ESP8266 Community Forum

I have a relay shield that was made for arduino, it works just fine on my arduino, but when I try to drive it from a digital pin on a NodeMCU board, it always stays high. Any idea what's up? I have another shield that is working just fine on it, but two of them don't. I was able to create my own circuit with a 2n2222 that worked fine also.

Could you give some specifics about the relay shield?,

My best guess is that the relay need to be controlled with atleas 5V, while the ESP provides 3v3 Volt that one works is just luck i suppose. What you could do is add a transistor which switches the 5v of the relay,