How many LEDs can a 9V battery power?

9v can power 2 white/blue LEDs in series, or 3 red / (most) green / yellow. Each chain would need an appropriate resistor in series.

Do LEDs need resistors in series?

An LED (Light Emitting Diode) emits light when an electric current passes through it. The simplest circuit to power an LED is a voltage source with a resistor and an LED in series. If the voltage source is equal to the voltage drop of the LED, no resistor is required.

What voltage do LED lights run on?

Typically, the forward voltage of an LED is between 1.8 and 3.3 volts. It varies by the color of the LED. A red LED typically drops around 1.7 to 2.0 volts, but since both voltage drop and light frequency increase with band gap, a blue LED may drop around 3 to 3.3 volts.

How many LEDs can 5v power?

This is called kirchhoff’s voltage Law. So if you have a 5v power supply and each of your LEDs have a forward voltage drop of 2.4V then you can’t power more than two at a time.

Do I need a resistor to light up an led?

To light up an LED you need at the very minimum the LED itself and a power supply. From what I have read from other LED instructables wiring in a resistor is almost always a good idea. LEDs – I basically just reached into the drawer at Radioshack and pulled out anything that wasn’t more than $1 or $2 per LED. I got:

How do you wire more than one led to a power supply?

When it comes to wiring more than one LED to a power supply there are two options. The first option is to wire them in series and the second is to wire them in parallel. To see an in depth explanation about the difference between series and parallel check out this page.

How can I increase the voltage of my LED lights?

So ideally you would like the voltage of the LED to match the voltage of your power supply, or even be slightly less. To do this you can do a couple of things: change your power supply voltage, change the LED your using, or you can use a resistor that allows you use a higher voltage power supply with a lower voltage LED.

How to calculate the series resistor for LED lights?

However to ensure that the 2 LED string consumed uniform current just like the remaining 3 LED strings, we calculate the series resistor accordingly. In the formula we simply change the total forward voltage as show below: R = (supply voltage VS – LED forward voltage VF) / LED current = 12 – (2 x 3) / 0.02 = 300 ohms