The information below assumes some competency with home assistant and an existing z-wave setup. You can use a different multi relay device with a different protocol but you'll need to make sure it will work with your set up.

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What problem was I solving?

My wife and I have been going on walks pretty regularly with our newborn and we keep our stroller in the garage. Every time we come back from our walk it's a pain to type in the code next to the garage door and wait for the door to open. It would be great to use home assistant to open up the garage as we approach it. We could just put a garage door opener remote in the stroller but where's the fun in that? I want to be able to open the garage door from my phone!

As I was solving this problem and connecting my car's homelink buttons to the garage, I thought to myself... wouldn't it be nice to be able to use the other 2 buttons on my rear view mirror to lock and unlock my front door since we park our car in the driveway and typically have our hands full with groceries and/or the baby. I know that we could automate this via presence detection but we didn't want an unlock mechanism based on location since we only wanted that to happen with our explicit input. An alternative is to whip out my phone, unlock it, open home assistant, and hit the unlock button but that's way more steps than just hitting a physical button in front of me.

What was the high level solution?

So there are really two problems to solve here. One is, how do I make my garage door smart and the second is, how do I make those homelink buttons trigger home assistant automations.

I've separated those two problems into separate sections.

Making the garage door smart

There is actually pretty good documentation for how to do this with Zooz's Zen16 multirelay. I'm using the second wiring diagram BUT also plugging in a reed switch into Sw1 so home assistant can know whether or not the door is open. The documentation suggests using a tilt sensor but those are $25+shipping and a reed sensor is $4 and never runs out of battery. I'll get into the reed sensor stuff later.

Making the homelink buttons trigger home assistant automations

At the end of the day, those homelink buttons are just transmitting radio frequencies so I needed some device that could consume those radio frequencies and then let home assistant know when a message came in. I already had the Zen16 multirelay so I just needed something to tell the Zen16 when a radio message came in. I picked up a Liftmaster 850LM which could be programmed with the homelink buttons and then wired into the Zen16.

Stuff you'll need to buy

• mini screw driver + mini flathead
• Liftmaster 850LM
• Zooz's Zen16 Multirelay
• 20/2 bell wire
• bell wire nuts
• wire cutter and stripper
• Reed sensor (alternatively you can buy a zwave battery powered sensor)
• Optional: Garage door remote

Installation

Disclaimer: I am not an electrician so if you don't know what you're doing with the wiring, please hire a professional. All that being said, the voltages I was working with were all low or with dry contacts so I felt comfortable DIYing it.

Here's a full wiring diagram

Before I get into the explanation, it may be helpful to use this wiring diagram as a high level overview.

Link to interactive diagram

Connecting the Liftmaster 850LM to the Zen16 for homelink automations

It may seem unintuitive because it's the more complicated work, but doing this part before the garage door was super helpful because I could test everything at my desk instead of getting on a ladder to troubleshoot and rewire stuff when it wasn't working

Wiring the 850LM

This wasn't actually that bad, connect the 850LM's Operator 2 NC and COM contacts to the Zen16 Sw2 and the Operator 3 NC and COM contacts to the Zen16 Sw3. So whenever the 850LM receiver hears a message come in on frequency 2, it will complete the circuit on operator 2, which tells the Zen16's Sw2 that the circuit is closed and something has changed. Same thing will happen for when a message comes in on frequency 3.

Connecting homelink to the 850LM

So now that you've got everything wired, you'll want to follow the instructions on the 850LM manual and your car's homelink instructions. Personally, I got a remote like this one and connected it to the 850LM. Then used the remote to program the homelink buttons. It was more convenient than using an extension cord on the 850LM to get close to my car. If you press a button on the remote, you should hear a little click on the 850LM as well as the little LED lighting up.

Testing

I found it useful to connect the Zen16 to home assistant and testing my automations before mounting everything which, like I said earlier, would require me to get on a ladder to troubleshoot. What I did was just connect two wires to Sw(1/2/3) and just tapped them together to simulate the reed switches or the 850LM receiving a button click. Go down to Home assistant configuration to see how to configure this from the software side so you can test your automations.

Making the garage door smart

Setting up the reed sensors

Reed sensors are essentially a mechanism to detect if something is closed or open. When the two little components come close together, one of them has a magnet that moves an electrical gate which will either close or open a circuit. Here's a picture of what I set up on my garage door: When the garage door is closed, the two pieces are very close together and complete the circuit.

When I open the garage door it looks like this:

I used 20/2 bell wire to wire the sensors and those plugged into the Sw1 contacts on the Zen16. It doesn't matter which wires go to which contacts since you're just detecting if a circuit is complete but for the reed sensor, one wire needs to connect to C(the common wire) and the other should connect to NC(normally closed) or NO(normally open). I chose to connect to NC.

Before you install the sensors, take the two pieces and put them close to your ear, then move them away from each other. You'll hear a little click which indicates the magnetic piece is moving. That's how close they need to be to each other to be working.

