LED are *REALLY* Dim

[howie]

We're assembling our PI bot and the LEDs are so dim such that we almost didn't notice them working...

[jasea]

Hi howie,
Welcome to the Pi-Bot forum.
First a very simple question, assuming that you have checked and double checked that your wireing is correct, can you check the switch that is alongside the power socket, it is two positions labled labled 3V3 and 5V. Make sure that it is in the 5V position.

Regards

John

[howie]

Yep. Definitely in 5V position... We will need to double check the wiring. Only play with it once in a while... Will update when we try again.

[jasea]

Hi again howie,
    The LED circuit is very simple + 5V connected to the LED connected to a resistor connected to Ground.
    So the problems can be
    1. the + 5V is low, but you have said that your sonic Sensor ia now working so + 5V should be OK. but see below
    2. The resistor to too large, this will cause too much voltage to be dropped across it and not leave enough for the LED. The resistors should be 330 ohm that is orange, orange, brown if they are three band coded or orange, orange, black, black if they are four band coded.  
    3. There is a wiring problem and you are not starting out from a + 5V pin or returning to aGnd pin.


You can check your board voltage by running a blink LED pgm such as that below, just change pin 13 reference to the PIN you want to test, put a Volt meter from that Pin to GND, run the pgm and you will see the voltage go from + 5V to 0 and back again every three seconds.

Please let us know how you get on.


// the setup function runs once when you press reset or power the board
void setup() {
 // initialize digital pin 13 as an output.
 pinMode(13, OUTPUT);             // change to a digital pin number you can get at
}

// the loop function runs over and over again forever
void loop() {
 digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)        // change to a digital pin number you can get at
 delay(3000);              // wait for three seconds
 digitalWrite(13, LOW);    // turn the LED off by making the voltage LOW         // change to a digital pin number you can get at
 delay(3000);              // wait for three seconds
}