Lightdome.

360° Lux Measurement with nodeMCU

• Measures the lux from four sides (N,E,S,W) with photo-resistors.
• Publish the values via MQTT
• Set factor, offset and interval per MQTT at runtime

Hardware

• 1 x nodeMCU
• 1 x Analog-Digital-Converter per I2C: ADS1115
• 4 x Photo-Resistors
• 4 x 10K Ohm Resistors

Wiring:

• nodeMCU - ADS1115

 - D1 -> SCL  
 - D2 -> SDA  
 - 3V -> VIN
 - G  -> G

• Photorestistors

 - Pin 1 -> 3V (nodeMCU)
 - Pin 2 -> A0 (ADS1115)
         -> 10k Resistor -> G (nodeMCU)

Setup

• duplicate the config.h.default as config.h
• change the file at your own

Use

The device reconnects automatically to the given wifi accesspoint. Then it reconnects also to the mqtt broker.

Topics

The values will be pushed on:
SKWNCR_MQTT_TOPIC/SENSOR-NUMBER-WITH-LEADING-ZERO

Behavior

• the analog read interval equals the SKWNCR_TICK_RATE in milliseconds
• a value will be pushed, when it has been changed
• a value will be pushed again, if the last push is older then SKWNCR_VALUE_AGE in milliseconds
• the values can be shifted with a scale factor (SKWNCR_MQTT_TOPIC_SET_FACTOR), a float multiplier
• the values can be shifted with an offset, a float
• change factor, offset and interval at runtime per mqtt

Set factor, offset and interval at runtime

Publish a single number or float an the topic:
SKWNCR_MQTT_TOPIC/SENSOR-NUMBER-WITH-LEADING-ZERO/set/ACTION

ACTION can be:

factor
offset
interval

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have fun

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Hint

To have the 5th sensor for the zenith, use the only one analog input directly on the nodeMCU.

TODO

• store and read factor, offset and interval from eprom.

Why?

The reason for this tiny project is my own problem to know the light situation outside. In the evening hours the light comes flat from one side. The other sides of the house can be in a situation, that a turn on the light is necessary - but it isn't triggered. The lux dependency for our smart home lightning works crazy with only one lux sensor outside. And i have absolut keinen Bock drauf, to place lux sensors in any room.

How i use it?

• The device is located on the roof. No Shadow can reach the sensors.
• In the attic is the power and a low power DC wire is going up.
• The wifi access point is located directly in the attic.
• A mqtt broker (mosquitto) manages the messages.
• My own "transponder" node.js app writes all values from a given root topic in a influx database.
• The transponder create a average topic with the average of all four sensors.
• Grafana shows me the data.