Looking to spice up your Halloween decorations this year? Learn how to make LED eyes for less than $5 with this beginner electronic project.
Here’s what they look like in the dark:
What you need
- 2 x 5mm red LEDs ($5.27/50) [ Великобритания ]
- 1 x 27 ohm resistor ($6.16/100)
- 3 x AA batteries
- 1 x SPDT switch ($11.78/20) [ Великобритания ]
- Assorted heat shrink tubing ($6.29/set) [ Великобритания ]
- Assorted 7/0.2 jumper wires ($8.99/set) [ Великобритания ]
Total cost: $44.44. It’s not even close to $5!
You will need some basic tools for this project. You can get by with tape and cable ties, but that won’t make a very secure connection.
- wire cutters
- Wire stripper
- solder sucker
- soldering iron
- «Helping Hands» (UK)
This is a simple scheme — do not be afraid of this. Three AA batteries connected successively (one by one). This increases the voltage to 4.5V (each AA battery is 1.5V). Parallel connecting the batteries would increase the current — this is not necessary, since the minimum voltage required to light a single LED is about 1.8-2.4 V, which can provide a little more than one battery.
The resistor is needed to limit the current going to the LEDs. Never connect an LED directly to a power source, it will usually burn out. There is a definite formula for calculating the required resistor (although LEDs often tolerate a small difference). This site is great for calculating what you need. If you want to use more LEDs or a different battery setting, enter the following details:
- Supply voltage (in this case 4.5 V from 3 x 1.5 V batteries)
- LED voltage drop — typically between 1.8V and 2.4V
- Required LED Current — Typically 20mA
- Number of connected LEDs
The retail stores where you buy LEDs often list these specifications. click, to calculate, to get the resistor value you need.
Finally, the switch simply turns on and turns off chain. You should not use this, although it will save battery life when not in use.
First, make sure there are no batteries in the battery holders! It can be dangerous to heat the batteries too much. Solder the battery holders together, moving from red to black to red . You should have a red and black cable (one at each end of your chain) «free» for the rest of the chain.