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Trouble with ESP-01 + 1Ch 5V relay from LC Technology

PostPosted: Tue Jan 03, 2017 11:01 pm
by mk05406
Hi All,

I'm posting out of desperation trying to decipher the inner workings of a 5V relay module which comes bundled with an ESP-01 that I bought on AliExpess. This relay module is manufactured by LC Technology in China (http://www.chinalctech.com/index.php?_m ... &p_id=1204) They have some high-res photos of the module for the curious.

I tested the ESP-01 in isolation using both the stock AT firmware and NodeMCU and I can confirm it works perfectly fine (writing HIGH and LOW to GPIO0 & GPIO2 work as expected). I also tested the Songle 5VDC component in isolation by giving it a direct 5V feed and it clicks fine. However, when I assemble the ESP-01 on the module and toggle the state of the two GPIO ports, the relay does not click.

What would be a possible way to activate the relay other than toggling the state of the GPIO ports? Any combination (L/L, H/L, L/H, H/H) do not cause the relay to respond. I'm completely stumped and I'm desperate for some clues on how to troubleshoot this darned thing.

I have been unable to get any help from the seller or manufacturer with regards to how to actually control the relay component from the ESP-01 module.

Many thanks!

Re: Trouble with ESP-01 + 1Ch 5V relay from LC Technology

PostPosted: Wed Jan 04, 2017 10:31 pm
by mk05406
I received a response back from the manufacturer, seems the relay does not make use of the GPIO ports of the ESP at all. Rather, they use an on-board MCU (STC15F104W) @ 9600 baud to activate the relay.

Hope this helps someone in the future.

Re: Trouble with ESP-01 + 1Ch 5V relay from LC Technology

PostPosted: Sat Jan 07, 2017 2:18 pm
by jeffas
I don't think a GPIO pin from any ESP would provide either enough voltage or enough current to operate a 5V relay.

Re: Trouble with ESP-01 + 1Ch 5V relay from LC Technology

PostPosted: Sat Jan 07, 2017 7:03 pm
by Vishal dhayalan
Yes, i believe Jeffas is right, what I'd do is ground one terminal connected to the coil and connect the other via an NPN transistor with the base connected to the GPIO of the ESP, this allows the esp to activate the transistor and hence activate the relay!