You'll need to get creative about where you install the reed sensor based on your door but I just put a little piece of wood on the top of the door, glued one end of the sensor to that wooden block and drilled the wired side into the wall as you can see:

Wiring up the garage door to the Zen16

So now that you have the Reed sensor attached to your Zen16 you can tell when the garage door is open or closed... but how do you actually close/open the garage door with home assistant? I wanted to use my already wired garage door button as a fallback so I just used a wirenut to connect both the garage door button AND the wires going to the R1 contacts from the Zen16, then I took the wires coming out of that wirenut and plugged them into my garage door opener as you can see here:

Mounting

I wanted the electronics in my garage next to my garage door motor which already have an outlet. I mounted some scrap wood to a ceiling joist like this.

Then I just mounted the 850LM and Zen16 onto the block

Home assistant configuration

Once you connect your Zen16 to home assistant you'll need to make some config changes. Please refer to the Zen16 documentation as some things may change.

1. Parameter 2 - Set this to Open/Close alert(Door sensor), This is your reed switch that determines if your garage door is open or closed
2. Parameter 3 - Set this to Momentary, this is your operator 2 from the 850LM. A momentary switch is what it sounds like, it closes the circuit for a moment which triggers your switch
3. Parameter 4 - Set this to Momentary, this is your operator 3 from the 850LM.
4. Parameter 6 - Set this to 1. This is so when you flip the garage door relay to open/close it, you reset the relay state back to off. This simulates the behavior of a momentary switch. If you don't do this, when you want to close/open the garage door you'll need to turn the relay off which means every action will require a "double click"
5. Parameter 12 - Set this to off. This one is super important. It separates your reed sensor on Sw1 from controlling the R1 relay. If you don't do this, every time your reed sensor changes state, it'll flip the relay which will re-open your garage as soon as it closes.
6. Parameter 15 - Set this to Seconds so your parameter 6 means "1 second"

With Parameter 12 set to off, home assistant will create a new sensor entity to demonstrate the state of your reed sensor(eg. whether or not your garage is open). In order to see this new entity, you'll need to exclude then re-include the Zen16(you may also need to re-interview the device after re-including it)... pretty annoying but the instruction comes straight from the aforementioned documentation:

IMPORTANT: If you set this parameter to value 4-11, you’ll need to exclude and re-include the device (without changing any settings) so that a child device is created for the input of your choice!

Now you've got that all set up, you should create an automation for when your multirelay's Sw2 and Sw3 are triggered from your 850LM. Here's an example of my home assistant automation yaml where I have my 2nd homelink button unlocking my door and the 3rd homelink button locking my door.

alias: multirelay automations
description: ""
triggers:
  - trigger: state
    entity_id:
      - switch.garage_multirelay_2
    id: 2 - unlock door
  - trigger: state
    entity_id:
      - switch.garage_multirelay_3
    id: 3 - lock door
conditions: []
actions:
  - choose:
      - conditions:
          - condition: trigger
            id:
              - 2 - unlock door
        sequence:
          - action: lock.unlock
            metadata: {}
            target:
              entity_id: lock.front_door_lock
            data: {}
      - conditions:
          - condition: trigger
            id:
              - 3 - lock door
        sequence:
          - action: lock.lock
            metadata: {}
            target:
              entity_id: lock.front_door_lock
            data: {}
mode: single

As for the garage door opener and sensor. You can set that up any which way you like. Treat it like a normal button to open something and a sensor to detect if something is on/off(or rather open/closed).

How it all works

The finished product looks sort of like a drunk handyman's work... but hey, it allows me to smoothly bring my stroller back inside after my walk and unlock my front door very easily before my hands are full of groceries/baby.

Here's how my door gets unlocked. I press the homelink button in my car. A radio signal gets picked up by the Liftmaster 850LM which closes a circuit. That closed circuit is then picked up by the Zen16 multirelay which changes a home assistant switch state from off to on. My home assistant automation picks up a state change and then performs the unlock action.

Here's how my garage door is opened. I go into home assistant and hit the multi relay switch(in this case R1). This closes a circuit in the multirelay which my dumb garage door thinks is a signal from the button on the wall and opens/closes the garage door.

Security considerations now that rf controls my front door

• The 850LM supports rolling codes so there are really only 3 reasonable attack vectors
  • Someone stakes out our house and tries to pick up the signal that is sent out when we click one of the buttons
  • Either our car or a garage remote is stolen
    • Police recommend that you don’t keep garage remotes in your car since someone can break into your car and steal it. Can’t really do that with homelink since they would need to steal your entire car.
  • Someone(eg. Valet) has access to your car and can copy the signal onto their own remote
• The solution here is the same for all issues, you can have your home assistant automation check that someone is home before performing any action
  • Caveat, I have homelink/the remote opening the garage door directly and not going through the zen16 so I can’t check for presence if someone steals my car and uses it to open my garage. If someone got into my garage they can steal all the stuff in my garage and they would likely close the garage door behind them and use my own tools to break into my house 🙁. If this is something you’re concerned about you do should use a slightly different set up where you have the 850LM wired into the zen16 switch and then the corresponding relay will open the garage, that way you have control over whether the garage door opens.
    • The zen16 only has 3 switches so i didn’t have space to do this, I would have needed to sacrifice the reed sensor connection. I also wanted to simplify the set up as much as possible and hooking the remote directly into the garage door opener was an option here.