Pet Monitor for RVs and Trailers (Saves Dogs From Heat!)

This is a monitoring device that keeps your dogs safe while camping in an RV or travel trailer.

We all know not to leave a dog in a hot car. But your RV or travel trailer can be just as dangerous. If it has an air conditioner, you can keep the interior cool and your dog comfortable. But what if your generator runs out of gas or your AC malfunctions? The result could be tragic if that happens while you're away on a hike or grocery shopping trip.

I built this device to prevent that. If you've heard of Waggle, it is basically like that (but cheaper). It monitors the temperature and humidity, snaps photos, and sends you an alert if conditions get too hot. All data goes over cellular through Hologram, which automatically switches networks, so it is reliable. That's also cheap, so it should only cost a few dollars a month to run.

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I created the first version of this device in just a few days for a camping trip my wife and I took from Arizona up to Yellowstone, and back. We have a Scamp fifth wheel travel trailer and wanted to ensure our dogs would be safe.

To get it done in such a short amount of time, I used Embedder. That is an AI created specifically for embedded development and it worked great. I recommend you check out Embedder if you do anything with electronics hardware!

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GitHub repository with all files is here:

https://github.com/theserialhobbyist/PetMonitor

Supplies

Electronics:

• Raspberry Pi Zero W 2
• Waveshare SIM7600G-H 4G HAT
• Hologram SIM Card
• BME280 Sensor Module
• IMX219 Arducam V2
• Micro USB power supply (cable or 12V-to-5V converter)

Fasteners:

• M3 heat-set threaded inserts
• M2 heat-set threaded inserts
• M3 screw assortment
• M2 screw assortment
• Standoff assortment

Enclosure:

• Base (3D-printed or CNC-milled)
• Cover (3D-printed)

Step 1: Order Hologram SIM Card

This device relies entirely on cellular connectivity. You can use something else, but I highly recommend Hologram. It is affordable and automatically switches between networks, for reliability and performance.

Running this monitor requires very little data (especially if you turn off photo uploads), so the Hologram service doesn't cost much at all.

Just sign up on the Hologram website to order a Hologram Hyper eUICC IoT SIM card. For me, it was only $3 + shipping.

Step 2: Prepare Enclosure

While you're waiting for your parts to arrive, you can go ahead and make the device's enclosure.

I designed the cover to be 3D-printed on an FFF 3D printer. It accepts heat-set threaded inserts, so resin printing isn't suitable. I recommend you print it in ASA, ABS, or something else that can hold up to heat. Supports aren't necessary.

Use a dedicated tool or a soldering iron to put M3 inserts into all of the holes, except the camera mount holes that take M2 inserts.

The base can be 3D-printed or CNC-milled. I milled mine out of brass on a Makera Z1 and I think that is the best choice. But if you don't have access to a mill, 3D printing is fine.

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Some background info on the design:

I used Autodesk Fusion CAD software to model the enclosure, as I usually do. But this time, I did that by first 3D-scanning the components using a Creality Sermoon P1. That let me bring meshes into Fusion, so I could model the enclosure around the components and get a perfect fit.

I want to refine that workflow a bit before I post a guide on how to do it, but I like the way this 3D scanning + Autodesk Fusion approach eliminates the need for cumbersome measurements taken with calipers.

Step 3: Understand the System

The system as two "sides."

First is everything that runs locally on the Raspberry Pi Zero W 2, which is about collecting data from the sensors/camera and interfacing with the SIM HAT to upload that data over the Hologram network.

Second is everything in the cloud, which receives the uploaded data, stores it, and gives the user an interface.

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Everything in the first group is built on Python, vibe-coded using Embedder.

Everything in the second group runs in a Google Firebase app (also vibe-coded with Embedder). It has a database and photo storage, plus a web interface where users can see the data, adjust some settings, view photos, and set the notification threshold.

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Notifications go through MQTT, because that requires very little data and is very reliable.

To get those notifications on your phone, you can use ntfy (free) or Pushover (one-time fee). Both have prioritization and emergency overrides of quiet/do not disturb modes.

I felt like that was very important, because you don't want to risk missing a notification when your dog is in danger.

