#define LED_PIN 12įirst, and this is a best practice, we create a define for the pin number.
#Arduino led light table code
This code is very short and will just power on the LED on pin 12. This code will help us understand the setup and how digital pins work. Let’s say you just want to power on the LED when the Arduino program starts.
Arduino code to power on an LED Power on the LED with digitalWrite() OK, now that this is done, let’s go back to software. Any approximation that is above the minimum “safety” computation is fine. One thing to understand here: there’s no point in getting an exact resistor value. You could go as high as 1kOhm, for example if you want to add many LEDs, in order to reduce the overall current usage. In fact, you could also use a 330 Ohm resistor and it will work, just with a slightly lower brightness, because the current will be lower. 220 Ohm is more common, and it’s a higher value, so no problem. The thing is that, finding a 150 Ohm resistor is not that common. With those values, you’d need a resistor which is at least 150 Ohm, so you can make sure the current stays under 20mA. So, the computation for the resistor becomes (5V – 2V)/0.02A = 150 Ohm. This voltage drop is going to be different for different colors, but let’s approximate it to 2V. The thing is that, for LEDs, there is something more to take into account. So, if you want a max current of 0.02A, for a 5V voltage, you would need a 5V/0.02A = 250 Ohm resistor. If you modify the order you get: Resistance = Voltage / Current. With the Ohm’s law, you get the relation between resistance, voltage, and current: The max value can depend, but let’s agree on 20mA max, which is 0.02A.
#Arduino led light table software
This tutorial (and website) is more focused on software but I’ll make a quick parenthesis here to give you basic and simplified hardware explanation.īasically, you want to limit the current that goes through the LED, so you will avoid damaging it and also damaging the pin on the Arduino board. So, for the Arduino Uno, you get 20 possibilities. Note: you could have chosen any of the digital pins ranging from 0-13, and also any of the analog pins, which you can use as digital pins. Here we choose digital pin 12 on the Arduino Uno. Add a 220 Ohm resistor between this longer leg and a digital pin of the Arduino, using an additional colored wire (no red, no black) for convenience.Plug the longer leg of the LED to a different hole, on a different and independent line of the breadboard.Connect that leg to a GND pin of the Arduino, using a black cable if possible (convention for GND). Plug the shorter leg of the LED to a hole on the breadboard.Check the LED, you will see that one of the leg is shorter than the other one.First make sure that the Arduino is powered off (no USB cable plugged to anything).220 Ohm resistor (more info on the value later on).Test using only the built-in Arduino LED.
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