In 2023, I managed to integrate my garage doors with HomeAssistant using a Shelly Uni device. Controlled remote operation is pretty great, but I wanted to document this project because this solution covers remote door control, door state and even door light control is possible, using a single $12 device with no batteries required. The setup is easy to achieve, and leaves all the garage door opener functionality in tact.

Overview

• Shelly Uni device is powered from a 12v DC power source leeched from the low-voltage side of the garage door control circuit board
• Garage door switch is operated using one of the two potential free outputs on the Shelly Uni
• Garage door state is monitored using both Shelly Uni inputs, detecting open/closed circuits on the garage door opener’s own state sensors
• Light control is not implemented, but could be added to the extra Shelly Uni output in an extremely simple circuit

Shelly Uni

I found the Shelly Uni after having played with a few other devices in the Shelly ecosystem. These devices are excellent. They are easy to set up via captive WiFi portal. They of course join your WiFi network. They can be controlled locally with no cloud services via their own built-in web servers, HomeAssistant, or other local message systems. I have nothing but good things to say about my experience with these devices.

The Uni in particular is well suited for garage door control and state monitoring because of its flexible power input specifications (AC 12V – 24V or DC 12V – 36V), because it can be configured as a momentary switch just like the physical garage door wall-mount button, and has those two inputs which are perfect for observing state which I will get into later.

Getting the Cover Off

One of the trickiest parts of this garage door opener modification was getting the case off. I’m not garage door service pro, so figuring out how to get this case removed was a slow process. Maybe this is easier if you remove the whole unit from the ceiling, but I didn’t want to do that. In the end, I did manage to get the cover off the unit without breaking anything and without the use of a grinder.

With the cover off and the unit safely unplugged, I was able to get a good look at the internals. The bulk of it is obviously the large drive motor, but there are also two circuit boards in the back. You can see the mains voltage connected directly to the smaller brown board, and power leads for the motor and lights leading out.

Power Source

My first order of business was to get these circuit boards off the ceiling and onto the bench for a closer inspection. My plan was to find a suitable power source somewhere on one of these boards, and assume that the load of the tiny Shelly Uni wouldn’t even be noticed. One very easy source appeared to be the step-down transformer which was clearly labeled 22VAC, well within the documented input range of the Shelly Uni. But when I measured the actual potential it was out of range at 28VAC. But on the low voltage side, I found a nice 12VDC right on the connection between the two boards.

I did not feel like soldering directly to the circuit board, so I wrapped the posts of the connector with some solid copper wire before plugging the boards back together and re-assembling.

Door State

The garage door opener unit itself needs to be able to detect when the door is fully opened or fully closed so it can stop the motor. To do this, my unit has a very simple, ingenious, and adjustable mechanism. Through a series of nylon gears, the movement of the door causes a grounded carriage (connected to the gray wire) at the front of the machine to traverse the space between two separate +5V (yellow and brown wire) contacts.

So the potential measured between the yellow and gray wires is 0 when the door is fully open and +5V when not fully open. The potential between the brown and gray wires is 0 when the door is fully closed and +5V when the door not fully closed. So with these three contacts, and the two inputs on the Shelly Uni, we can know when the door is fully open, when it is fully closed and when it is neither.

All that was left was to wire it up and find a place for the Shelly Uni to live. I wasn’t sure about packing it all into the metal garage door casing. In hindsight, I probably could have managed it and it would have looked nicer. But I wound up drilling a hole in the case and routing the cables through a rubber grommet on top.

It has been over a year now and this setup has been working great on both my garage door openers. I have it integrated with HomeAssistant which makes for very convenient remote operation. At one point, wall-mounted button was sticking and I believe the stuck button somehow triggered a factory reset of the Shelly device. But I did clean that plastic switch and lubricated it with mineral oil and it hasn’t had a problem since.

HomeAssistant Configuration

You don’t need to use HomeAssistant to make use of this setup, but it is quite nice. In HomeAssistant, garage doors can use the ‘cover’ template and my configuration looks like this:

cover:
  - platform: template
    covers:
      garage_door_right:
        device_class: garage
        friendly_name: "Garage Door - Right"
        unique_id: garage_door_right
        position_template: >-
          {% if (is_state('binary_sensor.garage_door_right_channel_1_input','on') and is_state('binary_sensor.garage_door_right_channel_2_input','on')) %}
            {{50|int}}
          {% elif is_state('binary_sensor.garage_door_right_channel_1_input','on') %}
            {{0|int}}
          {% elif is_state('binary_sensor.garage_door_right_channel_2_input','on') %}
            {{100|int}}
          {% endif %}
        open_cover:
          service: switch.turn_on
          data:
            entity_id: switch.garage_door_right_channel_2
        close_cover:
          service: switch.turn_on
          data:
            entity_id: switch.garage_door_right_channel_2

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A binary clock is hardly a new idea, but this particular concept is something I haven’t seen anywhere else. And it was idling in the back of my mind for over a decade before finally seeing a working prototype.

Concept

The passage of time can be measured in any number of ways, but when a clock is designed for humans, I think it should be based on a natural concept. Since I live on Earth, I designed a clock, as many others have, based on the smallest natural temporal concept I can readily observe: the day.

