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Topic: Read Analog Voltage from external Source (Read 499 times) previous topic - next topic


May 20, 2017, 01:12 pm Last Edit: May 20, 2017, 02:08 pm by fwd82
Hello All, Hope you are doing well.
I did lot of Web and Desktop Programming and it's time to dive in Microcontrollers ;)
Arduino is something very sweet to me and I decided to use it.

What I have:
Plaining to buy :p
  • Arduino UNO
  • SIM900 Module.

What I want to accomplish:
I want to, read some voltage from outer source and then trigger function to send SMS from GSM Module.

What I mean by Outer/External source is, let suppose I have place my Arduino Circuit in home, and when I turn ON fan (just assume) or any other home applience so I will be getting Text Message on my Phone.
Remember Outer/External source is having 220V AC.

So I want to check if I have some voltage in my Analog Voltage Pin so I will be triggering the function for sending text message.

I know I can't use ~220v directly but I have first convert it into DC and then lower in between 0-5v.

I will be really great if you guide me if I am doing this right?
Let me know if I require extra stuff as well.

How can I figure our if Fan is now switched on? (Giving ~200v voltage to Arduino Pin and it reads it. )

Thank You very much.

I watch this YouTube video (LESSON 10: Reading Analog Voltages with Arduino) I get little idea from it, but mine context is different.


there are small sensor shields which are designed to measure the  AC current. these are what you need i guess.

here is one:



You don't want to "convert" 220 to 5vdc, you only need to "detect" the AC voltage, and it's the current you are looking for since it allows external detection. Any plug in cord will have the AC voltage/neutral on the conductors at all times. That doesn't change (unless it's a wall switched outlet). Any changes occur AFTER the on/off switch in the appliance, but the cord still has the same respective AC/neutral readings. What DOES change is the current used.
It's not a hobby if you're not having fun doing it. Step back and breathe


Jun 19, 2017, 10:59 pm Last Edit: Jun 19, 2017, 11:31 pm by fwd82
Hello @tinman13kup
Thank You very much for your anwer and advice. It is really helpful for me. :)

As you understand my idea, Can you please specify me the AC Current Detector suitable for my job?
1 - Sense AC Current (When I switch ON button)
2 - Arduino UNO will detect and
3 - Send Message via SIM900 module.
Can you please help me finding the devide and may be little show me a way to code how to detect AC Current from the AC device attached in Arduino UNO.
Thank You very much.

May be if you can help me choose from here:
Or show me online from any website?

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