Qtr

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?

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:

[quote]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
    [/quote]

- Ben

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!