Nifty Hobby Projects for LEDs and Solar

Written by team-member Mark Ridley

I’ve completed nine of the how-to modules with more to follow as I work on them. The one I was working on next was a Solar NiMH Battery Charger module, due out as soon as I get the delivery of semiconductors I’m waiting on.
So, in the meantime, I’ve done one for a bedside lamp that uses rechargeable NiMH batteries.

As I found out while researching for these projects, there’s a lot of out-of-date and some simply wrong information out there. Rest easy, though. I’ve built each of these projects over the last few weeks so the components listed are all currently available and the circuits work safely.

3 strings of LEDs with ping pong balls as light diffusers

These projects all came about because of a Chinese-written English description. I wanted 100 flashing LEDs and that’s how they were described. But they weren’t flashing, they were colour-changing – not at all what I was after. Well, having received them, I thought I’d better find a use for them!

So, read on for a list of the hobby LED / Solar projects that you can build, too. All instructions, tips, explanations, circuits and component lists are covered – and have all been built and tested by me – so you can build the one(s) that take your fancy with confidence.

Who are these projects aimed at?

Anyone with a passing interest in electronic hobby projects including kids aged 12 years and up.

Why the age limit? It’s because the projects involve a soldering iron and sometimes a drill as well. I would recommend some form of supervision for the lower end of the age range as a sensible safety precaution.

If you don’t want them using an electric drill, a hand drill is fine because holes only need to be put in thin ABS plastic.

Mix ‘n match

I’ve designed these as modular projects so they can be connected together to suit what you want to achieve. Ideas for their use include Christmas decorations, party lights, porch lights, nightlights and relaxation room lights. I’m sure you’ll come up with your own ideas as well!

Typical Outdoors Set-ups

It’s never a good idea to fully discharge your batteries because they’ll last more charge / discharge cycles if you don’t. So I recommend always using the Timer Delay Off Switch so you’ll hopefully leave some charge in the battery.

sketch showing ways to connect modules for outdoor use
Typical set-ups for using outdoors

Typical Indoors set-up

sketch showing ways to connect modules for indoor use
Typical set-up for using indoors

List of Modules

  1. Stand-alone Memory Aid project (Done)
  2. Dark-activated switch for use indoors (Done)
  3. String of 5 colour-changing LEDs using ping pong balls to diffuse each LED’s light (Done)
  4. Fibre optic display using 5 colour-changing LEDs (Done)
  5. Mini Sparkles fibre optic string using 10 colour-changing LEDs (Done)
  6. Solar panel Lithium Ion battery charger with over-charge protection and dark-activated power output (uses TP4056 board with in-built protection) (Done)
  7. Timer-delay Off Switch (switchable between 4 and 8 hours) for when you want your LED strings and / or LED Fibre Optics modules to switch off during the night. This will conserve your battery power during the times when there’s not enough sun to fully recharge it (Done)
  8. Solar panel NiMH battery charger (3 batteries in series) and dark-activated power output. It uses a maximum trickle-charge current of less than C/10 to protect the batteries.
  9. Night-time Porch Light (Done)

Stand-alone Memory Aid project

To help older people whose memory is starting to fail – a flashing LED in a PP3 battery box with attached paperclip for reminder notes.

a photo showing the memory aid flasher with the blue LED aglow and a note attached to the paperclip
memory flasher

Building this module involves mainly hands-on craft skills with a small amount of soldering.

Link to project: Nifty Flasher Memory Aid

Dark-activated Switch

This is designed for indoor use and so isn’t weather-proof.

The dark-activated switch allows you to power a number of colour-changing LED displays, delivering up to a safe maximum of around 2 or 3 amps. This is limited by

  • the power source supplying the module
  • the current capacity of the diode(s), if you added any, in the power source feed into the dark-activated switch (usually 1 amp)
  • the ability of the output semiconductor (a MOSFET) to dissipate heat within the confines of the battery box used

It uses a phototransistor sensor to detect falling light levels and, when it’s dark enough, whatever it’s powering will be switched off. The battery box switch is used to disable the sensor so that the power is permanently on.

Link to project: Nifty Dark-activated Switch

String of 5 colour-changing LEDs

Designed for outdoors or indoors – great for your garden, patio or gazebo or decoration for your Christmas tree, a wreath or your porch.

The strings use ping pong balls as light diffusers – and they look really great!

a completed 5 Colour-changing LED String

Link to project: 5 LED String

Fibre Optic Display

Designed for indoors – great for night lights, Christmas decoration and relaxation rooms – or just to add an accent to your living space.

Building this module involves mainly hands-on craft skills with a small amount of soldering.

The fibre optic display uses 5 colour-changing LEDs, each with their own bundle of 30 fibres, to give an incredibly pretty display and as the colours slowly change, it gives a subtle sense of movement.

Having them in pairs is a great way to give visual balance so, once you’ve mastered making the first one, crack on and make more. One dark-activated switch can easily power and control 6 of them, so don’t hold back!

Link to project: Fibre optic display

Mini Sparkles Colour-changing LED Fibre Optic String

Designed for indoors – great for shelf lighting, night lights and Christmas tree decoration – or just to add an accent to your living space.

photo of the mini sparkles LED string all lit up and looking pretty
mini sparkles LED string looking pretty

Again, this uses colour-changing LEDs and the short lengths of fibre give a really great sparkling effect.

It’s a bit of a tight fit but is a great use of DC power plugs and panel sockets to give a fun project with minimum soldering that’s well within the capability of those at the younger end of the 12+ age range.

Link to project: Mini Sparkles Colour-changing LED Fibre Optic String

Solar Lithium Ion Battery Charger

pictorial schematic of solar Lithium Ion battery charger

This module charges the battery during the day and switches on the connected LED display module(s) at dusk. It’ll happily power two strings of 5 colour-changing LEDs from dusk to dawn.

You can use it with the (tbc) Timer-delay Off Switch module to conserve battery power during the night – great for spells of cloudy weather (we’re in the UK after all!) or during the winter months.

Link to project: Solar Lithium Ion Battery Charger

Timer-delay Off Switch

Conserve your battery’s juice by switching off whatever it’s powering after a switchable time delay.

photo of the Timer-delay Off Switch
the Timer-delay Off Switch before closing up and sealing the box

Attach a magnet to get 5 hours before it switches off or don’t use a magnet and it’ll switch off its load after 8 hours.

The key components here are a reed switch that closes when you bring a magnet near and a steel washer for the magnet to cling to.

Link to project: Timer-delay Off Switch

4-LED Porch Light

…or you can use more LEDs depending on how you intend to power it.

This is a great starter project for kids at the lower end of the 12+ range with only a little soldering

shown here as a simple module with a power-in lead

The LEDs used are diffused, high powered white ones to give a glow rather than directional light. If you can find an enclosure that is semi-opaque, you’ll get a more even diffuse glow.

Link to project: Porch Light

Tools in common you’ll need for these projects

See the individual project modules for any additional tools they need.

  • 18 Watt soldering iron, 25 Watts at a push
  • Desoldering pump / solder wick – ‘cuz we all make mistakes!
  • “Helping Hand” – invaluable aid while soldering or gluing
  • Wire strippers covering 26 to 16 AWG
  • Side cutters
  • Small snipe-nose / needle-nose pliers
  • Set of watchmaker-style screwdrivers (cross and flat-bladed) – also useful for poking and prodding
  • Glue gun for fixing components and wires in tight spaces to prevent short circuits
  • Small drill with drill bits increasing in size to 6mm diameter


Info / How-to

Learn the basics

…and find other projects to build at

UK Suppliers / supply links

Here’s a list of the cheapest / best supplier pages for most of the bits and pieces needed for the Nifty projects. I’ve grouped them in such a way as to minimise delivery costs.

They are all from the UK unless they are significantly cheaper or there’s really no alternative.

For the FQP27P06 P-Channel MOSFET and IRLB8721 N-Channel MOSFET – I’m working on a cheap source for small quantities. Watch this space

Other projects in the Nifty Hobby Projects for LEDs series:

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