You've no doubt gazed, starry eyed, at props and costumes that incorporated LEDs. They add that special something to them, that extra bit of magic. But it can also be very intimidating. The fear of something going wrong paralyzing you; Electricity, fabric and foam seems like a terrible combo. To top it all off this can be a heavy and confusing topic. So, since I'm dipping my toes into this myself, I aim to try and demystify this subject as best I can!
The hardest thing about learning a new hobby is trying to translate the lingo used in the instructions. Once you understand the terminology and abbreviations for things it'll be easier for you to dive right in.
Light Emitting Diode (LED): The tiny lightbulb we'll be talking about in this article.
Voltage (V): is the pressure from a power source that pushes an electrical current through a circuit or conductive loop.
Voltage is measured in Volts (V)
Amperage (mA): The measurement unit of an electrical current.
Also known as the Forward Voltage of an LED
Alternating Current (AC): a current that changes magnitude and polarity at regular intervals.
Resistance: The opposition to the flow of electrical current through a circuit.
Resistance is measured in Ohms
Impedance: Opposition to the flow of AC current due to components that could be resistant to electrical currents.
Voltage Drop: the amount of voltage loss that occurs throughout a circuit due to the impedance of a circuit.
Resistors: A tiny component wired into an electrical circuit to help reduce the current to a precise amount to prevent burnouts.
If you've ever dug into this subject before you may have run across numerous equations and spreadsheets for voltage drop and resistor capacity among other things. These equations help you calculate the voltage needed to run your LED project, which resistor's you need to use and what kind of wiring you may need.
Knowing what voltage your LEDs require is important. If you use a power source that is too strong for your LEDs, it will cause it to burnout. Too weak of a power source and you run the risk of some, if not all, of your LEDs not working at all.
These equations and standards come from Kirchoff's Circuit Law. Lucky for us, There's only a few take away's from these laws that pertain to us right now:
The resistor voltage must be equal to the voltage source (your battery), minus the sum of the voltage drops of the LEDs.
If your Voltage source is equal to your LEDs voltage drop you will not require a resistor.
If all of that is too much fiddling with numbers for you (Honestly it is for me so no judgement here) then you're in luck! Most small scale LED projects will only require a 330 Ohms balast resistor. And if you're tackling a larger project, there are a ton of online calculators to help you figure out what kind of resistor you need, if any at all. You can also install the AdaFruit App.
Okay, now that we've slogged through all the dry heavy info, and you're still with me on this, we get to go into the fun stuff. We get to start talking about materials, what to use and where to get your supplies.
Electrical wiring comes in many different sizes and capacities. The gauges are measured in the American Wire Gauge (AWG) and go from 12AWG (the largest gauge) to 30AWG (The smallest gauge). The wire will list it's rated voltage on the spool. The rated voltage is the maximum amount of voltage the wiring can handle safely.
I'm personally a fan of the wire in the 20-22AWG area, not only does it match up size wise to most wires off of battery holders, the type I use is easy to strip and has a voltage rating of 600 volts.
There are a a few different types of LEDs, but as you've no doubt noticed, just typing in LED lights into amazon will result in more flashlights and lightbulbs than the tiny diodes you were hoping to find.
Knowing what kinds of diodes you're looking for can help narrow down your search quite a bit. Since this is just intro to LEDs I will not be going into Surface Mount Diodes (SMD) so we will only be looking into two overarching types of diodes:
Micro LEDs: About as small as a pinhead and powerful
Usually the wires are pre-insulated with exposed ends for soldering.
Some brands distinguish the wires by color. In these cases the copper, or red wire, is usually the positive, and the silver is usually the negative.
About the size of a matchstick head (5mm)
Has two pins extending from the bulb, one longer than the other. The long pin is usually the positive side.
There are a lot of varieties of LEDs in both of these categories to include LEDs with built in resistors (handy and magical). The different colors all have different voltages as seen by the chart below.
When using multiple LEDs its crucial that you add all of it together to determine how large of a power source you will need.
The easiest way to light up an LED is to Simply connect an LED directly to a coin cell battery. Since the coin cell battery cannot provide enough of a current to damage the LED you can tape the legs of the LED directly to the battery. Then, as the name suggests, you can just throw it into a thing and make it glow!
You're probably nervous about soldering, it sounds fancy and you've likely seen people in movies using magnifying glasses in order to see what they're doing. Relax, it's not that intense I promise.
