Qtr

[edgardito]

Hi,
I’ve just bought a few QTR sensors (digital ones) but I’m getting a hardtime using them.
I have my Osciloscope with me. I put 5V on VIN, GND on GND, and put my scope on OUT. I only get 0V on that pin.
I’m testing it with a white paper sheet with a piece of matte electrical tape on it, and I get nothing.
I used a Digital Camera, So I see the IR Diode working, but I get no reflection on the Photodiode. I tried putting and IR led in front of it, and nothing.
This happens with 2 sensors I got. I took another sensor, remove the Capacitor, and put a 47k resistor between OUT and VIN (generating a pullup of 47k22), and I get 5V on OUT, but no matter what I do with the sensor, (move it inside and out the black tape) I get no signal.

Is there any special surface where I have to use the sensor?

[Ben]

Hello.

It sounds like you might not be following the proper sequence for reading these sensors. Are you driving the output high to charge the capacitor? As the product page says:

The typical sequence for reading a sensor (with a microcontroller) is:

1. Set the I/O line to an output and drive it high
2. Allow at least 10 us for the 10 nF capacitor to charge
3. Make the I/O line an input (high impedance)
4. Measure the time for the capacitor to discharge by waiting for the I/O line to go low

- Ben

[edgardito]

Sorry, my bad.
I transform it into an Analogue version, but had a loose solder point. I tested it with the multimeter and realized that.
After that, works like a charm (in analogue mode).
My microcontroller has an A/D but I will use them as ON/OFF line detectors for a line following robot.

Thanks for the Help!