Creating a "last motion" helper/template entity for a motion sensor?

mike15 · February 8, 2026, 9:54pm

I feel like this should be a simple one but I’m struggling with it and would love advice!

I have a motion sensor that contains a “binary sensor” entity that indicates motion status. I would like to create a second entity that contains the time and date of last motion detected (i.e., the last time that the binary sensor changed state to “Detected”). I’m assuming this will require creating a “helper” of type “template” and then entering the appropriate formula for the template’s state but I can’t seem to figure out what that is.

FWIW, I found this 2yr old thread from someone who seems to have had a similar problem, and it looks like there is YAML code for a solution, but I’m not actually sure where to paste in this YAML code (and do I also need to create a helper to represent the “variable” that is being updated every time there is a state change, etc.) I’d rather just create a helper using the GUI if there’s a straightforward way to do that…

Thanks in advance!

Nick4 · February 8, 2026, 10:07pm

Hi Mike, rough guideline:

create a date/time helper in with the desired name
create an automation with the trigger if motion is detected and in the action set the value of the helper

vic4news · February 8, 2026, 10:19pm

Here’s an automation I use when my Ip address changes similar to what you want for your motion detector.


alias: ip_address_changed
description: ""
trigger:
  - platform: state
    entity_id:
      - sensor.public_ip_address
condition:
  - condition: template
    value_template: "{{ trigger.from_state.state not in ['unavailable', ''] }}"
  - condition: template
    value_template: "{{ trigger.to_state.state not in ['unknown', 'unavailable',''] }}"
  - condition: template
    value_template: "{{ trigger.from_state.state != trigger.to_state.state}}"
action:
  - service: input_datetime.set_datetime
    data:
      datetime: "{{ now().timestamp() | timestamp_local }}"
    target:
      entity_id: input_datetime.ip_address_changed
mode: single

mike15 · February 8, 2026, 10:39pm

Thanks @Nick4 and @vic4news, but I think I’m struggling with something a little more basic. I totally understand the concept of having an action triggered by a state change and that action sets a variable to a value equal to the current time… I just don’t know how to create a “variable” in home assistant or how to set its value as part of an automation.

@vic4news : I don’t know where to type in that code you’ve given me.

@Nick4 : which of the many different types of “helpers” should I create in order to have what is effectively a variable of type time (and date)? And where in the “create new automation” GUI is the action type that is set the value of a variable (and where do I enter the formula that looks something like “now()”)?

Thanks!

Nick4 · February 8, 2026, 11:00pm

mike15 · February 8, 2026, 11:17pm

Thanks @Nick4 !

I’ve created the helper, and it looks like I need to use action of type “input datetime: set”. But when I entered “{{ now() }}” as the value, it seems to be working

However, when I try to display this helper in a dashboard it shows an interactive form to enter a date and time, rather than the convenient “19 minutes ago” that is shown on my more sophisticated motion sensors (or, rather, motion sensors with more-sophisticated Home Assistant integrations) that have this behavior built in. Is there something I can do to easily mimic that behavior?

Thanks!

Nick4 · February 9, 2026, 8:32am

Did you add the helper as card?
You have to add a card that displays the value of that helper.

reste_narquois · February 9, 2026, 9:03am

If you are using the entities card to show your helper, set the entity type to simple-entity and that should force it to show the state rather than the special row format of a time/date entry form.

You could also try experimenting with the format key to display the value in different ways, but I’m not 100% sure it works for helpers - the docs mention timestamp sensors only, so possibly not.

mike15 · February 9, 2026, 1:28pm

Thanks. I have a bunch of other sensors (different brand, different integration) that come with a prebuilt “last motion” sensor entity that appears by default as uneditable, continuously-increasing text like “17 minutes ago” or “3 weeks ago” etc. I have these listed in an entity card in a dashboard. I’d just like to add a row for this new motion sensor that looks like all the others.

I could not find options in the dashboard editor interface to change the “format” for a row… The only options it gives me are to override the name or to show secondary data.

Nick4 · February 9, 2026, 2:55pm

Is your original issue solved?

reste_narquois · February 9, 2026, 5:18pm

Entity card or entities card? They are not the same thing

I’m not in front of a PC, and normally edit my dashboards in YAML, but I’ll try and do some screenshots in due course.

EDIT: if using the entities card, it looks like you need to use the code editor to set these options:

You can ignore the errors about the visual editor not being supported: the preview on the right shows what it looks like.

As I suspected the format key does not work for a date/time helper. If you absolutely want the relative time displayed, you will probably need to make a trigger template timestamp sensor. This will involve using YAML to configure it though.

busman · February 10, 2026, 1:39am

You used the right word there. I think you want a sensor.

template:
  - triggers:
      - trigger: state
        entity_id: binary_sensor.hall_motion
        to: "on"
    sensor:
      - name: Last Hall Motion
        unique_id: last_hall_motion_id
        device_class: timestamp
        state: "{{ now() }}"

Then in a dashboard it would look like:

mike15 · February 10, 2026, 3:02am

Thanks @busman ! That looks like what I want… but where do I enter the code you have written?

busman · February 10, 2026, 5:18am

There’s a few options. The most common would be in whatever file you have configured for templates, for example in my configuration.yaml I have this, which is probably the same as yours:

automation: !include automations.yaml
script: !include scripts.yaml
scene: !include scenes.yaml
sensor: !include sensors.yaml
template: !include template_sensors.yaml

And in that case you can see that the template: value is brought in from template_sensors.yaml and in that file:

- triggers:
    - trigger: state
      entity_id: binary_sensor.hall_motion
      to: "on"
  sensor:
    - name: Last Hall Motion two
      unique_id: last_hall_motion_two_id
      device_class: timestamp
      state: "{{ now() }}"

This explains creating template sensors:

mike15 · February 10, 2026, 2:52pm

@busman Thanks… I have created my templates by going the Settings section of the Home Assistant UI, then choosing Helpers, then clicking the button to create a new helper…

So again, I’m not sure where to enter this code…

busman · February 10, 2026, 3:05pm

As you can imagine, there are configuration files in HA and some you can edit in the UI but others you need to edit using a file editor (there’s an Add-on (“App”) for that) or you need to have shell access to HA core.