Some equipment you'll need is:
Soldering Iron: This usually comes with solder to get you started.
A soldering station: A nice placeholder for your Iron and cleaning materials, not necessary but very helpful
A helping hand: This is also optional but, is as the name suggests, very helpful. You can make your own by making cuts in a plastic cup to hold your wires and LEDs.
Soldering, simply put, is melting a metallic alloy called solder to your wiring, ensuring they're connected firmly and the electricity will flow through uninhibited. It may take a little practice to be able to neatly solder the wires to one another but if you follow the below steps you should be able to create a secure connection!
Clean the soldering Iron tip by wetting it and using a copper Brillo pad. Give it a few minutes to heat up fully.
While you're letting your iron heat, remove the plastic insulation from both ends of the wire. You can do this with a wire stripper, carefully with wire cutters or with your finger nails. If the wires are stranded, twist the strands together so you won't have any "fly-aways".
Hold your soldering iron to the wire for three to four seconds.
Keep the iron in place on the wire, this is where that helping hand comes into play, and touch the solder to the wire, allowing it to fully coat the end of the wire. Do this with both wire ends. (This process is called tinning.)
Hold the two tinned wires on top of each other and then apply the soldering iron to both wires in order to melt the solder together.
Allow the wire ends to cool for a few seconds and use electrical tape to cover the connection.
There you go, soldering made easy (I hope)! Now we can move onto how to form your circuits.
Installing Your Resistor
Resistors do not have a polarity! And as such can be installed on either side of the circuit, or even directly joined to the LED leg.
Handily, some coin cell battery packs have switches built in this makes your wiring of circuits very easy. Simply solder your LED to the battery pack, insert a resistor if necessary, insulate the exposed wire with Electrical tape or shrink wrap and Voila~ you have a successful circuit.
Insulating the exposed portions of the wire, or the portion's you've soldered, is key! If the negative and positive wires touch, it will short out your circuit.
A series circuit, simplified, is a line of "Daisy chained" LEDs, soldering + and - legs together as seen in the below examples, to complete a circuit. Connecting multiple LEDs in a series is slightly more energy efficient than series-parallel circuits and, if they are the same color, can share one resistor for the chain.
If you are daisy chaining multiple colors in a series, each color must have its own resistor, and you will need to use wiring to connect all the positive legs to one another and then all the negative legs to one another. (As seen below)
Remember to take the voltage of all the combined LEDs into account when choosing your power source and resistor.
LEDs wired parallel to each other have a lot more rules than the simpler series method detailed above.
LEDs in a parallel require separate resistors for each chain of diodes.
Each chain, or string, of diodes must contain LEDs of the same voltage.
Done incorrectly, you'll notice that the lower Voltage lights will light up and the higher voltage lights will not. Make sure you calculate for resistors properly and use a large enough battery to power all of your LEDs.
A switch is inserted into a circuit and gives the user the ability to interrupt the flow of electricity. It can be installed into either the negative or the positive side of the circuit.
There are two types of switches:
Momentary: Only remain active as long as they're actuated (held down). It's mostly buttons that will will fall under this category.
Maintained: Stay in one state, on or off, until you push it to a new state. These are where you would categorize your switches. There are some buttons that can fall into this category as well.
Some switches and buttons have two prongs, some have three. If you are working with one of the three pronged switches, you will need to utilize the inside prong and one of the outer prongs in order for the switch to do it's job.
Tips and Tricks:
Don't blow on your soldered joint! This will make it brittle. Let it cool naturally.
Inline splice is best for wearable projects. Avoid the pigtail splice (Joining the wires side by side) for wearable projects if at all possible.
Tin your tips! Tin the tips of your wires and your oxidized or blackened soldering iron! this helps with heat transference from the soldering iron to the wires.
Other LED Blogs:
Like this kind of content and want to see more?
How do resistors work? What's inside a resistor? (2019, July 22). https://www.explainthatstuff.com/resistors.html
Resistorwp. (n.d.). Resistor for LED " Resistor Guide. http://www.resistorguide.com/resistor-for-led
Light-Emitting Diodes (LEDs). (n.d).
How to Solder: A complete Beginners Guide. (2017, April 26). How To Solder: A Complete Beginners Guide. https://www.makerspaces.com/how-to-solder/