I am trying to make a small humidity control system with the humidifier and dehumidifier being control by a relay (3pcs 2 Channel DC 5V Relay Module for R3 DSP ARM PIC AVR STM32 for Raspberry Pi with Optocoupler Low Level Trigger Expansion Board: Amazon.com: Industrial & Scientific).
I tested the relay with a power supply and with the Arduino on its own and they work just fine. Its when the Arduino has humidity sensor and LCD attached to it the relay doesn't work.
In both cases I have the relay being connected GND to GND, Vin to a digitalpin with output high and the control signal connected to a different digitalpin. This worked with just the relay being attached but when other electronics are attached those parts aren't powered and the relay stops working.
I suspect that the relay is exceeding the max current draw but I am confused as to why it would work with just the nano on its own. I would probably have to have a separate power source to power the coil on the relay but I wanted to try and avoid that if possible. Is there another route I could go?