My relay module is not working, i got 1 channel relay module, i've changed it to a newer one but it's still the same, maybe it's the wiring or power supply problem? When it is connected to my laptop, it shows red led turning on, but when i connect it to external power supply, nothing turns on, only the solenoid door lock moving(receive the power). does anyone know why it only light red led when connected to laptop and doesnt show anything when connected to external power supply?
Probably. Without a schematic, drawing or picture of the setup it's hard to tell. Also provide a link to the relay module.
Maybe a connections diagram and a link to the relay module you bought could help us to help you? 
Hi, @aestrate
Welcome to the forum.
Can you please post a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.
Thanks... Tom.... 
How did you connect relay module to laptop?
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