You may get better results by using both indoor and outdoor lux sensors. Depending on the sun position, room layouts and window locations there can be a quite a difference in outdoor and indoor lux levels, which might interfere with your automations.

I use a combination of Aqara Zigbee motion sensors, which also have a lux sensor, a couple of dedicated lux sensors, and my outdoor security cameras which have a day and night sensor.

You can always try it with one and add more if you need more granularity. Every smart home is different.

You might be able to get a long way without the sensors. Using a weather sensor + sunrise/sunset sensors?

I think just one sensor for outside is enough, you'll probably need to experiment with the "bright" and "dark" values. Leave a decent gap in between the two bright and dark values to avoid the blinds bouncing up and down.

You can probably make the sensor yourself with a LDR (light dependant resistor) and a microcontroller (esp32 or similar)

Can't you just use time as an input? That's how I control the brightness of my lights

One sensor should be enough. I believe they usually mount onto the inside of the window facing outwards so that lights and movement in the room don't influence it.

The simplest way of solving this would be with technically four separate automations. However you can place them all in the same HA Automation using multiple triggers and trigger IDs. (Or have one for the blinds and one for the lights with two triggers each)

I'm going to assume the blinds are somewhat light translucent.

For the blinds use a numeric trigger that fires if the lux value is over some threshold for let's say 10 minutes. That way it won't trigger for every tiny cloud. When triggered lower the blinds.

Add another numeric trigger for moving back up when the lux value is under some threshold for 10 mins. Test to make sure that lowering or raising the blinds doesn't darken or lighten the room enough to immediately have it trigger the other trigger. If it does then increase the difference between the two thresholds.

Copy the same procedure for the lights. The timer can be shorter here, maybe try 1 minute. Make sure that the thresholds are low enough as otherwise lowering the blinds would immediately turn the lights on. I would suggest first tuning the blind triggers and then tuning the light thresholds to your liking.

If you can't set the light thresholds low enough so that the blinds don't interfere with them you'll need a somewhat smarter automation but I'd try the easy way first.

I've made an automation that uses sun azimuth as the trigger (window is otherwise shaded), with outside temperature and cloud cover conditions so it'll stay open if it's cloudy or cool outside. You could add cloud cover triggers to activate while the sun is in the azimuth range to open the blind if it goes from sunny to cloudy too. Toggling the light can be an action alongside the blind.

I use the met.no integration for temperature and cloud cover entities.

the 'actual daylight level' is my main automation trigger. I used to do it using the azimuth but that didn't cover rainy days or days with a clouded sky so I added the lux sensor of my outside motion sensor into this. until the battery went out during a holiday. I now have a template sensor named 'reliable light level'. It uses the actual lux sensor as the main value, if that is not available I use the sun azimuth and do some calculations with the date and time to get a light level. after that it was a bit of trying things out to find the perfect levels for

• turn on light in the staircase with motion
• turn the staircase lights on completely
• shut the blinds when it's too sunny

I do this by activating different mode booleans (dim, dark, light) so the automations are triggered by them turning on or off and Incan also check the state of these in the automation conditions.