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Low-cost Pyranometer and Raspberry Pi Pico – I

In the new Postdoctoral project, we are developing thin-film solar cell prototypes. However, some days ago I realize we will require the values of the solar irradiance W/m2 to determine the conversión efficiency \eta = (VocJscFF)/(1000 W/m2) of our cell prototypes. The problem here is we will require an AM1.5 Solar simulator or a pyranometer to calibrate the irradiance (W/m2) of a light source.

The possible solutions

In my opinion, there are two ways to have these solar irradiance values: a) Fabricate a low-cost pyranometer using silicon photodiodes; b) Calibrate a reference solar cell (Si, crystalline or monocrystalline) using a solar simulator. However, both alternatives require expensive devices like the AM1.5 solar simulator (Example: NEWPORT) and the Pyranometer (Kipp and Zonen).

Building the interface of a low-cost pyranometer

If we choose to fabricate the low-cost pyranometer we will have a way to measure direct and diffuse solar irradiance and we will be able to measure the conversion efficiency of our solar cells using sunlight. Moreover, if we build this device we can calibrate light sources (like Tungsten-Halogen lamps) to measure the interior J(V) curves using the µSMU measurement unit.


  1. Use Raspberry Pi pico as datalogger
  2. Build the Low-Cost pyranometer using a Si photodiode OPT101
  3. Calibrate the pyranometer prototype with a certified Pyranometer
  4. Program the data adquisition (introduce calibration curves or equations).
  5. Test it

Gallery – Getting the Raspberry Pi pico 2020

I recommend you to acquire this device in the official reseller stores, please find them in the official web page:

Raspberry Pi Pico 2020 – Puebla Mex

Basic Materials

We require the following basic materials to prepare the development board (Total cost 30 USD approx)

  • Solder iron
  • Soldering paste
  • Tin solder alloy
  • Pin Headers
  • Jumper Pack M-M
  • Breadboard
  • Raspberry Pi Pico
Basic components to test the Raspberry Pi Pico

Placing the headers

Place the headers in this position to work in the breadboard

Solde Headers

This is the first activity – Test your soldering skills (My advice is to buy one with the header solder if you have never solder)

Install on the Protoboard

Place the Raspberry Pi Pico in the breadboard, we are ready to connect it to the computer and test some basic programs using Micropython.


I choose the Raspberry Pi Pico due it its low cost ( 7 USD here in Mexico) and the possibility to use MycroPython to program the logic of our low-cost pyranometer. On the internet, I have seen the comparison between Arduino and Raspberry Pi Pico, and this device is highly recommended. Let’s see if they are right.

At this step, you don’t need to buy any electronic component or maybe just one resistance 330 ohms and one led to testing the Hello World of microcontrollers. Let’s test it in the next post.

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