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Project Notes

#167 VoltageSensorModule

Test a 25V voltage sensor module


This is a quick test of a 25V voltage sensor I picked up recently.


The circuit simply measures a variable voltage (manually controlled wiper on a pot) and displays the result on a 5110 LCD.

Module Specifications

  • Voltage input range : 0 - 25V DC
  • Voltage detection range : 0.02445 - 25V DC
  • Voltage analog resolution : 0.00489 V

Given the 25V range and taking a reading through the analog point (0-1023), then the actual voltage will equal the analog input / 1023 * 25.

Module Connections

Pin/Terminal Description
+ Sensor power 3.3/5V
- Sensor ground
s Sensor output
VCC Input positive DC
GND Input ground

Module Construction

Well taking a closer examination, there’s nothing much too it. As you might expect, it turns out to be nothing more than a voltage divider.

The sensor power pin is bogative - it’s not connected to anything. The module is not isolated - the input ground is common with the sensor ground.

The input voltage is applied across two resistors in series, with the sensor output tapped at the midpoint. The resistors are 0805 surface mount “precision” (4-digit code) resistors of values:

  • 3002 (30kΩ)
  • 7501 (7.5kΩ)

Hence the sensor output will read as 7.5/37.5 or 20% of the input voltage. Hence the 25V maximum voltage rating on the unit, since 20% is 5V, the input limit for a 5V Arduino.

5110 LCD SPI Configuration

The u8glib takes advantage of hardware SPI, which means pin connections are dictated for at least MOSI and SCK.

Here’s the mapping from the terminology used by my particular 5110 module and pins on an Arduino Uno.

Pin Usage Arduino Uno Pin
RST reset 8
CE/SCE chip enable 10 SPI SS
DC address line 0 9
DIN data in 11 SPI MOSI
CLK clock 13 SPI SCK
VCC power  
BL Backlight on when GND  
GND Ground  



The Schematic

The Build

Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.