measure 12v battery with arduino low consumption

arduinolow-powervoltage dividervoltage measurement

I want to measure 12v. Car battery with arduino. Three questions:

  1. Is the R1 and R2 the best values? The car battery can go from +10v. To +15v.
  2. How and what can I use to save power between the measure reads? Like a transistor to switch on and off or something like.
  3. Must I add something to protect arduino pin from car battery overvoltage?

I have this:

———————————————— +10v. To 15v. Car battery
         |
         |
    Something here to switch off and save power? 
         |
         |
         R1 = 150kOmh
         |
         |——————————- to analog arduino pin to read voltage 
         |
         |
         R2 = 470kOmh
         |
         |
——————————————————- GND negative battery

Solved!

———————————————— +10v. To 18v. Car battery
         |
         |
         R1 = 36kOmh
         |
         |———————————————- to analog arduino pin to read voltage 
         |            |
         |            |
         R2 = 10kOmh  5.1v Zener diode to protect arduino pin
         |            |
         |            |
—————————————————————————— GND negative battery and arduino

Best Answer

to Q2. To save power, before you switch off something using transistors. Do these two first 1. write proper code to save power eg use very low cpu clock, make mcu sleep etc 2. choose low quiescent current LDO because a cheap L7805 has 2-3mA quiescent current.

Related Topic