Building a Smarter Garage Door: Precision Positioning and Obstruction Detection

Going beyond open and closed with magnetic encoders, intelligent sensing, and HomeSeer integration.

Most garage door automation systems are surprisingly limited. They can tell you whether the door is open or closed, and some can report when it's moving. A few provide an approximate position.

But what if you want to know that your garage door is exactly 37% open? Or open it just enough for ventilation, without leaving it wide open? Or detect something obstructing the doorway before allowing the door to move?

Those questions started me down another of my little engineering rabbit holes.

I've been looking into building a garage door monitoring and control system that goes well beyond what conventional smart garage door controllers offer. Naturally, I'd like to integrate it with HomeSeer, but the interesting part is how to measure the door's position accurately and monitor the opening safely.

This is still a design-and-investigation project, and I'm sharing some of the thinking behind it.

The problem with open and closed

My garage door uses an older Genie screw-drive opener. It's dependable, but it wasn't designed with modern home automation in mind.

Most smart garage door solutions use one or two sensors, typically magnetic contacts or tilt sensors. These work reasonably well for answering basic questions:

Is the door fully closed?
Is it fully open?
Has something changed?

Unfortunately, they can't tell you much about what happens between those positions.

I'd like considerably more information.

For example, I might want to open the door 10% for ventilation, 30% for another purpose, or stop at any other position I choose.

I'd also like HomeSeer to know the door's actual position rather than simply assuming it reached the requested destination.

That distinction becomes important when something interrupts the door's movement.

Measuring position at the source

The first challenge is finding a reliable way to measure the door's movement.

I initially considered several approaches, including sensors that follow the opener's movement and an encoding strip that could report the door's position along its travel.

Those approaches are possible, but they introduce additional mounting and alignment challenges.

Then I started looking at the garage door's torsion shaft.

The shaft above the door rotates as the door opens and closes. By measuring that rotation, we can calculate how far the door has moved.

And unlike timing how long the opener has been running, we're measuring actual mechanical movement.

A magnetic rotary encoder

One promising solution is the AS5048A, a 14-bit magnetic rotary position sensor.

It uses a small magnet attached to a rotating shaft and a nearby stationary sensor. As the magnet rotates, the sensor measures its angular position.

There are several things I like about this approach:

No physical contact between the sensor and the rotating shaft.
No mechanical gears or wheels to wear out.
Very fine angular resolution.
A relatively inexpensive sensor.
Straightforward communication with a small microcontroller.

The encoder itself can distinguish 16,384 angular positions within a single revolution.

That's considerably finer than we need for a garage door, but it gives us plenty of resolution to work with.

The complication is that the torsion shaft makes multiple revolutions between fully closed and fully open. The sensor reports only its position within one revolution, so our controller needs to track revolutions and maintain a running position count.

It also needs a dependable way to establish its reference position, especially after a power interruption or if someone moves the door manually while the controller is off.

The current idea is to mount the magnet on the end of the approximately 3/4-inch torsion shaft, with the sensor mounted on a stationary bracket.

That would give us a compact, contactless measurement system without modifying the opener itself.

Of course, the torsion assembly is under considerable mechanical load, so we need to mount and align it without disturbing the spring hardware.

Turning rotation into a useful position

Once we can measure the shaft's movement, we can calibrate the system using the fully closed and fully open positions.

HomeSeer could then display something considerably more useful than a simple on/off state:

Garage Door: 37% Open

The calculated percentage wouldn't necessarily represent a perfectly linear relationship between shaft rotation and vertical door travel. The cable drums, door geometry, and changing movement of the door sections can affect that relationship.

For ordinary automation, a calibrated percentage may be sufficient. For more precise positioning, we could create a calibration table that relates shaft rotation to actual door height.

That opens the door, so to speak, to some interesting possibilities.

Instead of issuing only Open and Close commands, HomeSeer could request a particular position:

Open to 10% for ventilation.
Open to 50%.
Open completely.
Close the door.

And because we're monitoring the shaft, we should also be able to recognize when the door is moving, when it has stopped, and when its actual position doesn't match what we requested.

One important detail is that the encoder tells us where the door is, but it doesn't automatically let the existing Genie opener stop reliably at arbitrary positions. Achieving that will require additional control logic and testing.

Knowing when something is in the way

Position monitoring is only half of what I'd like to accomplish.

Conventional garage door safety sensors typically use an infrared beam near the bottom of the opening. If something interrupts that beam while the door is closing, the opener should stop or reverse.

That's an important safety feature, and I have no intention of replacing or bypassing it.

However, a single beam doesn't tell us what's happening throughout the rest of the doorway.

Imagine a vehicle, a ladder, or some other object extending into the opening above the existing beam. The original sensor might never detect it.

