Wiring & Connections

The OWL’s relay outputs can switch any 12V device, making it versatile for spot spraying, demonstrations, educational setups, and custom applications.

What Can Be Connected

The OWL provides 4 relay channels, each capable of switching 12V DC devices up to 10A. Any device that operates on 12V can be controlled.

Spray Applications

Device

Use Case

Solenoid valves

Spot spraying herbicide, liquid fertiliser

Electric ball valves

Higher flow applications

Diaphragm pumps

On-demand spraying

Demonstration & Educational

For testing, demonstrations, or educational purposes, you can connect visual indicators instead of (or alongside) spray equipment:

Device

Use Case

12V LED strips

Visual indication of detection zones

12V indicator lights

Dashboard-style detection feedback

12V buzzers

Audio feedback for detections

12V light bulbs

High-visibility demonstration

Tip

Educational setups using lights are excellent for:

  • Training operators before field deployment

  • Demonstrating detection algorithms at workshops

  • Testing and calibrating without using spray chemicals

  • Indoor demonstrations at agricultural shows

Other Applications

Device

Use Case

Electric actuators

Targeted tillage, mechanical weeding

Ignition modules

Spot flaming systems

12V motors

Custom mechanical systems

Relay modules

Switching higher voltage/current devices

Relay Specifications

Parameter

Value

Number of channels

4

Switching voltage

12V DC

Maximum current per channel

10A

Actuation type

Normally Open (NO)

Control

GPIO-driven via Raspberry Pi

Wiring Solenoids

Pin Mapping

Each relay output corresponds to a coloured wire on the Bulgin connector:

Relay

GPIO Pin

Wire Colour

Bulgin Pin

Relay 0

GPIO 13

Blue

Pin 1

Relay 1

GPIO 15

Green

Pin 2

Relay 2

GPIO 16

Orange

Pin 3

Relay 3

GPIO 18

White

Pin 4

12V Power

-

Red

Pin 5

Ground

-

Black

Pin 6

Basic Wiring

  1. GND wire of your device connects to the ground pin on the Bulgin plug (same wire used for GND from 12V power source)

  2. Positive wire of your device connects to one of the relay outputs (Blue, Green, Orange, or White)

Warning

The relay switches the ground side of the circuit. Your 12V device should have its positive terminal connected directly to the 12V supply, and the negative terminal connected through the relay.

Wiring Diagram

Solenoid Wiring Diagram

Six-Way Harness

The easiest wiring method is to create a six-way harness:

  • One end connects to the Bulgin plug

  • One wire connects to source power GND (shared ground)

  • Four remaining wires connect to your devices (solenoids, lights, etc.)

Bulgin plug

Ground wiring harness

Bulgin plug

Ground harness

Example: Indicator Light Setup

For demonstrations or testing, wire 12V LED indicators to each relay:

Parts needed:

  • 4x 12V LED indicator lights (panel mount)

  • Wire (appropriate gauge for your LEDs)

  • Connectors or solder

Wiring:

  1. Connect all LED positive terminals to 12V supply

  2. Connect each LED negative terminal to a separate relay output:

    • LED 1 → Blue wire (Relay 0)

    • LED 2 → Green wire (Relay 1)

    • LED 3 → Orange wire (Relay 2)

    • LED 4 → White wire (Relay 3)

When OWL detects vegetation in a zone, the corresponding LED illuminates.

Configuration

Relay Timing

Adjust how long relays stay activated after detection:

[System]
actuation_duration = 0.15
delay = 0
relay_num = 4

Parameter

Default

Description

actuation_duration

0.15s

How long relay stays ON after detection

delay

0s

Delay between detection and relay activation

relay_num

4

Number of relay channels to use

Detection Zones

Each relay corresponds to a horizontal zone in the camera’s field of view. When vegetation is detected in a zone, the corresponding relay activates.

Camera View:
┌─────────┬─────────┬─────────┬─────────┐
│ Zone 0  │ Zone 1  │ Zone 2  │ Zone 3  │
│ Relay 0 │ Relay 1 │ Relay 2 │ Relay 3 │
│ (Blue)  │ (Green) │ (Orange)│ (White) │
└─────────┴─────────┴─────────┴─────────┘

Safety Considerations

Warning

Electrical Safety

  • Ensure all connections are secure and insulated

  • Use appropriate wire gauge for your current requirements

  • Include inline fuses for protection

  • Keep wiring away from moving parts and heat sources

Warning

Spray Equipment

  • Follow all chemical handling guidelines

  • Ensure proper PPE when working with herbicides

  • Test systems with water before using chemicals

  • Verify solenoid ratings match your operating pressure

Next Steps