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Monitor your solar setup in your browser

TUTORIAL

Use an ESP8266 to let you keep an eye on energy generation from any device

Monitor your solar

setup in your browser

he amazing ESP8266-based boards

include all the hardware to connect

to a WiFi network and it can be

programmed to act as a web

server. Here we set one up to host a

website, which displays the sunshine

measurement on a simple dashboard. Any device,

computer or smartphone, on the same WiFi network

can view the data.

Light measurement is useful for assessing when to

switch on extra light or monitoring the performance of

a solar system. The TSL2561 light-integrated circuit is

a sophisticated device designed for making indoor light

measurements in lux units. Sunshine, or solar irradiance

is usually measured in W/m^2. Proper solar sensors can

be expensive, but this little unit can be modified to give

reasonable performance at a low price.

The integrated circuit contains two sensors: one

which responds to both visible and infrared light, and

another which responds to infrared light only. For

solar measurement, only the first sensor is needed,

especially if the measurements are used to evaluate

a PV system, as it responds to sunlight in a similar

manner to a PV panel.

The TSL2561 communicates using the I^2 C interface,

making it easy to connect to many small computer

boards such as the those using the ESP8266, and

of course the Arduino and Raspberry Pi. Modules

containing this chip and the necessary ancillary

components are widely available.

For this project, a NodeMCU V1.0, is used as the

host computer. The NodeMCU is easy to use as it

plugs into a USB port on the computer running the

Arduino IDE.

HARDWARE

I^2 C is a way of communicating over two data lines

known as SDA and SCL. The sketch assumes that

GPIO 0 (pin D3 on the NodeMCU) is the SDA line, and

GPIO 2 (pin D4) is used for the SCL line. The TSL2561

module also needs GND (0 V) and VCC (+3.3 V)

connections to operate.

To start with, the sensor and the NodeMCU are

mounted on a breadboard and the two connected with

jumper wires.

The maximum length depends on the connecting

cable capacitance, the clock speed, and the pull-up

resistors. In most cases a separation between the

T

Bill Grainger

Bill Grainger is a

physicist and design

engineer who loves

coding and having

computers interact

with the real world. He

works with wind energy

on all scales and enjoys

running, sea kayaking,

and mountaineering.

Above

Light sensor TSL2561

• back, front, and with
  PTFE filter in place