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CoretechR / OMOTE

Open Source Remote Using ESP32 and LVGL
https://hackaday.io/project/191752
GNU General Public License v3.0
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R21 seems to have wrong value #32

Closed Salecorp closed 1 year ago

Salecorp commented 1 year ago

It seems like 3R3 is too low for protecting the IR LED. Is this a mistake or on purpose?

CoretechR commented 1 year ago

The small resistor is an intentional choice to get the best possible range out of the LED. Most 5mm IR LEDs are specified for a pulse current of around 1A. The LED is controlled by the IR library so it should be fine. But if a programming error occurs and the LED is powered on for more than a few milliseconds, it will get damaged. Some kind of protection circuit would be part of the next hardware revision.

Salecorp commented 1 year ago

I see, thank you for the clarification!

samdowrick commented 1 year ago

@CoretechR Here's an approach that utilizes the 555 timer for protection:

  1. Connect +3.3V Supply to 555 Timer: Connect the +3.3V supply to the power input of the 555 timer.

  2. Configure 555 Timer as One-Shot: Set up the 555 timer in monostable mode to generate a pulse when triggered.

  3. Trigger 555 Timer: Connect the trigger input of the 555 timer to the microcontroller's output. The microcontroller will trigger the 555 timer to start its timing cycle.

  4. Connect 555 Timer Output to Transistor Base: Connect the output of the 555 timer to the base of an NPN transistor (e.g., 2N2222 or similar).

  5. Connect Transistor Collector to +3.3V: Connect the collector of the transistor to the +3.3V supply.

  6. Connect Transistor Emitter to Q5 (DMG2301L): Connect the emitter of the transistor to the source pin (pin2) of the DMG2301L mosfet.

Rest of the circuit remains unchanged.

I can modify the schematic and upload an image to show this if it doesn't make sense.

CoretechR commented 1 year ago

@samdowrick Your idea makes perfect sense. I was actually considering using a resettable fuse or a big capacitor to limit the energy to the LED. But yours is a much more clever solution. Thank you! I've added it to the list of suggestions for a new hardware revision: https://github.com/CoretechR/OMOTE/discussions/24

CoretechR commented 1 year ago

Fixed in commit #33