People who are new to circuits frequently ask, "How many volts are required to power an LED?" "It's normally between 2 and 3 volts, depending on the color and kind of LED," explains Luz Rivas, an MIT Electrical Engineer grad. Student. But there is no single right answer because it depends on several factors such as how much current you want to drive through the LED, etc.
In general, if you want the LED to be bright enough to see, then about 20 milliamps is enough current for a pair of standard LEDs. That means each LED needs about 0.5 volt or less to light up. So, with two LEDs you need at least 1.0 volt, and if you want them to be very bright you'll need more like 2.5 volts or so.
However, people who want to use higher currents through their LEDs usually do so in order to reduce the size of the driver circuit needed to illuminate them. For example, if you want the LED to be very dim but still visible, you could use a current of 100 milliamperes, which requires only 0.05 volt to light up. This would be equivalent to having five LEDs instead of just one!
"It's normally between 2 and 3 volts, depending on the color and kind of LED," explains Luz Rivas, an MIT Electrical Engineer grad. To be certain, Luz advised that you look up the voltage. Some manufacturers specify that you should not connect their products directly to mains power, so make sure you know what type of connection they require.
The current flow through an LED is proportional to its voltage, so as long as the voltage is above its required level, it will work fine. However, if the voltage is too high, it can damage your LED array potentially causing permanent damage to your light fixture or lamp ballast.
Single LEDs emit light when electrons jump from a low energy state called the valence band to a higher energy state called the conduction band. This process requires energy, which is supplied by an electric current. The more current that flows through an LED, the faster it will emit electrons and the brighter it will get. However, excessive current can cause overheating and failure of the device.
Since electricity needs to be flowing in order for an LED to emit light, it is necessary that there is a path for current to follow. An LED array is a collection of many individual LEDs attached to a single piece of substrate. Current cannot be shared between LEDs unless another path is provided for it to go down.
Colored LEDs require roughly 1.9 volts, while white LEDs require approximately 3 volts. It is recommended to run an LED with a current and let the LED calculate the voltage required. For example, if an LED needs 5 volts to operate correctly, then connect it up like this: RESOURCE GRAPHIC A red LED will glow when electricity flows through it from positive to negative. So, first we need to find out how much current flows through the LED when it is on. We can do this by using our knowledge of Ohms law. Current flowing into an LED will be equal to current flowing out so we can just divide the total resistance seen by the LED by two. In this case, the total resistance including the contact resistance of around 0.6 ohms, is about 1.5 ohms so the LED should draw 1.5 amps.
Now that we know the current, we can work out the voltage by using Ohm's law again: Voltage across a resistor equals current times resistance so in this case it is 1.5 x 0.006 = 0.09 volts which is enough to turn on the LED.
As you can see, determining the voltage needed to drive an LED is very simple once you know the current requirement. The harder part is usually coming up with a way to provide this current.
Red LEDs have a voltage of roughly 1.6 volts while ultraviolet LEDs have a voltage of about 4.4 volts. It is critical to understand the right voltage since placing too much voltage across the diode might result in greater current than the LED can safely manage. LEDs are now available in two power levels: low and high. Low-power LEDs require only 3 to 5 milliamps with a voltage between 4.5 and 12 volts; high-power LEDs require up to 20 milliamps at less than 3 volts.
In general, higher voltages mean more light but also greater risk of damage to the LED. If you give an LED too much voltage, it will be damaged even though it may still work fine at lower currents. The voltage across an LED increases as current flows through it, so keeping voltage across an LED below its rated value is important for safe operation. A current-limiting resistor can be used to restrict how much current flows through an LED package. In this way, excessive voltage is prevented from building up inside the device while at the same time enough current is maintained to keep the LED illuminated brightly.
An LED lamp needs some type of driver circuit to regulate the current flowing through it. Since LEDs get dimmer as current flows through them, driver circuits should be designed with this fact in mind. Some types of drivers emit their own current rather than requiring a separate current source, so they can function as remote switches for other lights.
The LED current must be less than the maximum authorized by the manufacturer of your LED. The maximum current for ordinary 5mm diameter LEDs is usually 20mA, hence 10mA or 15mA are reasonable numbers for many circuits. For the computation, the current must be expressed in amps (A). Divide the current in mA by 1000 to convert it to A. Then multiply this number by 1.5 for red LEDs, 0.75 for green LEDs and 0.5 for blue LEDs.
For example, if you connect a 9V battery to an LED circuit using 16 ohms resistance, and the current through the LED is 1 amp, then the LED will be able to draw 900 milliamps from the battery. This exceeds the capacity of most batteries so the LED will not work properly. However, if the current through the LED is 500mA, then it will consume 300 milliamps from the battery and this is within its capacity.
In general, any LED that can be driven directly from a battery will have an operating current between 1/4 and full power of the LED, so you should be able to find information about the minimum battery voltage required for each type of LED bulb.
It is important to note that the actual current drawn by an LED depends on several factors such as temperature, so simply connecting up multiple LEDs will increase their total current demand. Also, different types of LEDs require different amounts of current to produce light with the same brightness.
You can have as many as you like as long as the overall amperage consumption of the LEDs does not exceed the breaker rating for that circuit. It is determined by the voltage available and the level of safety desired. Depending on the color, LEDs can 'drop' anywhere between 2 and 3 volts. Thus, if your circuit is 6 volts, you can only have 6 divided by 2 or 3 LEDs on it at a time.
For example, if you were to use six 575-lumen red LEDs on a 6-volt circuit, the total current would be about 1 amp. The maximum load capacity of a typical household circuit is 15 amps, so you would need to replace your breaker with a 20-amp version.
Here are some other things to consider before putting more than a few LEDs on a circuit:
The amount of electricity used by an LED varies depending on how much light it has to produce. More efficient LEDs use less power but cost more. Less efficient LEDs require more power and cost less per unit. Thus, the type of LED will determine how many you can have on a circuit without exceeding the circuit's limit.
Also, keep in mind that the more LEDs you have connected to one circuit, the lower the voltage will be across all of them. This is because the voltage dropped across each LED will be the same, no matter how many are connected together.