GPIO output voltage on ESP32 too low

[garyjamesstanton]

Hi all,

Firstly, thanks for all the hard work on this project - it is really cool.

Now on to my issue. I am using the library on an ESP32 and on the output pin the voltage is VERY low - as in less than 0.5v. I thought my ESP32 was maybe faulty at first, but it works just fine with a simple LED sketch using the same pin. The issue is that the output pin can barely drive a transistor so the maximum current I can get through the IR LED is only around 20mA. The LED can handle up to 100mA which would give it more range - but the output can't fully saturate the transistor to give me more current. Does anyone else have this pickle? Is it because of PWM?

[NiKiZe]

How do you measure the voltage?
When transmitting it is not on all the time, so unless you are using an oscilloscope you will not know the actual voltage.

What transistor are you using? Does it handle the frequency?

[crankyoldgit]

Sorry, I'm not an electrical engineer nor a electronics hardware guru. All I can suggest is maybe try a different NPN transistor?
E.g. https://github.com/crankyoldgit/IRremoteESP8266/wiki#ir-sending

[garyjamesstanton]

Thanks for the suggestion. I ordered a bunch more transistors to try including the one you suggested, they should arrive tomorrow. The one you suggested would work perfectly if the base was getting say 1mA which I suspect might be the case. I will post back how the new transistor goes.

[crankyoldgit]

If I under it correctly (and thats a big IF) transistors detects current in order to switch. (Base)

Where a FET/MOSFET uses voltage, so a FET may work of you have some handy

[garyjamesstanton]

Just a final update on this. I used the oscilloscope to measure instead, and everything is working as expected. Due to the PWM you just connect everything without any resistors and you get just about the correct amount of current to the IR LED - it can probably handle more actually, but the maximum I can get is just over 100mA which does the job. The origional question regarding the voltage - I was just wrong, and NiKiZe was 100% correct.

[NiKiZe]

Just to be clear here, you need a transistor, if not you risk burning your ESP (and probably won't get enough current) you should always use a resistor in series with the LED, and also to the transistor base. You could use for example use 5V or 9V to drive the LED for better range. It is also not uncommon to use multiple LEDs in series.