I'd like to monitor the entire opening, not just a narrow line near the floor.

An infrared light curtain

One option is a light curtain with multiple infrared beams at different heights.

Rather than checking only one location, the system would monitor a series of beams across the opening.

This could provide two useful pieces of information:

Whether something is obstructing the doorway.
Approximately where, vertically, the obstruction is located.

For example, HomeSeer might report:

Garage Opening: Obstructed

Obstruction Height: Approximately 24–36 inches

The idea is to use modulated infrared signals, potentially around 940 nm, rather than simple continuously illuminated infrared emitters.

Modulation and filtering should help distinguish our sensors from ambient light, which matters because the garage opening is exposed to direct Arizona sunlight.

Of course, we'd need to test sunlight rejection, alignment, sensor spacing, and reliable operation.

I'd also want the system to detect when a beam or sensor fails rather than incorrectly reporting the opening is clear.

What about LiDAR?

Another possibility I've been investigating is two-dimensional LiDAR.

Where a light curtain tells us which beams are interrupted, a suitable LiDAR sensor could potentially identify objects and their approximate locations within a scanned plane.

That could be useful if we wanted to know not only that something was in the opening, but also where it was located.

There are trade-offs, naturally.

LiDAR is more sophisticated, generally more expensive, and may introduce additional concerns about sunlight, reflective surfaces, object detection, and processing.

For now, I'm leaning toward a layered approach:

Use a light curtain for relatively straightforward obstruction monitoring, and consider LiDAR as an additional information source if it provides enough practical benefit.

Neither would replace the garage door opener's existing safety system. Any supplemental detection system would need to prevent unsafe automated commands without interfering with the opener's certified safety features.

Bringing everything into HomeSeer

For the electronics, an ESP32 looks like a reasonable starting point.

It's inexpensive, has plenty of processing capability for the position measurements, and can communicate with HomeSeer over the local network.

The controller could handle sensor readings locally rather than relying on HomeSeer to make every decision.

That's an important design consideration.

For example, if HomeSeer restarts or the network is temporarily unavailable, the obstruction monitoring and local control safeguards should keep functioning.

The ESP32 could report information such as:

HomeSeer Device	Example Value
Garage Door Position	37%
Door Movement	Opening
Door Fully Closed	No
Door Fully Open	No
Opening Obstructed	Yes
Obstruction Location	Lower section
Position Sensor	Healthy
Controller Status	Online

I'd also like to support named positions so that events can request something meaningful, such as Ventilation, rather than requiring a percentage every time.

The interface to the existing Genie opener will need some careful investigation. One option is an electrically isolated control connection, potentially using a relay or an interface to the original remote.

However, we need to understand the opener's control behavior before implementing any automatic positioning. A typical garage door opener wasn't designed to accept a command that says "go to 37%."

We also need to account for unexpected reversals, interrupted movement, manual operation, and discrepancies between the commanded and measured positions.

Simply issuing commands based on elapsed time isn't the reliability I'm looking for.

Designing for the unexpected

A project like this also needs to answer some less exciting, but very important questions.

What happens if the controller loses power halfway through opening the door?

What if the encoder misses a revolution?

What if the garage door is disconnected from the opener and moved manually?

What if an infrared emitter fails, or sunlight overwhelms one of the receivers?

And perhaps most importantly, what happens when two pieces of information disagree?

I prefer to design the system so uncertainty is visible. If the position is unknown, it should report Unknown, not confidently display a potentially incorrect number.

Likewise, an obstruction sensor failure must never be interpreted as proof that the opening is clear.

Any control beyond ordinary status reporting must account for these conditions, and automatic movement should be inhibited when the system cannot confirm it meets its requirements.

The original opener's safety devices and force-reversal mechanisms must remain intact and functional.

Why build it?

Plenty of commercial garage door controllers are available, and for most people, a device that reports Open or Closed and lets them operate the door from their phone is perfectly adequate.

But this is one of those projects where the possibilities are more interesting than the original problem.

It's a chance to combine precision position sensing, microcontrollers, intelligent obstruction detection, and home automation into something both useful and fun to develop.

And since I already use HomeSeer for so many other systems, it makes sense to bring the garage door into that environment with the same level of detail and control.

I haven't settled every hardware decision yet, and there will undoubtedly be a few surprises once I start testing the actual components.

That's usually where things get interesting.

I'll share more as the design progresses, particularly the encoder mounting, the real-world positioning accuracy, and how well the obstruction sensors perform in bright sunlight.

If you've experimented with precise garage door positioning, rotary encoders, or infrared light curtains, I'd be interested in hearing what worked for you and what didn't.

Sometimes knowing whether something is open or closed simply isn't enough.