Trigger over MQTT

This tutorial shows you how to remotely trigger your OV20i camera using simple MQTT messages. In just a few steps, you'll have a system that can capture and process images from anywhere on your network - no complex programming required!

What You'll Build: A simple remote trigger that lets you start camera inspections by sending a basic message over your network.

Estimated Time: 20-30 minutes

Skill Level: Beginner

Real Example: Imagine a button on an operator's tablet that instantly triggers the camera to inspect a part - that's exactly what we're building, but using MQTT messages instead of buttons.

Prerequisites

Before starting, make sure you have:

• OV20i camera connected and working
• A recipe set up and ready to use
• MQTT communication configured (see "MQTT Communication Setup" guide if needed)

note

Your camera trigger must be set to Manual in Imaging Setup - this tells the camera to wait for your remote commands instead of capturing automatically.

Why MQTT Triggering is Easy

The OV20i makes remote triggering simple:

• No coding required - just drag and connect a few nodes
• Works instantly - send a message, get results immediately
• Reliable messaging - MQTT ensures your commands reach the camera
• Any device can trigger - tablets, computers, PLCs, or sensors

Perfect for: Remote inspection control, automated production lines, or any situation where you need to trigger the camera from another location.

Step 1: Quick Camera Check

1.1 Set Camera to Manual Trigger

1. Go to your Recipe Editor
2. Click "Imaging Setup"
3. Find Trigger Mode and set it to "Manual"
4. Click Save

Why Manual? This tells the camera "wait for my command" instead of taking pictures automatically.

1.2 Find Your Recipe Number

1. Look at your browser address bar while in Recipe Editor
2. Find the number after /recipe/ (example: if URL shows /recipe/10, your recipe number is 10)
3. Write this number down - you'll need it in a few minutes

Step 2: Open the Flow Builder

2.1 Get to Node-RED

1. In your Recipe Editor, click "IO Block"
2. Click "Configure IO"

2.2 Start Fresh

If you see other nodes on the canvas, that's fine - we'll just add our new trigger flow alongside them.

Let’s begin!

Step 3: The Simple Secret to MQTT Triggering

Here's all you need to know: The camera needs 2 quick messages to take a picture remotely.

1. First message: "Hey camera, get ready for a remote command"
2. Second message: "Now take a picture!"

3.1 Drag These 5 Nodes onto Your Canvas

From the left panel, drag these onto the main area:

1. Inject (from Input section) - This will be your "trigger button"
2. Change (from Function section) - For message 1
3. Delay (from Function section) - Tiny pause between messages
4. Change (from Function section) - For message 2
5. MQTT Out (from Network section) - Sends messages to camera

Step 4: Configure Your Nodes

4.1 Set Up Your Trigger Button

1. Double-click the Inject node
2. Change the name to "Remote Trigger"
3. Click "Done"

4.2 Set Up Message 1 (Get Ready Command)

1. Double-click the first Change node
2. Change name to "Get Ready"
3. Click "Add" and select "SET"
4. Set msg.topic to stream_mode/set
5. Click "Add" again and select "SET"
6. Set msg.payload to HMI_MODE
7. Click "Done"

What this does: Tells the camera "get ready for a remote command."

4.3 Add a Small Delay

1. Double-click the Delay node
2. Set delay to 10 milliseconds
3. Click "Done"

Why? Just gives the camera a split second to get ready.

4.4 Set Up Message 2 (Take Picture Command)

1. Double-click the second Change node
2. Change name to "Take Picture"
3. Click "Add" and select "SET"
4. Set msg.topic to hmi/[YOUR_RECIPE_NUMBER]/capture_mode
5. Replace [YOUR_RECIPE_NUMBER] with your actual number (like hmi/10/capture_mode)
6. Click "Add" again and select "SET"
7. Set msg.payload to single
8. Click "Done"

What this does: Tells the camera "take one picture now!"

4.5 Set Up the Message Sender

1. Double-click the MQTT Out node
2. Select your MQTT broker (should already be configured)
3. Change name to "Send to Camera"
4. Click "Done"

Step 5: Connect Everything Together

This is the fun part! Now we connect your nodes to create the flow.

