calendar_today 17th May 2020

Solar panel and wires
Making light with light

I didn't listen/care in any of my lessons between the ages of the 13-16. I would get by paying little attention and score decent grades 'learning' the day before an exam.

I recall enjoying biology but not so much physics, thinking:

  • 'It's interesting, but *I* just don't get it'
  • 'This is way past me'
  • 'This won't apply to my life later'

Except now it does and there's no reason I can't re-learn (technically truly learn from basics).

I'm interested in building DIY essential tools to teach younger relatives/friends... except I can't sprout something if I'm not extremely confident at why everything happens.

I want to build kits where kids can build their own:

  • Solar-powered torch
  • Mobile phone
  • Washing machine
  • MRI machine one day (this will get fun)


Writing down a list of things I don't know and ticking each one as I go. In day 1 of this, we build a very easy solar light.

Following any manual is easy - anyone can build a jigsaw piece but I need to truly understand what happens here and why in the technical terms.

Are technical terms important? Not really. I loved Randall Munroe's 'How To'. It felt accessible and easy to digest. It didn't make me feel stupid (which younger self might have then chosen to retreat.

Terminology is useful to some degree in checking we all get what we mean, but also what happens if I want to build a manual and no one understands the English language? Note: Will use images for this largely.

Back to physics.

Can I expect kids to understand what the hell is going on as they build, if they don't understand the purpose of each component? Is this passive? I guess play/experimentation would be central here and naturally they would want to learn more. The aim is that they tear it apart and test around.

What I want to know:

  1. How can I use sunlight to turn my torch on?
  2. How can I store energy in my battery to turn my torch on at night, where this is no sun?

A circuit diagram:

Will insert scans


  • Solder gun / wire

    • to melt metal to form a connection between electronic components
  • Some wires

    • to form connections between components
  • 5.5v solar panel

    • light energy is converted into electrical energy
  • Diodes

    • passes current in one direction, blocks it in opposite direction (otherwise feeds battery votage to solar panel)
  • Diodes:

    • Reduces solar power loss due to shading
    • Electricity takes the path of less resistance
    • It's easier to go through the diode than the shaded cells
  • LEDs

    • light-emitting diodes to produce light
  • Resistors

    • controls flow of current (otherwise LEDs would be destroyed/overheated)
  • A switch

    • to turn light off/on
  • Old phone battery

    • to store energy so we can use the light, when there is no sunlight
Solar panel and wires
Solar panel and wires

Q1: How can I use (sun)light to turn my torch on?


What's happening?

  • Sunlight = electromagnetic radiation
  • Solar panels collect sunlight and turn it into direct current.
  • Solar panels are made from photovoltaics cells, which are made up of silicon semi-conductors (active layer - light hits electrons).
    • Electron metal conducting strip (around cells) electricity to power grid/whatever needs powering

EL15: (Explain Like I'm 5)

  • We can use the sun to power our torch
  • Solar panels are made from solar cells, which are made from silicon
  • Silicon can produce electricity when light hits it

This is a good video for kids

Why is this cool?

  • Renewable, as long as the sun shines, it will release energy
  • Plants do this, see Yale Scientific

Why not?

  • Solar power can be expensive and need for efficiency (solar modules convert approx 15% of energy, advancements in solar efficiency = cheaper solar energy)


  • Heat - will use alligator clips instead of soldering