The day is plenty useful for medium-term planning, but it lacks the precision needed for many purposes, and so it must be divided in order to build a useful clock. This is where clock design becomes much more arbitrary. Dividing the day into 24 was supposedly based on astronomical observations of various stars passing in the night, but beyond that, there’s no natural reason there should be 60 minutes in an hour and so on.

My thought, is that the simplest and most natural way to divide a day would be in half. This is essentially the AM/PM indicator which is a concept so natural and necessary, that even many of our 12 hour clocks use it to avoid the otherwise ambiguous information displayed. But if the most natural way to divide a day is in two, then maybe the next most natural division is in two again. Dividing a day repeatedly in two results in a kind of binary clock. And this is exactly the concept.

Design

Let’s explore the design I’ve had in mind. This idea has taken many shapes in my head over the years, but the picture I’ve had in mind most often is a series of LEDs, each representing a successive division of one full day.

For a practical, human-oriented clock, we’ll need enough precision to be useful for normal human activity. One single LED cuts the day in half, providing half-day precision, but that’s far too granular to be able to plan intra-day activities. Adding two more LEDs takes the precision down to 1/8th, and with four you get 1/16th of a day. For any number of LEDs, the precision of this clock is 1 / (2 ^ n).

Since this way of dividing days is unfamiliar, let’s look at further divisions to see what it would take to end up with a useful clock. Each item below shows the level of precision (in 24 hour terms, rounded to the nearest second) that could be reached with the given number of LEDs:

1. 12:00:00
2. 06:00:00
3. 03:00:00
4. 01:30:00
5. 00:45:00
6. 00:22:30
7. 00:11:15
8. 00:05:38
9. 00:02:49
10. 00:01:24
11. 00:00:42
12. 00:00:21
13. 00:00:11
14. 00:00:05
15. 00:00:03
16. 00:00:01

In order to approach one second precision, we would need 16 individual LEDs. And even that final light would represent a period of time slightly longer than a second. But down-to-the-second precision isn’t often required in day to day human activity. Since I want to learn to read my own clock, I decided to try to keep the display as simple as possible, and that means using as few lights as I can get away with.

Eight LEDs give me a good balance. I don’t usually need more precision than I can get out of eight bits and keeping the LED count down to eight should make the clock easier to read. Here are a few examples of how this clock display could be translated into conventional 12/24 hour format.

o o o o o o o o <-> 12:00:00am
o x o o o o o o <-> 06:00:00am
x o x o o o o o <-> 03:00:00pm
x o x x o o o o <-> 04:30:00pm
x x x o x x x o <-> 10:18:45pm

The first few digits are very easy to learn to read, but they get more difficult if you plan on translating them to the convetional format in your head. One of the things I’m most curious about, is how hard it will be to learn to understand the meaning of this clock without having to do the conversion.

The information in the clock gets progressively more granular as you read from left to right. It may be that the first 4 LEDs can give you all the precision you need, but as with a conventional digital clock, you can decide where to stop reading when you’ve gathered enough information.

Hardware

The recent explosion in the number of low-cost WiFi enabled development platforms was the driving force behind why I finally started on this project. Previous systems were either too bulky, power hungry and expensive, or would have required a lot more effort on my part.

In order to avoid implementing a system for manually setting the current time on this clock, I wanted a platform that included easy internet connectivity so the clock could set itself using NTP. For me, WiFi was part of this requirement along with all the nice network interface features we’ve come to know and love like DHCP support and a working TCP stack and preferably HTTPS support in case I want to get really fancy.

Of course, a real-time clock (RTC) is important when building a clock and it’s nice to have one built-in. It’s always possible to add your own, but my hardware experience is limited and a microcontroller that includes an RTC allows me to skip that hurdle. I also wanted enough I/O pins with enough power to drive 8 LEDs so as to not require fancy multiplexing or extra circuitry. Other concerns are power consumption, cost, and how easy the platform will be for a software person like me to learn.

In the past, for WiFi connected projects, I’ve used arduino and a repurposed wireless home router because those were the best options available at the time. But today, there are all kinds of other interesting options. WiPy is the one I ended up on for no particular reason other than I found it early on in my search and it ticks all my requirement boxes.

One other interesting thing about the WiPy is that you can write software for it using tiny version of Python called MicroPython. For me, this is an advantage over alternatives like Wiring/Processing which I’ve battled before. Python is a more comfortable environment.

Software

True to my open source roots, I created a GitHub project to house and track the evolution of the software that drives Byte Clock. I likely won’t do a whole post on how the software works because it will likely evolve and anyone with sufficient interest can keep an eye on the GitHub project for updates. It’s enough to say that the software is responsible for synchronizing the real time clock with an NTP server and managing the state of the clock’s display.

Blinking an LED

In addition to the WiPy microcontroller, I bought a cheap 3.3v power supply from Amazon and a bread board. The power supply takes 6.5-12v DC input and provides 3.3v or 5v DC output. In this photo, I’ve got the power supply and the WiPy connected on the bread board. Here’s what it looks like powered on for the first time.

