Arrival sensor for car

I just finished re-doing my garage door. I moved from MYQ to local controlled garage door like many of us here. I am pretty happy with it. I used to have a couple ST Arrival sensor that I put in my car and use to automatically open the garage door when my cars arrived home. These has not been working well with MYQ. Yet, after the local controlled GD, this automation is very useful again.

Now, I have a different problem. We just got a new car about a year or so ago. The ST arrival sensor seems not available or is very hard to find one for sale in USA.

I could use Bluetooth beacon for presence. But, I am a little concern because Bluetooth beacon does not require authentication. Anyone can copy the beacon packets and reply it over to open the garage door.

I have been making my Zigbee Sensors on another projects. I thought I could make an arrival sensor out of it. I am also looking for opportunity to make some improvement.

First, I want to address probably the biggest issue with ST arrival sensor. It has a very weak battery. It is well documented that many of us modified these sensors with bigger external battery. I am going with a different route for mine. I will use a re-chargeable battery. The battery will be re-charged during the drive. It will have enough charge for typical daily driven car.

Second, I will use high powered Zigbee module. I am hopping to get better connection compared to the ST sensors. I am also planning to use a Zigbee module that can use external antenna.

Here are is what mine will look like in the hub.

Here are a few things that are unique to what I make.

  1. We will know whether the car is running by looking at whether the sensor is charged. I can configure different timeout based whether the car is running or stopped. This will reduce the false positive/negative of the presence status. When the car is leaving on its own power, a more aggressive timeout can be used. This will allow the "not present" detection much faster. When the car is not running, much more relax timeout can be used to be more robust in a non ideal Zigbee mesh.

  2. I added an vibration sensor and microwave radar sensor. They will show up as motion and shock attributes.

  3. We will have temperature monitoring for the car. Improvement 2 and 3 are intended to help securing the car when it is present at the house.

BTW, the firmware will also be fully compatible with Hubitat built in Arrival sensor. But, you will not get the extra information.

Here is my prototype board. Again, it is very rough and for my testing only. Eventually, I will have a specialized board made for it. This should be plugged in to cigarette lighter with 5V dc converter.

I will have a few PCB boards made specifically for the arrival sensor. It is not easy to source parts these days. When I am ready, I am happy to share the sensor for those who are interested. If you have other idea that you like to have on the sensor, please feel free to let me know. If I can accommodate it, I will be happy to do so.



I want several if the R&D is not to expensive.

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Hello Iman,

I too am interested; for now, I'm using a SmartThings arrival sensor powered by a couple AA batteries.

Will it be possible for you to design a case for this product?

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@tmcdonald, I will get some idea for the cost in the next couple of weeks. Yes, we will be looking for parts that would be reasonable.

@aaiyar, Thanks for the feedback. I will try to design the PCB to be case friendly. I do want to have a case for it. But, it almost likely would not be a custom case. We may have to live with pre-made box. What this mean is that, it won't be perfect (or perhaps look nice).


Have a look at the cases for the Raspberry Pi: Raspberry Pi Cases | The Pi Hut

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Amazing as always @iharyadi please let us know when you have something available.

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I just got these. Removed the space has two batteries and soldeed the sensors.inside and velcroed to back deck.

Thanks @UKMedia for the cases ideas. I will look at them and see if I can match one with the PCB that I am making.

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Love this idea! Been playing with beam sensors to check for garage occupancy, but I’d prefer true car presence. And monitoring whether car is running is a great touch!

I’m not sure what you mean by this. Will the device work to report when the car is and isn’t present? When I’ve played with xbee’s in the past, the trick was always how fast the hub would rediscover the car presence sensor and report it as present. Needs to be pretty quick to trigger a garage door opener.

One related use-case I’ve not found a way to solve: putting an open/close sensor on the car door to trigger garage door to open just prior to leaving the house.

Nice idea!

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Yes, it will detect the car presence. Using the Hubitat built-in driver will only show presence. You will not be able to know whether the car is powered.

This is really cool. I would do this only when you have the car inside a garage. A couple of my car is actually is parked on my drive way. I would not want to have the garage door opened when I open my car door. Currently, my sensor is not precise enough to tell whether my car is inside my garage. I suppose we can looked at UWB sensors. I heard that UWB sensor can give centimeter precisions of your position. With this, you can tell whether the car is in a garage or outside the garage. But, the UWB is still costly.

BTW, my current microwave radar worked like a contact sensor. My car looked like a faraday cage. The microwave sensor does not detect any human outside the car when you have closed windows and doors. But, as soon as I open my door, it will detect me. It acts just like a contact sensor. I am ordering a different microwave sensor as we speak to learn about the different type of these type of sensors. My initial goal is actually to create 1 to 2 feet shield around the car. As people approach the car, I would be able to detect it.

I did something similar using a Xbee3 pro and programed the micro python code for 1 second transmitting. Just plug it into the cars usb outlet. When the car starts it powers on the Xbee3.
Then create a rule that automatically opens the garage door on arrival.
Works great for opening the garage when coming home as well.
Add extra range if you put a second Xbee3 pro setup as a router inside the garage.

Only issue is if parking in the driveway and you start the car it will open the garage door.

For just detecting if the car is parked at home I use a second old smartthings arrival sensor with the battery mod in a case but I also added a rechargeable circuit (I took from an old Xbox controller) with usb cable and rechargeable batteries to plug into another usb car outlet to charge the rechargeable batteries when driving.


I read briefly about using Xbee3 pro & the python. I decided not to go this route. I was not sure whether you would need to add battery. I am also not quite sure whether it would run as Sleepy End device or Repeater.

Since I am going DIY anyway, I thought that I would make my own. Here is just an idea of early PCB design for what I am thinking. I may want to resize the board to fit a pre-made box once I found one. The USB and SMA connector may also be gone if a suitable box is found.

you can program the Xbee3 pro as an end device or a router. For presence I set to end device and 1 second transmitting and they work great.

How much transmitting power is you DIY device transmitting or what is the range?
Xbee3 pro is Transmit power +19dBM approx * 300ft (indoor) to 2mile (outdoor) range.

Would be great if you could add a rechargeable circuit to use rechargeable batteries and be able to plug into a usb and recharge them while driving.
Likely a lot of demand since the smartthings arrival sensor are no longer made.

PS still running your original Homemade Temperature, Humidity, Pressure and Light sensor
works great!

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It is good to know.

Yes, it is pretty similar power +20dBM ish. I am going to use the module with external antenna this time around. It seems our car block 2.4Ghz signal really good. It is not just our house.

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BTW, I would like to confirm that It has recharge-able battery support. Even the prototype has it already using the Environment Sensors boards.

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A rechargeable circuit for rechargeable batteries I would definitely buy a few.
One thing the smartthings arrival sensor was missing.

The rechargeable circuit from the Xbox controller works great but I only had one old dead controller.
I tried some rechargeable circuit boards from china but they didn't work and just never got back to trying to source a working circuit.

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Understand, but will you release a custom driver that includes presence and on/off?

Yes definitely on when the car is inside the garage. I’m not sure, but Will the faraday concept work for my use case because I’m trying to get the garage door to open when I’m getting into the car to depart, rather than exit the car after arrival.

Also, you can solve for car presence in the garage by using cheap NO/NC photoelectric beams. Cheap and easy. Happy to share more of there’s interest.

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