# 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](https://user-images.githubusercontent.com/40649348/156698481-3d4fec4e-567a-4a18-b72e-b26d35c8d1c7.png)

---

## 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](https://media.github.sydney.edu.au/user/5402/files/7f753380-d03a-11eb-8d9b-658db73d3408) | ![Ground harness](https://media.github.sydney.edu.au/user/5402/files/7e440680-d03a-11eb-9af1-67132f4cc36f) |

---

## 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:

```ini
[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
```

---

## Recommended Solenoids

For spot spraying applications:

| Component | Recommendation |
|-----------|----------------|
| Solenoid valves | Goyen 3QH/3662 with Teejet body |
| Spray tips | Teejet TP4003E-SS (40°, flat fan, stainless steel) |
| Strainer | TeeJet 50 mesh |

See [Use Cases](../use-cases/index.md) for complete spray system specifications.

---

## Next Steps

- [Use Cases](../use-cases/index.md) - Complete application examples
- [Operation Guide](../operation/index.md) - Detection algorithms and performance
- [Configuration](../../software/configuration/index.md) - Full parameter reference