Adding Brightness Sensor to Lights Logic

[Michael Ingraham]

I am using Sonoff Basic switches to turn on some lights in out home. I have flashed the switches with TASMOTA. I am using openHAB to set up logic conditions for controlling different lights in the house. The rules use a combination of sun elevation, sunset/sunrise offset, and our location (i.e., are we home). Unfortunately, sun elevation and sunset/sunrise don't account for the actual "darkness" in some of our rooms (e.g., when it's overcast). I need to add a brightness sensor to the mix.

Options?

• An "adjustable" sensor that I can "plug in" to GPIO 14 on the Sonoff that will trigger an on/off input to tell me the brightness has reached a certain threshold?
  
• A "standalone" brightness monitor that will publish (ideally state messages via MQTT) it's readings? If not a push setup, I can poll the device periodically (again, MQTT?).
  
• ...
  

Your experiences and advice are appreciated.

Regards.

Mike

[Philip Knowles]

I think that you could do it quite easily with a light dependent resistor to A0 on an ESP12 device such as a LoLin.. You’d just need a dropping resistor drop the voltage to 1V and possibly a potentiometer

 

Regards

 

Phil K

 

Sent from Mail for Windows 10

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[Michael Ingraham]

Phil,

First and foremost, thank you!

Is this the circuit as you describe?

Quick search for Lolin popped up "Lolin D32".

1. Is this the module you meant?
   
2. From the looks of it, this could be flashed with TASMOTA?
   
• If so, is flashing this the same as flashing a NodeMCU?
  
3. Is the upload directly through the microUSB port? Or do I have to connect leads to RX/TX etc.?
   
4. How do you put the Lolin in programming mode?
   
5. Is there a Lolin TASMOTA module type or do I choose Generic?
   
6. Does TASMOTA report the LDR reading as a numeric value?

Regards.

Mike

[Philip Knowles]

Your circuit is almost right but the LDR would be between A0 and 0V and the 10k resistor between 3.3V and A0. At least that's how I would do it. From memory LDRs resistance decreases with increasing light intensity so the voltage would increase and, again from memory, I think the max voltage at A0 is supposed to be 1V but I may be wrong. If you're allowed 3.3V your circuit would give you a larger number with brighter light so is more intuitive.
The Lolins are also known as Wemos. The Lolin V3 is slightly bigger. Search for ESP-12 E.
The latest allsensors.bin has A0 set as Analogue input as standard and just select the generic module.
Hope that helps

Regards

Phil K

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[Philip Knowles]

They have a Flash button next to the USB input

Regards

Phil K

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