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hello there,

Where should I connected the LEDON pin to have the IR LEDS turn on? I am using the arduino mega 2560 micro-controller. From the guide for the QTR I understood that If I keep it disconnected, it means it will be pulled high and turned on. Am I missing something here.

also can someone please tell me if my understanding of this is correct:
when I turn the ledon pin and the IR leds are turned on, the qtr-8rc will start reading outputs and when I dont need any reading for example when my robot has figured the maze and just needs to get back, I can just turn off the IR leds and the QTR-8RC would just stop reading thus using less power.



The LEDON pin just controls the IR emitters. When it is high or disconnected, the IR emitters are on; when you drive the pin low, the IR emitters are off and the board draws significantly less current. If you are worried about your batteries draining prematurely, then you can try to decrease your current draw by turning the emitters off when you don’t need to read the sensors. However, messing with the emitters is just going to complicate your project, so I suggest you don’t worry about it until you have everything else figured out.

The Arduino library we provide for the QTR sensors can automatically control the emitter pin if you use the constructor to tell it what digital output you have connected to LEDON, or you can just use digitalWrite() to control it.

By the way, you almost certainly will still need line sensors to navigate a maze after you’ve solved it! Otherwise, it’s like trying to drive down the road with your eyes closed; no matter how well you know the route, you still need some kind of feedback to make sure you stay on it.

- Ben

I’m having the same problem, the LEDs aren’t working either.
I tried to disconnect the LEDON.
I also tried to connect it to a random pin, pin 11, and digitalWrite(11,HIGH);
I just use the example that come with the library, but none of them work.
I also checked with the multimeter, I’m getting voltage at LEDON


How have you verified that the LEDs aren’t working? How are you powering the sensor array? Could you post a picture of your setup?

- Ben

I attached a photo, basically, I just followed the example, ground to ground, Vcc to 5V, then connect sensors from digital pin 3 - 10
Following is a youtube video, the LEDs should be on like this, right?

hmm, maybe I’m asking the wrong question, basically, I just want the lights on, like the video I posted. Sorry if my question was wrong. :frowning:

The IR LEDs are clearly on in the picture you just posted (see how there’s a little purple light on each sensor?). Are you expecting to be able to see with the naked eye what the youtube video shows? Please keep in mind that the LEDs on the sensor emit infrared light that is not visible to the naked eye, but it is detectable by cameras without IR filters, like the one used to film the youtube video and the one you used to take your picture. Please see the second paragraph of section 7 of the QTR sensor array user’s guide for more information about this.

- Ben

heres the connections for the LEDON pin although mine is different it may work on urs.