Hello, I recently purchased some relays to turn on or off a lightbulb using an Arduino.
The relay doesn't seem to do its main function at all. Upon connecting the AC positive to the COM, the voltage outputted from the COM and the NC is 7 volts. The COM is receiving 120v.
I've tried multiple relays with no luck. I followed the diagram exactly as shown.
Update: I apologize for not being specific. I am using the Arduino R4 Wifi.
I don't have a picture or a diagram, but the connections are as follows:
Signal Trigger: Connected to active HIGH pin on Arduino 5v.
DC Negative: Connected to Arduino ground.
DC Positive: Connected to active HIGH pin on Arduino 5v.
COM: Connected to AC positive or hot wire 120v.
NO: Connected to Light Bulb.
Ground from wall: Connected to Light Bulb.
Question: Why is my relay outputting only 7 volts and not 120v when the relay is activated using the Signal Trigger?
So the 12V relay information you provided was incorrect. Please strive to provide correct information from the beginning.
So you're attempting to drive the relay coil, which nominally requires 71.4mA, with an Arduino output pin designed for no more than 20mA, or 40mA in a momentary pinch? Does that seem like it's going to work?
Do you mean neutral instead of ground?
Getting 7v where you were expecting 120v could mean you are measuring the voltage between mains neutral and mains ground (earth).
Consulting the readily available datasheets when selecting parts is fairly standard practice. So yes, I would have expected you to have that knowledge beforehand. I see I was mistaken. Good-bye.
You are playing with voltages that can kill you. You most DEFINITLY should know before you connect anything. The fact you told us you measured 7V from Common to NC is very telling. The NC contact is not used in this circuit. If I did a google on this I assure you I would get several 100's of thousands if not more.
From the examples you provided, it appears I was doing it correctly using COM and NO until I swapped them. However, another user mentioned the Arduino couldn't provide enough current.
Could it be the relay I'm using is not designed for the Arduino? Thank you.
Can you for the moment forget the Arduino and the relay module and simply get the 120v lightbulb and a conventional light switch working with your mains connection. Once that works then replace the light switch with the relay module and see if it still works.
I still have some difficulties to see where, with a 5 volts Arduino, you were able to measure 7 volts without some mains voltage leakage somewhere and this is definitely NOT harmless. You've already been warned about the dangers of working with mains voltages.
I am not aware of ANY MPU or MCU being able to drive a relay of that type. You will either need to switch to a solid state relay, or insert a driver circuit between the Arduino and relay.
On the board, signal trigger is 0V. At least to my relay board. I was trying to trigger it with 5V (or whatever the coil voltage is) and it did not work.
So on power supply voltage you should bring what the voltage of the coil is, and on the trigger input you should bring 0V to activate it. 5V or loose end keeps the relay OFF.