Do you have experience with the using the shell, editors and SSH?

There’s an endless amount of info online about how to edit files in HA. The first link on a google search was this video, but you can find something that works for you, I’m sure. This is also an area where AI won’t completely suck at providing some basic understanding.

Ask questions here if things are still not clear after researching this.

mike15 · February 10, 2026, 3:19pm

Thanks! Yep, I’m quite familiar with using shells, SSH, etc… and I’m able to browse the directory structure on my HA device and edit files.

I just don’t know where in the HA directory structure the relevant file(s) is/are to add this sort of thing – or where in those files to do so. … or the correspondence between any of this and the options in the Home Assistant GUI.

I’ve found references to the YAML format (though maddeningly they only cover syntax – kind of like trying to figure out how to host a website by memorizing HTML attributes), but I’d be very grateful for any written primer on this side of Home Assistant that you could point me to…

Thanks!

busman · February 10, 2026, 3:35pm

Install the “Advanced SSH & Web Terminal” Add-on/App and poke around.

$ ssh ha

       ▄██▄           _   _
     ▄██████▄        | | | | ___  _ __ ___   ___
   ▄████▀▀████▄      | |_| |/ _ \| '_ ` _ \ / _ \
 ▄█████    █████▄    |  _  | (_) | | | | | |  __/
▄██████▄  ▄██████▄   |_| |_|\___/|_| |_| |_|\___|          _
████████  ██▀  ▀██      / \   ___ ___(_)___| |_ __ _ _ __ | |_
███▀▀███  ██   ▄██     / _ \ / __/ __| / __| __/ _` | '_ \| __|
██    ██  ▀ ▄█████    / ___ \\__ \__ \ \__ \ || (_| | | | | |_
███▄▄ ▀█  ▄███████   /_/   \_\___/___/_|___/\__\__,_|_| |_|\__|
▀█████▄   ███████▀

Welcome to the Home Assistant command line interface.

Home Assistant Supervisor is running!
System information:
  IPv4 addresses for enp6s18: 192.168.0.70/24
  IPv6 addresses for enp6s18: fe80::35ae:e8b8:6425:a2b/64

  OS Version:               Home Assistant OS 17.0
  Home Assistant Core:      2026.2.0

  Home Assistant URL:       http://homeassistant.local:8123
  Observer URL:             http://homeassistant.local:4357

System is ready! Use browser or app to configure.
➜  ~ cd config
➜  config ls *.yaml
automations.yaml           input_number.yaml          scripts.yaml               template_sensors.yaml
configuration.yaml         irrigation_unlimited.yaml  secrets.yaml               test_auto.yaml
customize.yaml             scenes.yaml                sensors.yaml

➜  config head -18 template_sensors.yaml
# Device Classes: https://www.home-assistant.io/integrations/homeassistant/#device-class
# https://www.home-assistant.io/integrations/binary_sensor/#device-class
# Remember, you can either have multiple "^-sensor" or a list of sensors below a single one.
#
# These are more of a one-off, so in this file. Once there's a few template sensors
# that are related to a give function (irrigation, heating, etc.) then maybe put those
# into packages.

- triggers:
    - trigger: state
      entity_id: binary_sensor.hall_motion
      to: "on"
  sensor:
    - name: Last Hall Motion TWO
      unique_id: last_hall_motion_two_id
      device_class: timestamp
      state: "{{ now() }}"

Seriously, there’s a ton of stuff online if you poke around.

YAML is just syntax. It’s just, eh, yet another markup language. Is JSON more familiar to you? If so there’s YAML-JSON converters online for playing with to see how the format works. It’s just a way to represent scalars, lists and dictionaries. The specifics for how it is used with HA is in the template sensor docs I posted.

Again, just dive in and poke at it. It’s hard at first then it’s not. When you have a specific question about something then this is the place to ask.

That’s a lot of poking…

mike15 · February 24, 2026, 4:55am

Thanks, but that’s kind of unhelpful. If you want a specific question could you please simply tell me which file you intended me to add this code to? Or, again, if there is any reasonable primer on this part of Home Assistant you can point me to, which I could read and then have a good chance of answering the question, I’d take that as well…

busman · February 24, 2026, 5:20am

That code above is prefixed with the file names.

for example in my configuration.yaml

And following that shows:

template: !include template_sensors.yaml

And right below that it says:

template_sensors.yaml and in that file:

- triggers:
    - trigger: state
      entity_id: binary_sensor.hall_motion
      to: "on"
  sensor:
    - name: Last Hall Motion two
      unique_id: last_hall_motion_two_id
      device_class: timestamp
      state: "{{ now() }}"

Is that what you are asking about?