Hi everybody. I am using the analog variant of this part as a reflective encoder on a motor and it works fine as long as the reflective and non reflective surfaces are different enough in reflectivity regarding the IR spectrum. I am quite happy with it for now but I would like to have lower low levels to have a little more margin. I was thinking about a separate schmitt trigger but I dont want to add another component to my circuitry. Then I saw this igital variant. However, I am really curious on how this one is supposed to work. with only a capacitor connected to Vcc the output will never go high, and if you apply a pull up resistor upstream of the output after the 200ohm resistor you will have an analog variant again with worse performance because you will have extra voltage drop accross the 200 ohms. so I would really like to see some scope shots of this actually working "digitally". Maybe I am missing something, but I feel that this breakout board is redundant or even less performant than the analog one.

I am happy to hear other peoples opinion on this

On Arduino:

void setup () { pinMode(9, INPUT_PULLUP); }

void loop () { int val = digitalRead(9); }

I think that the 100 ohm is not enough to limit the LED current to the nominal 20mA specified in the component datasheet when powering the sensor with 5V.

This value is correct for a 3V3 supply, and has been obviously selected for this configuration of use, but it is definitely too low for 5V. The resulting current is (5 - 1.2) / 100 = 38mA. Even if under the absolute maximum (50mA) it is prejudicial to the LED lifetime.

Conclusion : either mention that the board is designed for a 3V3 usage (hence not for an Arduino) or change the resistor. Apart if your goal is to have customers buy more units after having fried their first batch ;)

How can I use these with a raspberry pi?

You use the 100-Omh resistor in the IR-LED circuit. Are You sure that the 50 mA current (with 5 volt source) isn't too large for the QRE1113? IMHO, QRE1113 is too hot.

hey sparkers--the schematic and eagle file links are broken. Just FYI

Here is an Arduino library for reading Pololu's version of this sensor. It should work for the Sparkfun version as well.

Hi.
I had a some problem that you.
pulsein is good, but for me it had a problem with timeout. When sensor get a black floor, pulsein didn't return any value and "void loop()" was freezed waiting for value.
Now I used the code below:
pinMode( pinLine, OUTPUT );
digitalWrite( pinLine, HIGH );
delayMicroseconds( 50 );
pinMode( pinLine, INPUT );
// long readLine = pulseIn( pinLine, HIGH, 1000000L ); // wait max for 1 second.
long readLine = 0;
while ( digitalRead( pinLine ) == HIGH ) {
readLine++;
if ( readLine == 15 ) { break; }
delay( 20 );
}
In my case, 1 = white and 15 = black.

Actually, I think that should be pulseIn(xxx, HIGH);

Looking at the schematic, I assume that you have to set the digital I/O line high to charge the cap, then flip it to input and time how long it stays high, e.g.
pinMode(xxx, OUTPUT);
digitalWrite(xxx, HIGH);
delayMicroseconds(50); // 220 ohm * 1e-9 farads * fudgefactor
pinMode(xxx, INPUT);
int reading = pulseIn(xxx, LOW);