I have two questions about the attached schematic from the Zumo-32U4-OLED robot.
Am I correct in assuming that the IN2 signal has a frequency of 38 kHz? If so, can I send NEC protocol codes to it, similar to those used in TV remote controls, to control home appliances?
Why so many 10uF capacitors? Do they increase the range, or are they needed for other purposes? Similar TV remote control circuits don’t have such capacitors.
Hello.
The Zumo 32U4’s receivers are designed to detect 38 kHz IR signals, so in normal proximity sensor operation, it generates modulated 38 kHz signals with pin 5 to control the emitters. It should be possible for you to generate arbitrary remote control codes and have the Zumo control other devices, although I don’t think that’s something we’ve tried. (The “RemoteControl” example from our Zumo 32U4 Arduino Library shows how to have the Zumo receive signals from an external remote control.)
The array of capacitors at the top of that part of schematic powers the emitters with a higher current (for higher brightness) right when they turn on, but reduces the current to a lower level within a few milliseconds to protect the LEDs. When the capacitors begin charging, the only thing limiting the LED current is the 22 ohm resistor. The current through the capacitors decreases as they charge, and when they are fully charged, all of the LED current has to pass through the parallel 100 ohm resistor (for a total series resistance of 122 ohms).
Brandon
