Monitoring mains voltage? - Solved

Projects General Guidance
1

Hello, I'm also working on monitoring my mains voltage using the Cheap blue CT clamps. I'm running into a few issues on my end trying to understand a few things. I tried to follow this guide. I know it is outdated and everything I searched online pointed me to it https://openenergymonitor.github.io/forum-archive/node/58.html. On there it has a power adapter a ac to ac adapter. I don't have any all mine are from ac to dc. Do I really need that adapter or is there a way around that?

the second question is the voltage divider it is brings the voltage down from 5v to 3.3, Why is that? I'm trying to understand that. Any advice would be great. I'm not looking for accuracy. I'm just trying to get it at the moment to see if it is working or not then work on the accuracy part.

Joseph

2

Knowing the mains voltage only is not really much use as it can vary substantially.

The CT clamps measures the current through whatever it's clamped around. It's output is an analog signal that is passed to the Arduino.

The ac -> ac transformer isolates you from the mains voltage and gives a relative voltage reading for the mains.

You need both voltage and current values to determine wattage...

Make sense?

:smiley_cat:

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Hello jkwilborn, I completely understand and makes sense about knowing the voltage and current to get amperage to get the wattage. Sense I don't have a ac adapter I know in code I will have to change to make this happen. But can I just bypass the adapter, Do I really need it?

4

You need real-time voltage to match to real-time current.

The power adapter is a safety feature. How else would you issolate the AC mains and create a low-voltage at the same time?

5

You can find these at thrift stores, by the dozen, very cheaply. Just make sure that the output is AC.

6

the out put is 9v ac adapter, It wouldn't change it is only to see if there is any voltage on line correct that is why it's on a analog pin, How does it change? for Isolation there is the CT clamp itself and can isolate it with some diodes to protect it if that is what is calling for to be isolated. Unless I'm wrong and I know I'm wrong most of the time. This time as well maybe.

7

That is true. But where I live the closes one is 20 miles away and I don't drive.

8

You are wrong...

AC voltages have a nominal span, each power corporation has working RMS limits, but even so there are brown-outs. Fact is, mucking with the RMS also directly affects Power calculations.

You must have galvanic isolation. Diodes are a dangerous joke and only create a death-threat.

Do it right, buy a $1 transformer.

Don't die: read:
Isolation Transformers Provide Galvanic Isolation | DigiKey

9

Okay. I'm wrong so what can I do without an adapter?

10

Order one from ebay. AC-AC Adapter 12VAC @ 100mA, 2.1MM Power Plug | eBay

11

Oh to be honest. I didn't think about buying one on ebay. Thank you.

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I found tons of them 9v ac adapters. I just order one for $4 dollars and a $1.99. Can't beat that. I'm sorry If I was wrong on this. I just couldn't figure out things like this. But I'm seeing I can't do this without the adapter either. Thank you again all for the help.

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For all readers of this thread, Please, please...
AC is a necessary evil in many projects, please use a "certified" (usually UL tested in U.S.) and read about issolation transformers:

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image969×951 151 KB

And, Stay Safe

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