Getting up and running with the WiPy was pretty simple once I figured it out. When the WiPy powers on for the first time, it creates its own wireless network which anyone can join and from there you can upload your own code over FTP. Adafruit has a handy guide with more detail on how to get started.

Here’s a very exciting video of the moment when I made it past the first hurdle, blinking an LED.

Setting Up the Display

The clock display amounts to a binary counter, so that was a natural next step. I chose eight different colored LEDs and hooked them up to the first eight I/O pins on the WiPy. The various colors have differing forward voltage V_f values and different brightness properties. In order to roughly match the brightness levels, I had to choose different current limiting resistor values for each one. Attempting to match the current of each LED methematically resulted in wildly differing brightness levels, so choosing the right resistor values ended up being a lot of trial and error.

The display test program didn’t take long to write. Here it is in action.

Implementing the Clock

With the LEDs connected to the WiPy and the WiPy connected to the internet, the rest is software.

It would have been awesome to build a Byte Clock without having to use a conventional clock to drive it, but that was the simplest available option. If you examine the source code, you’ll see the time keeping is done using the MicroPython RTC class. The system boots, grabs the current time from an NTP server, sets the real-time clock and sets a timer to increment the display state every interval.

Next

I’ve had this clock running on my kitchen counter for a few months and it’s still keeping accurate time aside from missing the time change. I’ll need to implement that function. Thinking about this clock has made me ask all kinds of questions about the nature of conventional clocks and how we go about our days.

For instance, why should clocks start at midnight? And what exactly is midnight by the way? Would it make sense for clocks to start counting at sunrise or noon instead? It might, and I haven’t ruled out playing with that idea. But going down that road makes conversion to convetional 24 hour time a lot more difficult.

Why should clocks count up and not down? We could just as easily design a clock that counts down the time remaining in each day. Would that be good?

Communicating information about moments in time with the byte clock is presents a challenge. Reading all eight digits aloud would be inconvenient (“on off on on on off off on”). But since this is a Byte Clock, the time could be expressed with just two hexadecimal digits (b9). That’s a pretty concise way to express the time of day at this level of precision.

After pondering the differences between the Byte Clock and conventional clocks, it seems more clear that the values 24 and 60 are not at all arbitrary. Conventional clocks are easily divided in half, thirds, fourths, sixths and eigths. The Byte Clock is, of course, only divided easily by powers of two. I think I knew this all along, but having built this clock makes me appreciate this aspect of conventional clocks.

Next, I’m planning to play with the arrangement of the LEDs with the goal of making the clock easier to read. And after that, I’d like to design a slick looking case and build something that looks a bit more professional.

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Having been thoroughly satisfied with prior HP printer experiences, I made the mistake of purchasing a brand new HP Photosmart c7280. I’m a big fan of these all-in-one devices. I especially like having a WiFi interface, and scanning to a USB disk as opposed to some ridiculous TWAIN protocol is such a great idea it’s hard to imagine why some devices still don’t support it. But all the things I love about this printer are outweighed by the horrible ink system.

Lets start with the most obvious problem with these ink cartridges. They’re way too small, the color cartridges are only 11 mL. I’ve seen claims that they can yield up to 500 pages. I have no data to argue with that figure, but I can tell you it seems very high compared to what I’ve seen.

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In part 1 of this series, I took an Asus router and loaded openwrt onto it. I added an LCD display and connected it to the serial port on the router board. At this point, I have a low-power, small form factor computer that I can customize to my heart’s content. As far as I/O, the computer still has its original wifi antenna, 5 wired LAN interfaces, a serial port and a USB port. My USB sound adapter still hasn’t arrived from Hong Kong, so I’m going to work on another piece of the puzzle.

The first thing I did after joining this device to my wifi network was telnet in and change my password. Now the project that I’ve been following up to this point is mainly to be used for playing internet radio stations as I understand it. My wifi radio is going to be used for that too, but also for playing selections from my own music library. I plan to get one of these Buffalo 1TB Linkstation NAS devices and put all my media on it and leave it down in the basement. I’ve read that you can really customize these devices, but all I need to do is add an ssh server to it. Then I can mount the whole filesystem to a folder on my wifi radio and have access to a full terabyte of storage space.

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I’ve been inspired by Jeff Keyzer to build a wifi radio. I’ve wanted for a long time to build a wifi radio to play internet radio and music from an arbitrary remote filesystem. The low cost of the platform he chose, the WL-520gu which I picked up for $35 shipped and is now even cheaper made the barrier to entry much lower than I had thought. So I bought one and tore out the guts as soon as it arrived.

mightyOhm has a good series of blog entries for doing almost exactly what I want to do. I skipped the first bit about hooking up a terminal because I don’t have a TTL-USB device lying around and flashed the router with openwrt. As I found out, TTL is not RS-232. You can’t just connect an RS-232 cable to your PC and solder the other end to the serial pins on your router. I do have a TTL LCD panel that I picked up last year on eBay (I’ve been planning to build a device like this for some time). Modern Device has these 20x4 character blue LCDs with a TTL serial interface for around $30. Jeff built his own, but he’s also an electrical engineer.

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