Hi
I have a nodemcu esp8266 and double relay module that connected together for simple project that i have intent to develop it more .
I was connect two IN1,2 pins to d4 and d1 of nodemcu and vcc and gnd to 3.3v and gnd of nodemcu,
when i connect relay to nodemcu, its turned on and work with another power source that i connected to jd-vcc, but when i use that power source that i used for jd-vcc pin the relay does not turned on at all !
when i use jumper for jd-vcc and vcc pins and use nodemcu for turning on relay, relay turned on, but in case that use external power source with jumper mode the relay doesn't work at all .
After all testes that i did, it turns on that when i connected gnd of relay to nodemcu, the relay worked !!! ??? or something happened that i do not understand at all !
Sorry, don't have the time just now to detail this but that relay module does not require a common ground as such. It uses a common supply connection, which must be to the 5 V, not the 3.3 V.
How does this work without a ground from the Arduino? Presumably, the inputs go to an optoisolator, but how does the LED light up in the optoisolator without a ground? Even if the GPIO is active LOW, the Arduino ground needs to get back to the relay power supply ground to complete the circuit,
Paul__B:
Sorry, don't have the time just now to detail this but that relay module does not require a common ground as such. It uses a common supply connection, which must be to the 5 V, not the 3.3 V.
If you saw carefully first image tells that relay run with 3.3 v of esp board and relay's magnet runs with 5 v external power source .
SteveMann:
Post a schematic in CAD or a picture of a hand drawn circuit in jpg or png- ( and, please NOT a pretty Fritzing drawing).
Your images tell us practically nothing except that the relay needs a 5V power supply. How is the NodeMCU powered?
Please see all images carefully, that tell you all !
Nodemcu runs with usb from laptop(nothing connect to esp except this relay!)
I came with real images because this matter was so odd to me that I couldn't understand why!!
Paul__B:
Sorry, don't have the time just now to detail this but that relay module does not require a common ground as such. It uses a common supply connection, which must be to the 5 V, not the 3.3 V.
Thank you Paul, no need, perfectly capable of working it out for myself. The OP said it worked when s/he connected the grounds and seemed surprised by this. I applied the razor belonging to Mr Occam and concluded that a common ground was the problem and that the OP didn't understand about them.
SteveMann:
Post a schematic in CAD or a picture of a hand drawn circuit in jpg or png- ( and, please NOT a pretty Fritzing drawing).
Your images tell us practically nothing except that the relay needs a 5V power supply. How is the NodeMCU powered?
I added some hand draw, i hope help to solve the problem,
In schematics, 1 and 2 can turn relay on and relay works perfectly, 3 and 4 are can't turn relay on and relay not work at all.
I read it, and it's very useful, but is this really my problem?
Judging by the responses of others after me, probably not.
I added some hand draw, i hope help to solve the problem,
In schematics, 1 and 2 can turn relay on and relay works perfectly, 3 and 4 are can't turn relay on and relay not work at all.
Can you make it clear which ones you are referring to? Nothing you have attached is 1 or 2or 3 or 4. Please read How to post an image and follow the instructions (yes, I find them a pain too).
PerryBebbington:
Judging by the responses of others after me, probably not.Can you make it clear which ones you are referring to? Nothing you have attached is 1 or 2or 3 or 4. Please read How to post an image and follow the instructions (yes, I find them a pain too).
Edited first post.
My problem : why relay does not turn on with external power supply ? Every pics that relay is off is my problem.
