ESP8266 Community Forum

- Mon Jan 05, 2015 2:00 pm #6380 Is that specific for the esp8266 or a generel value for any transistor ?

So I tried with a 1k Ohm resisitor, but still no luck. I added a pull down resisitor of 10k Ohm, but that didn't change anything.

Any further ideas ?

- Mon Jan 05, 2015 2:09 pm #6381 It is specific for GPIO maximal output current. I would recommend you definitely digital MOSFET, foe example IRLML2502 with resistor about 2k2 from gate to souce (for GPIO2 only). And antiparalel diode bypass for relay.

- Mon Jan 05, 2015 2:26 pm #6384 I already have the diode in place, but I din't add it to the schematic, because it doesn't belong to my problem.

So is there no way incorporating the transistor for testing purposes ? (I don't have amosfet lying around)
For my pcb, I will switch to a mosfet instead.

- Mon Jan 05, 2015 2:38 pm #6386 A 100ohm base resistor is definitively shorting the GPIO. It can even damage your ESP.
Any kind of transistor based driver should have at least 1K, but 4K7 is much more normal.
Then, if the transistor can't provide enough current to the relay, simply add a second stage transistor, making a Darlington assembly.
(or, of course use a MOSFET, which draw very low current thru it's gate, the GPIO will see it as it was a 1Meg resistor)