5.1 Make the Connections

Draw wires between nodes like this:

1. Remote Trigger → Get Ready → Send to Camera
2. Remote Trigger → Delay → Take Picture → Send to Camera

Visual guide:

Remote Trigger ──→ Get Ready ──→ Send to Camera
      │
      └──→ Delay ──→ Take Picture ──→ Send to Camera

5.2 How to Connect Nodes

1. Click and drag from the little square on the right side of a node
2. Drop the wire onto the left side of the next node
3. You'll see a gray line connecting them

Step 6: Test Your Remote Trigger

6.1 Activate Your Flow

1. Click the red "Deploy" button in the top-right corner
2. You should see "Successfully deployed" message

6.2 Try It Out

1. Place a part in front of your camera (for testing)
2. Click the button on your "Remote Trigger" node
3. Watch your camera take a picture!

Success signs:

• Camera LED flashes briefly
• You hear the inspection processing
• New image appears in your Library

6.3 Check Your Results

Go to your Library page - you should see a new image with a recent timestamp. Click on it to see the inspection results!

If it worked: Congratulations! You just remotely triggered your camera.

If not: Check the troubleshooting section below.

Step 7: Use It from Other Devices (Optional)

Want to trigger from your phone, tablet, or another computer? Here's how:

7.1 From Any MQTT App

Download any MQTT app and connect to your camera's IP address on port 1883, then:

1. Send first message:
   • Topic: stream_mode/set
   • Message: HMI_MODE
2. Wait a moment, then send second message:
   • Topic: hmi/[YOUR_RECIPE_NUMBER]/capture_mode
   • Message: single

7.2 From Command Line

On Windows/Mac/Linux:

# First message
mosquitto_pub -h [CAMERA_IP] -t "stream_mode/set" -m "HMI_MODE"

# Second message (replace 10 with your recipe number)
mosquitto_pub -h [CAMERA_IP] -t "hmi/10/capture_mode" -m "single"

That's it! Your camera will take a picture from anywhere on your network.

Step 8: Validation and Testing

8.1 End-to-End Testing

Complete workflow validation:

Test	Action	Expected Result	Status
Manual trigger	Click inject button	Image captured and processed	☐
HMI mode activation	Check camera status	Camera switches to HMI mode	☐
Inspection execution	Verify processing	Debug shows inspection results	☐
External trigger	Send MQTT command	Remote triggering works	☐

8.2 Performance Validation

Monitor these metrics:

• Trigger response time: From MQTT message to image capture
• Processing duration: Time to complete inspection
• Result delivery: Debug output timing
• System reliability: Consistent triggering over multiple tests

8.3 Production Readiness

Before deploying to production:

1. Test with actual parts and inspection conditions
2. Verify integration with your external systems
3. Confirm network reliability for MQTT communication
4. Document trigger topics and message formats

Step 9: Quick Troubleshooting

Not working? Here are the most common fixes:

9.1 Camera Doesn't Take Pictures

Problem	Quick Fix
Nothing happens when I click trigger	Check that your recipe number is correct in the "Take Picture" node
Camera takes picture but no inspection	Make sure your recipe is Active and has a trained model
Trigger works sometimes	Verify trigger is set to Manual in Imaging Setup

9.2 MQTT Issues

Problem	Quick Fix
Red dots on MQTT nodes	Check MQTT broker connection in your setup
Deploy button is grayed out	Click anywhere on the canvas first, then try Deploy
Nodes won't connect	Make sure you're dragging from the little square on the right side

note

Still stuck? Double-check that MQTT communication is set up correctly (see the MQTT Communication Setup guide).

You Did It! 🎉

Congratulations! You now have remote control of your OV20i camera. With just a few clicks, you built a system that can:

• Trigger inspections from anywhere on your network
• Work with phones, tablets, computers - anything that can send MQTT messages
• Integrate with other systems like PLCs, sensors, or custom applications
• Scale to multiple cameras by using different recipe numbers

What's Next?

Now that you have the basics working, you can:

Easy Next Steps

• Test from different devices using MQTT apps
• Create multiple triggers for different recipes
• Add this to your production workflow

Advanced Ideas

• Connect to PLCs for automated production lines
• Build custom apps that trigger multiple cameras
• Add result forwarding to send inspection data elsewhere
• Create operator dashboards with trigger buttons

Real-World Examples

Here's how others use MQTT triggering:

• Quality Control Stations: Operators scan a barcode, system triggers camera inspection
• Conveyor Lines: Sensor detects part, automatically triggers inspection
• Manual Inspection: Tablet with simple "Inspect" button for operators
• Production Monitoring: Central system coordinates multiple cameras

The possibilities are endless - and it all starts with the simple system you just built!

🔗 See Also

• MQTT Communication Setup
• Set Digital Output Logic
• Connect to PLC (Ethernet/IP, PROFINET)
• Node-RED Basics
• Overview Node-RED Custom Blocks
• Camera to PLC Communication Fails