I am just learning how to use an arduino and as a test project wanted to set up a wifi garage door controller. This seems pretty straight forward with lots of guides on the net where you use the arduino to trigger a relay. I have the code set up and using my multimeter I can see it is doing what I expect, triggering a HIGH voltage for a short time when I press the button on my webpage running on the arduino. However, when I connect my relay it is always on. I wonder whether this is because when the digital pin is set to low it still outputs a small voltage, and this is sufficient to trigger the relay already.
My set up is basic: TONGLING 5VDC relay board (JQC-3FF-S-Z) connected to an ESPduino.
- VCC on relay connected to 5V on arduino
- GND on relay connected to GND on arduino
- IN on relay connected to digital out on arduino
The signal on the IN pin on the relay is about 0.4V when the Arduino output is low.
The signal on the IN pin on the relay is about 5V when the arduino output is high.
As soon as I plug the relay in to the board it switches, even though the output pin is set low.
With a bit of googling, I found something (https://www.futurlec.com/Relays/JQC-3FF-05.shtml) that suggests the pick voltage is 3.8V and the dropout voltage is 0.5V.
My take on all this is that the low voltage is already high enough to switch the relay. Does this seem correct?
If so, is there any way to control the "LOW" voltage on the arduino so that it is closer to 0V?