0
\$\begingroup\$

I'm interested in the following IR sensor breakout board with the QRE1113: https://www.sparkfun.com/products/9454

However, I would like to control the LED (on/off, PWM if possible). Should I disregard the breakout and see if I can get the QRE1113 seperately (hopefully nearby), or could I wire the LED to a pin on the Arduino (Nano)?

\$\endgroup\$
  • \$\begingroup\$ pololu.com/product/959 are doing it the same way. you output, charge up the cap (well discharge) then change to input and measure how long before the input state changes on the pin. you can always remove the other components on this board and be left with just the QRE1113 and/or remove it from this board and try it somewhere else. Id be curious to know what if anything you get with a pwm, would really need analog on the receiver to measure the intensity in that configuration? \$\endgroup\$ – old_timer Jun 20 '16 at 0:23
  • \$\begingroup\$ I could use the analog version as well, but the digital version seems nice to me as it doesn't rely on an ADC. If the LED is emitting less bright, wouldn't it just discharge less fast? I could take into account the brightness of the LED in my calculations. Either way, PWM is optional and not a requirement, I can do without. \$\endgroup\$ – LongLog Jun 20 '16 at 8:50
  • \$\begingroup\$ I guess my issue with the way they expect you to use this is that it relies on the switching point on the digital input, which is somewhere in no mans land and I wouldnt expect it to be the same place from chip to chip. So could you write one program that works with all of these? I guess you would need to experiment to see how accurate it is. Or maybe there is a calibration step required per unit. \$\endgroup\$ – old_timer Jun 20 '16 at 23:14
1
\$\begingroup\$

With that breakout board, you can do fairly slowly on and off by connecting the vcc pin of the breakout to an arduino pin. However the problem is with the capacitor in the schematic where if the vcc pulse is quick enough, voltage could actually seep through the capacitor to the vcc at its off state and possibly trigger the output. So basically you would want to remove that capacitor so you can use it for PWM. You could cut the connection to the capacitor:

enter image description here

Also wait for a couple of days before accepting this answer.

\$\endgroup\$
0
\$\begingroup\$

For other readers that are looking for a reflectance sensor with controllable LEDs; I found out that the QTR-8RC supports this. The only downside is that it contains 8 sensors. They have the ability to be split in 2 parts (2 and 6 sensors per part), but from what I understand the part with 2 sensors does not contain the LED control anymore by default.

Either way, it's something to consider.

https://www.pololu.com/product/961

It's not an ideal solution, so I won't mark it as answer yet.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.