Hi, I have connected single relay module to arduino nano, relay works only when arduino is powered with USB. when i connect external power and usb then also it works, but when only external power is supplied relay does not work, here is schematic
Please post a sketch that illustrates the problem that you are having ?
Vin needs to be between 7V and 12V
You can supply exactly 5V to the Nano through the 5V pin ONLY if nothing is connected to VIN, or nothing will ever be connected to Vin or nothing is ever accidentally connected to Vin.
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You need to go back and do some basic tutorials on electronics. Also get the Arduino cookbook and read the sections that reference your project after skimming it. With how you have it connected I would be surprised if you have not toasted something. At that point you will know there is a control input to a relay and its controlling output.
My Crispy Critter Rules to save you future greef:
Rule #1. A Power Supply the Arduino is NOT!
Rule #2. Never Connect Anything Inductive to an Arduino!
Violating these rules tends to make crispy critters out of Arduinos.
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-Thanks let me try by giving voltage between 7-12v, but I have question, relay module just need signal to turn on off, so why dont it operate with pin out voltage which is 5v.
You said the only time it did not work was when you only used the external supply but you were not giving Vin enough voltage, so there was no output on the 5V pin.
Thanks,
I have googled it but could not find proper document, can anyone please point me to link which explain how voltage at pin is calculated for every micro controller when pin is set to HIGH or LOW?
I remember that if operation voltage is below 1/3 of then that will be considered as LOW to input pin and above 1/3(operation voltage) will be considered as HIGH pin.
e.g. for input pin what voltage range will be consider as pin HIGH and what voltage range is considered as pin LOW
and for output pin what will voltage when it set to HIGH and LOW
For the nano it's in the atmega328p data sheet. Find it at the Microchip.com site
Vih = Input High Voltage
Vil = Input Low Voltage
Voh = Output High Voltage
Vol = Output Low Voltage
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