Pressure regulated Water Pump

Custom Build with a PTO driven water pump electrically powered and pressure regulated.

Custom Build with a PTO driven water pump electrically powered and pressure regulated.
This project transforms a PTO (Power Take-Off) pump, intended for tractors, into an electrically driven system. The system features a pressure and flow sensor, with a microcontroller controlling a bypass valve and a 4 kW electric motor.

Reasons for this project

Why choose PTO Pump?

  • Enhanced Performance: Significantly higher pressure (typical 25 bar vs 5 bar) and flow capabilities compared to commonly available pump systems
  • Versatility: The same pump can still be used with a tractor when needed

Why automate it?

  • Noise Reduction: Minimize noise level by operating the pump only as fast as necessary
  • Energy Efficiency: Optimize power consumption by reducing motor speed and pressure
  • Flexible Control: Microcontroller-driven system allows for easy integration of additional features (e.g. timeouts, remote-control)

image High flow, medium pressure application



  • Belt drive
    • Pulley motor: 2x13mm, d=100mm
    • Pulley PTO-shaft: 2x13mm, d=250mm
    • 2 x 13mm v-belt
  • Expansion tank: 8 Liter
  • Bypass valve: 3/4”
  • Pressure relief valve: 10 bar
  • PTO Shaft: 1 3/8” (34.9 mm)
  • Bearings: 2x 35 mm roller bearings with clamping sleeve
  • Various fittings, valves, couplings…

image Main pipe assembly with flow sensor, bypass and pressure relief valve


  • Name: ML 20
  • Power: 4 kW
  • Rotational speed:
    • Max: 700 rpm
    • Rated: 540 rpm
  • Connection: 1 3/8”, 6 Tooth PTO shaft
  • Max. Pressure: 25 bar
  • Flow rate:
    • Low pressure: 180 l/min
    • High pressure: 70 l/min

image PTO-Pump with cover removed


  • Rated power: 4 kW
  • Rotation speed: 1415 rpm
  • Voltage: 380 V
  • Frequency: 50 Hz
  • Type: Three phase asynchronous motor
  • Attachment: Star-delta cam switch
  • Previous application: Powering a stationary thresher

image Motor mount is being positioned on the frame


  • Controller: Custom pcb with ESP-32 microcontroller
  • Switching power supply: 12 V, 2 A
  • VFD: 7.5 kW variable frequency drive
  • Servo motor: DS51150-12V 150 kg
  • Pressure sensor: Analog 5 V, 0-34.5 bar (500 psi)
  • Flow sensor: Size 2”, 5-24 V, 10-200 L/min, 12 Pulses per Liter

image Open control cabinet with power supply, custom pcb, VFD and Display


  • Regulation
    • Speed Control: Automatically adjusts motor speed to match the water demand using the VFD
    • Pressure Regulation: Maintains consistent pressure output using PID control manipulating the bypass valve with a servo motor
  • User Interface
    • Hardware Interface:
      • Start/stop and set target pressure using buttons
      • View sensor data on 7 segment display
    • Web Interface:
      • Control pump remotely
      • View data history
  • Smart Control
    • Auto Power Down: Enters power-saving mode during inactivity
    • Dynamic pressure: Reduces Pressure when no water is used

image First test with servo controlling the bypass valve

Electrical overview

All electrical aspects were planned in the following document:

Complete Document


The firmware for the esp32 on the custom pcb was created using the following components:

  • Programming Language: C++
  • Development Framework: ESP-IDF
  • Flowchart Design:
  • Version Control: Git

The repository with the source code and all relevant documents is available on GitHub


First test (motor, frame)

2018.05.11 - First test of the welded frame and old motor:

Test hardware UI

2024.05.21 - Set target pressure and start the pump using potentiometer and buttons:

Start with phone

2024.05.21 - Set target pressure, start and check data using the web interface:

Test valve, motor control

2024.05.21 - Motor speed and valve position are automatically adjusted to achieve the desired pressure while varying the water flow: