Make a Tiny Long-lasting LED Torch




Introduction: Make a Tiny Long-lasting LED Torch

About: Software/hardware enthusiast, hacker, maker, father, husband, vim devotee, git lover, Node.js afficionado, SA. Currently working on: @timecounts, @MakeSoton

This project is to make a tiny torch that offers comfort in the night and a limited amount of illumination. Red is recommended since it affects sleep the least (and works for longest). A resistor is used to reduce the brightness of the LED, thereby increasing the battery life.

You will need:

  • An LED (preferably red)
  • A resistor (around 150 ohms works, but your taste for battery life versus brightness will dictate this)
  • Side cutter
  • Soldering iron
  • Solder
  • CR2032 or similar 3V Lithium cell battery
  • Optional: flux

Many of these things will be available at your local Makerspace, such as Southampton Makerspace, UK.

Step 1: Cut One Leg of the LED to Under 1cm

Before you do any cutting you might light to experiment with different values of resistor. If you want a really bright light then don't use any resistor at all - the internal resistance of the CR2032 will be sufficient to prevent a normal 20mA LED from burning out. Inserting a resistor will reduce the brightness of the LED but increase it's effective lifespan.

Step 2: Cut One Side of the Resistor to Match

Step 3: Solder the Resistor to the LED

Helping hands can help you to hold the LED and resistor steady as you solder them. If you're using lead-free solder then we recommend one with high silver (Ag) content.

Step 4: Insert Battery and Secure

Insert the CR2032 (or similar) battery between the "legs" of the LED/resistor. The battery should not foul the resistor, and if the legs are too long they should be trimmed to prevent shorts.

If the LED does not light when you first insert the battery between the legs then turn the battery the other way and try again - you will not damage the LED putting the battery the wrong way around.

I secured the battery to the LED legs using sticky tape; do not attempt to solder the battery as it may explode. When wrapping the battery you want to ensure that it is fully contained so as to avoid a short.

Step 5: Place Somewhere Safe

I place it on the windowsill for my son and his fear of the dark has completely evaporated; he can also easily get it if he needs to get up in the night.

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    3 Discussions


    Reply 5 years ago on Introduction

    In a pitch black room you could still see the LED glowing over a week later; however it was significantly dimmer than at the start.