A diode is an electronic semiconductor device through which current can only flow in one direction. A light emitting diode (LED) is a device that lights up when current flows through it in the proper direction.
While early LEDs were low intensity and only produced red light, modern LEDs are available that release light across the visible spectrum. Because of this, they can be used for many different purposes. In order to have control over when the LED is on, you should wire it to a switch.
Note the rated amperage and voltage for the LED that you purchased.
Calculate the value of resistor that you will need for your circuit using the formula: (source voltage – LED voltage drop) / LED current amps = ohms. For example, using a 12-volt power source with an LED rated at 3.1 volts and 20 milliamps results in a resistor value of 445 ohms. Purchase a resistor with a value close to this value, rounding up as little as possible.
Solder your resistor to the positive wire of the LED; this is called the anode and is the longer of the two wires coming out of the LED.
Ensure the switch is set to the “Off” position. Connect the other side of the resistor to one terminal of the switch with a piece of copper wire. Solder the wire to both the switch and the resistor.
Solder a piece of copper wire between the other terminal of the switch and the positive side of the power supply; this side of the power supply will be marked with a “+” and will usually be the red terminal on a commercial power supply.
Place a third piece of wire between the negative side of the LED and power supply; the negative side is called the cathode and will be the shorter of the two leads coming out of the LED. Solder the wire to the LED and the power supply.
Flip the switch to the “On” position and ensure that the LED lights up properly.
Make sure you wire your LED with the anode and cathode in the proper positions or else the LED will not light up.
12-volt power source
Unclean.org: Beginner’s Introduction to LED Wiring
The Electronics Club: Light Emitting Diodes (LEDs)
How to Run LED Lights From a 12v Battery?
LED lights are a popular way of saving money in the home. They last for many hours, and a gently used light can last up to 25 years. Most LED lights are arranged so that they can run off of a 12v battery—in fact, 12v lights can cause a short when plugged directly into a socket, which usually have 110v current. This can be very dangerous, and so the best solution is to run these lights through a relay instead.
Step 1 – Decide Where to Put It
The first thing that needs to be done when connecting LEDs to a battery is to consider where they will go. Batteries operating lights on a high wall, for example, will need to have something supporting their weight. Unless you are installing these near an existing 12v battery supply, prepare to build a ledge, box, or other support. Leaving a battery to dangle will eventually cause connections to break.
Locate a nearby place to put the battery and on/off switch; then, measure the distance between where the lights are and where these will be. This is the length of wire necessary to connect the LEDs to the power supply.
Batteries and switches should be checked for faults before being wired to the LED home lighting system. This can be done by checking the current with a voltmeter, or by wiring both items to a lamp or device which is known to work.
Step 2 – Wire the LED to the Battery
Once the LEDs are in position, examine them and find the leads; the negative lead (or cathode), can be identified in one, or more than one, of these ways: it is the shorter lead, it is a flattened section on a round LED, or inside the LED, each lead is attached to a triangle-shaped node; the positive lead (or anode) is attached to a larger node. A diode test function meter will light up the LED when correctly applied. When it is lit, the black test lead will be attached to the cathode, and the red test lead will be attached to the anode.
When you are sure which lead goes to which, it is time to solder the wires to the 12v battery. The cathode goes into the ground—it can be soldered directly to the negative port of the 12v battery. The anode should be wired into the on/off switch, which is then wired into the positive port of the battery.
At this point, it is a good idea to check that the home lighting system works. Problems may include a blown fuse or damaged LED (easily done during wiring), or a loose connection somewhere between the lights and the battery. Correcting these problems is a simple task, and if the home lighting system is wired correctly, there should be no problems in using it for the foreseeable future.
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