This means that an LED has a specific polarity that must be applied to make it produce light. Failure to observe this polarity requirement could cause catastrophic damage to the LED.
This is because an LED has a relatively low value of reverse polarity voltage that is allowed normally about 5 volts.
Since an LED is essentially a diode, it has a maximum current value that cannot be exceeded for any period of time. With this in mind, we will explore the requirements for the limiting resistor that must be used in an LED circuit. Since LEDs are available in various colors, the required resistance value will vary depending on the color of the LED.
This is because the color of the LED is determined by the materials used to make it and these various materials have different voltage characteristics. The forward voltage value is the voltage required to cause the LED to light. Because of this variation, the value of resistor value will vary depending on what the LED color is.
The procedure is to choose a resistor value that will produce the correct amount of current to flow in the LED-based on this forward voltage value and the value of the Power supply that is powering the circuit.
Since automotive applications are one of the most popular uses for LEDs, I will go through an example of an LED lighting project that uses 12 volts as the power source. The important feature to note here is that the voltage value used in the calculation.
Since this is not a standard value I would use an ohm resistor. Already have an account? Login here. Choosing a resistor to work with an LED is fairly simple, but does require some knowledge of the LED and a small amount of maths. All other standard and bright LEDs will need a current limit resistor. When a diode is put in a circuit 0. Similarly LEDs have a voltage dropped across them know as the forward voltage, though this is different for every LED.
A proportion of the battery voltage is dropped across the LED the forward voltage and the rest of the voltage is dropped across the resistor. This is shown in the diagram top right. We can therefore write this as:. For example an ultra bright blue LED with a 9V battery has a forward voltage of 3. We have added a great tool to the Kitronik website that takes the strain out of calculating the current limit resistor. Simply select which LED you are using from a drop down list.
Enter the battery voltage and it will tell you what resistor to use. It even tells you what the colour bands will be on the resistor.
Click here to visit the calculator page. Learn more about the author read more ». That's because its hard to buy a ohm resistor and easy to buy a ohm one. Just use the nearest one you can easily find. To learn more about this magic formula read about Ohms Law.
Question 9 months ago on Step 3. Tip 1 year ago. Reply 1 year ago. This is a late answer, but will be helpful to others. This would need a diode ideally 4 of them, connected to make a full-bridge rectifier, to avoid flickering in addition to the large resistor.
A diode is like a 1-way valve--it prevents electricity from flowing "backwards", essentially making AC into DC. Reply 6 years ago on Introduction. Reply 7 years ago on Introduction. Reply 6 years ago. Question 2 years ago on Introduction. Answer 1 year ago. That is literally the exact question this Instructable answers. Read it, and you will have your answer!
Question 1 year ago. Hi, I am trying to rig up a single LED for an aircraft, 24 volt system, breakout box. It will be tested between 2 banana plug sockets. I need to have a LED light that will withstand higher current applications. And it needs to stay small, like for on top of a mini banana plug grounding plug. Any thoughts? Obviously it's 10 years too late for this guy, but maybe this will help a future reader.
Amperage doesn't work like that. As you probably know, the ampere is a unit of current. As such, it only applies in the context of a particular device. When you say the system is amps, this is referring to the maximum amount of current the source can supply.
It doesn't mean that is how much current a device connected to it has to use. The device connected will draw only the amount of current that it needs. The only thing one must be sure of is that the power source is rated to supply more amps than the device connected to it.
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