Here is a useful circuit for Arduino lovers and experimenters. It is a simple digital voltmeter, which can safely measure input dc voltages in 0 to 30V range. The Arduino board can be powered from a standard 9V battery pack, as usual.
As you may well know, Arduino’s analog inputs can be used to measure DC voltage between 0 and 5V (when using the standard 5V analog reference voltage) and this range can be increased by using two resistors to create a voltage divider. The voltage divider decreases the voltage being measured to within the range of the Arduino analog inputs. Code in the Arduino sketch is then used to compute the actual voltage being measured.
The
analog sensor on the Arduino board senses the voltage on the analog pin and converts it into a digital format that can be processed by the microcontroller. Here, we are feeding the input voltage to the analog pin (A0) using a simple voltage divider circuit comprising resistors R1 (100K) and R2 (10K). With the values used in the voltage divider it is possible to feed voltage from 0V to 55V into the Arduino board. The junction on the voltage divider network connected to the the Arduino analog pin is equivalent to the input voltage divided by 11, so 55V ÷ 11 = 5V. In other words, when measuring 55V, the Arduino analog pin will be at its maximum voltage of 5V. So, in practice, it is better to label this voltmeter as “0-30V DVM” to add a safety margin!
Arduino Code: Click Here
