Cheap car presence & position detection in Home Assistant with ESPHome

Wouldn’t it be nice to instantly see if you forgot your car outside when going to bed or check if there is space in the garage to fit your car? Well in my case having a garage where 2 cars go one behind another, brings an issue since I would like to know if there is room to fit the car of maybe I have to leave the car outside while arriving home for cheap?

That is how my journey with this project began.
Inspired by the salt-level sensor project I have on another post, I used the HC-SR04 Ultrasonic Distance Sensor. Actually 4 of them, combined with a Wemos D1 mini running ESPHome.

Materials List

So what do you actually need?
Depending on your garage configuration your needs may vary . In this case let’s focus first on my configuration. I used one Wemos D1 mini, 4 HC-SR04 and 6 meters of cat5 cable

Main Components

Additionally you will need

• Some wires to connect the sensor to the D1 mini. I preferred using a cat5 cable and splicing it into it but that is up to you. You can also use a 4 wire cable for every sensor.
• A 5V power supply for the D1 mini. (A mini usb phone charger is more than enough)
• a mini USB cable (for flashing)

Additional tools and hardware

For this project soldering is required, here is a list of some additional tools you could find handy

(optional) shrink-tube

Shrink tubes aren’t required but they will help you to avoid short-circuits and will make your project look a lot tidier … bonus: they will hide soldering defects.

Depending where you will place your D1 a case might come in handy. I’ve hidden mine in the garage motor. If you would like to place it somewhere else this is the way to make it look tidy

Software

I’ve used the following software to complete the project:

• Home Assistant
• ESPHome
• ESPHome Flasher
• Influxdb (add-on)
• Grafana (add-on)

Since this is a Home Assistant based site you would come to the obvious conclusion that Home Assistant is required. ESPHome is my firmware to run on my boards, you can also use tasmota but I have not tried that as of yet.

Alright then, let’s get started

Can the D1 mini cope with 4 sensors ?

That was the question I asked myself. There was only one way to know for sure: test it.
I pulled out a breadboard, some Dupont wires and quickly slapped it all together to get to this beauty :

I connected each sensor one by one and added them to the esophome.yaml until they were all connected and checked they were reporting the correct values. So let’s get serious now

Flashing the firmware on the D1 mini

As mentioned above I used ESPhome. If you do not know ESPHome and have no clue what I’m talking about, well, head up to their website. They have it well explained. So please do take the time to read the guide.

• Getting Started with ESPHome (for Hass.io users)
  Getting Started with ESPHome (when not on Hass.io)

Preparing the firmware

This part will depend a lot of how you are going to setup and install your sensors. This example is based on my setup and you can modify it as you see fit.

Things to take into account:

The sensors are supposed to be precise up to 4 meters. However I’ve found their best working distance is from 0 to 200 cm. Any further and you might get false values. I for my hand can work with these false values and will explain that a little bit further.

Since I wanted to measure the car’s height I had to subtract the measured value to the overall distance from the floor to the distance

Let’s assume we have a ceiling height of 250 cm and we would like to know the height of the car:

height of the car = 250cm – x

So if h2 would be 100 cm we would get :

h = 250cm – 100cm
h = 150cm

In ESPHome there are so called filters that allow you to modify the calculated value before it gets sent to Home Assistant

The actual code

Create a file called car_position_sensor.yaml; for Hass.io users, create the file in the /config/esphomefolder, so you end up with the file: /config/esphome/car_position_sensor.yaml.

Next, add the following contents to the file:

The above snippet shows an ESPHome project file in the YAML format.

The pins D0 to D8 may vary depending on how you will solder your sensors.
You will also have to measure the distance between the sensor and the floor for each sensor in order to input the correct value for their correct lambda calculations.

On lines 9 & 10, make sure to set your WiFi details or else you might end up with failure. Save the file and open up the ESPHome web interface; The Car_position_sensor project should appear!

Uploading the firmware to the D1 mini

In order to upload the firmware to the D1 mini, we will make use of the usb port provided on the device.

Plug the USB cable into your PC and the mini USB into the D1 mini. Now start the ESPHome flasher tool. Select the available serial port, and load the car_position_sensor.bin file by clicking the “Browse” button. Start the flash procedure by clicking the “Flash ESP” button. The console shows you the progress and tells you when it finishes.

Wiring up the D1 mini and the sensors

Next we will start wiring up the devices. I have them separated 1.80 m of each other. That is enough so that a car is always below 2 sensors at least and in my case that is required (I’ll explain that later).

Since I used a cat 5 cable I had 3 sensors settled. I used the Red-Redwhite wire pair for VCC and GND and then used another wire pair for each sensor. The front one is so close that I just connected it directly with a 4-wire cable.

The most important part, and where patience is required, is the soldering. Please verify multiple times that there is no short-circuit on one of your sensors or your D1 mini will die. The pictures below show what happens if you are sloppy. Anyway, let’s avoid calling it a failure since I have learned my lesson.

Soldering done? Good let’s carry on

Now that you have soldered all the sensors and have verified there is no short-circuit, it’s time to test if all is working right and you have wired the pin-outs correctly.

Connect your D1 mini to a power source and verify it is online in ESPHome.

If the sensor isn’t online, verify your config and try flashing it again. If it should still fail please revert to the “useful information” section

Installing the sensors in the garage

So now that the sensor is working in ESPHome, it is time to install it in your garage. Now this is totally up to you, however since i wanted to avoid false positives, and identify what car is turned in which direction. This meant, I have to have the car under 2 sensors at all time at least. Try to keep them centered as well

Integrating the sensor in Home Assistant

Now this is really easy thank to the efforts the Home Assistant dev team has done. In Home Assistant, go to: Configuration > Integrations > the sensor should appear at the top. Follow the steps below to integrate it in Home Assistant

Prepping for lovelace-UI

In this section we will look into the data provide by the sensors try to understand it and act accordingly.

Getting the sensors in grafana will help us visualize what these values will look like

Installing InfluxDB / Grafana and reading data

In order to get nice graphs in grafana you need to have the data stored in a database. Here is where InfluxDB comes into play. We will get the values sent from ESPHome to Home Assistant , send them in InfluxDb and then pull them from in grafana.

I won’t explain that part since there is a nice video by frenck on how to do it. He’s doing it in a “speedrun” so you might consider slowing the video down by 0.75 or even 0.5. Grab some popcorn, sit back, relax and enjoy this nice little video.