In my testing on Android, ntfy worked just fine and provides notifications that are basically impossible to miss. From what I understand, Pushover might provide slightly better results on iOS and may be worth trying if you think ntfy isn't sufficient.

Step 4: Connect Components

The hardware is easy to connect.

The SIM HAT uses pogo pins, which is nice. All you have to do is attach the HAT to your Raspberry Pi using the provided standoffs and screws.

Then use the ribbon cable provided with the Arducam to connect it to the Raspberry Pi.

Finally, use some jumper wires to connect the BME280 sensor to the Raspberry Pi's GPIO pins:

| BME280 | Pi Pin | Notes |

|-----------|-----------------|-----------|

| VIN / VCC | Pin 1 (3.3V) | |

| GND | Pin 9 (GND) | |

| SDA | Pin 3 (GPIO 2) | I2C data |

| SCL | Pin 5 (GPIO 3) | I2C clock |

Address 0x76 = SDO tied to GND (set `i2c_addr` to `0x77` if SDO → VCC).

Step 5: Software Setup

Grab the files you need from GitHub:https://github.com/theserialhobbyist/PetMonitor

To make this a lot easier, I had Embedder create a setup script/installer thing.

It isn't quite as easy as just running an installer on Windows, but it helps to install the necessary dependencies and walk you through configuring everything.

It does that in two stages:

Stage 1 - on your development PC, handling the setup and deployment of the Firebase app.

Stage 2 - on the Raspberry Pi, handling the installation of the software packages and configuration.

The SETUP-GUIDE.txt document in the project files contains instructions on how to do all of that. The README.md file contains additional information that is particularly useful if you don't want to use the semi-automated installer/wizard (or if it doesn't work for some reason).

Step 6: Using the Web Interface

After following the setup instructions, you'll be able to access the Firebase web app through the browser on any device with internet. You should create Firebase credentials for the app for anyone who you want to have access.

The web app will contain photos of the interior of your RV/travel trailer, so privacy is important!

Then, in the web app, you will see the critical information and settings.

Displayed data includes:

• Status (online/offline)
• Current temperature
• Current humidity
• Pressure
• Time of last update (should update once per minute)
• Most recent photo
• Graph with a 24-hour history of temperature/humidity
• A gallery of recent photos

Available settings include:

• Whether or not to upload photos
• High temperature alert threshold
• Low temperature alert threshould
• High humidity alert threshold

There are many additional settings and configuration options that are not in the web app. Those are on the Raspberry Pi itself and you can tweak those during setup. That is, for example, where you enable/disable the notification service and enter the credentials for the service you choose.

Step 7: Assemble Device and Mount

Once you have everything setup and have verified that it works, you can finish assembly of the device.

Start by using M2 screws to attach the camera module to the cover. Then use M3 screws to attach the BME280 module to the cover.

Next, use the standoffs and their screws to attach the SIM HAT/Raspberry Pi to the base. From there, you can put the antenna threads through the cover, the washer/nut on the other side, and top it off with the antenna.

Finally, use M3 screws to join the base and cover. Everything should line up properly, so you can insert the micro USB cable for power.

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Mounting will depend on your RV/trailer. I designed the base with too long slots, so you can put through screws into a wood cabinet or something like that. You can also use strong double-sided tape.

You'll want to put it in a place with three qualities:

• Close to power (either a USB port or 12V power wires you can tap into)
• Good camera view, so you can see the interior where your dogs aren't
• Not too high or in direct sunlight (might throw off temperature readings)

Step 8: Go Camping!

Now you should be able to camp without stress!

Hologram switches networks automatically, so there is a very good chance you'll have coverage anywhere you camp. If coverage is poor or you want to limit data usage, you can turn off photo uploads. With those off, it uses very little data.

Before you rely on this for long periods of time, you should test it to make sure it works reliably.

And any time you're going to use it, keep in mind that both the monitor device and your own smartphone need service for alerts to go through. Because that requires little data and uses MQTT, the service can be poor and it will still work. But we're talking about the safety of your dog, so test it in each location to make sure you're getting updates!