measuring AC without ZMPT101B

Hello, i need to measure AC waveform with arduino… something like this
The problem is, i don’t have easy access to zmtp101b (i don’t have time to wait for delivery 2 months or so), zmtp obviously makes things alot easier and safer. So i wanted to ask if there is some easy and safe way around this? I have SRD-05VDC-SL-C module, but i don’t think this can be used for the same purpose.
Did anyone bump into some easy guide to this, or has any tips?
Thanks all

What voltages do You intend to measure?

Railroader:
What voltages do You intend to measure?

sorry, i forgot about this.. it's 230V

btw. found this on eshop, delivery time should be fine.. Is this suitable for this task? I should be getting the values i need from out pin

The translation, by Google I suppose, is really bad. It says that the module detects the presence of 240, nothing more.

Do You want to measure voltage or do You want to catch over tones, noise etc on the main? That's not clear to me.

Okay, sorry i realise that i've given you kinda shitty explanation. Well, my task is to measure voltage like U2 on picture i have shown here. The problem was that i know that messing with wall voltage and transformers can be pretty dangerous, so i was asking if anybody knows there is a safe and easy way to do this.
in my opinion the picture given isn't something you would plug into your arduino, since transformers can reduce voltage to safe level for arduino (if you pick the right one), but they don't handle negative values and arduino cannot handle these negative values as well. Is my idea about this right? Is there some way around this problem?

circuit.PNG

circuit.PNG

Well done posting that drawing! What is the range of V2/U2 You intend to use?
That's true, don't apply any negative voltage to the controller. (-0,5 something is the minit).

bergerino:
Hello, i need to measure AC waveform with arduino.. something like this
The problem is, i don't have easy access to zmtp101b (i don't have time to wait for delivery 2 months or so), zmtp obviously makes things alot easier and safer. So i wanted to ask if there is some easy and safe way around this? I have SRD-05VDC-SL-C module, but i don't think this can be used for the same purpose.
Did anyone bump into some easy guide to this, or has any tips?
Thanks all

The SRD-05VDC-SL-C is a relay. The other device is a current transformer with some additional circuitry.
Paul

Railroader:
Well done posting that drawing! What is the range of V2/U2 You intend to use?
That's true, don't apply any negative voltage to the controller. (-0,5 something is the minit).

If i understood your question right, the range would be basically anything that's safe for arduino, which is 5V - then you could calculate the values from 0-5V to 0-230V, i understand that this isn't the most accurate way to approach this, but it's a school project.
I found another approach though, what do you think about [this](Measure AC Voltage with Arduino - AC Voltmeter - Simple Projects Arduino reads the voltage,%3D 220mV (RMS values).")? minus the LCD display, i don't need that

That link doesn't work, "page not available".... And I don't spend time looking at videos and similar stuff.
Transforming to voltages like 5 to 12 volt is a good way to be safe.
Diodes can be used to only send the positive part of the AC curve to the controller. The disadvantage is that some voltage is lost across the diode. OP amp circuitry could compensate for that, only I have no diagram to send You.

It should be working now.
So, if i understood correctly, using even 12V as maximum voltage for analog input is still safe?
Yeah i thought a bit about diodes, though you are right that opamp is better way to do this. Anyways, thanks alot for your help

Paul: Oh okay, thanks. Do you think the second device would be useful?

12 volt level is safe for You but not for the controller. A 12 volt signal can be lowered to the 5 volt range using a voltage divider. Don't forget that 12 volt AC is the RMS value. The top value is 1.412 times 12 volt...

Railroader:
12 volt level is safe for You but not for the controller. A 12 volt signal can be lowered to the 5 volt range using a voltage divider. Don’t forget that 12 volt AC is the RMS value. The top value is 1.412 times 12 volt…

Alright, so transformer with 12V as secondary value would work fine, if i make voltage divider there? Is there any other parameter of transformer that i should watch out for?
Can i plug this into a computer? I would need to use serial monitor to watch this.

You might need to calibrate the transformer, compare low voltage out relative to mains in. As You will draw very little current from the low side some transformer variations will not disturb.
Do some research for precision AC measurements using Arduino. I don't have such stuff "on the shelf".

Railroader:
You might need to calibrate the transformer, compare low voltage out relative to mains in. As You will draw very little current from the low side some transformer variations will not disturb.
Do some research for precision AC measurements using Arduino. I don't have such stuff "on the shelf".

Alright, anyways, thanks again for help :slight_smile:

bergerino:
Paul: Oh okay, thanks. Do you think the second device would be useful?

Only as a relay!
Paul

Doorbell transformer will give you a sine wave.
Openenergymon.org shows how to measure the AC sine wave on a 5v GPIO pin

Search openenergymon.org arduino voltage for the schematic.

You probably have everything you need already.

The way I do it is use a transformer based wall wart that has a AC output. 4.5V is my favorite. I rectify it, add a cap and a load resistor (pot with the wiper to the arduino analog input. The cap and resistor have an effect on your response time.

gilshultz:
The way I do it is use a transformer based wall wart that has a AC output. 4.5V is my favorite. I rectify it, add a cap and a load resistor (pot with the wiper to the arduino analog input. The cap and resistor have an effect on your response time.

OP is asking for watching the waveform. What waveform does Your solution give? To me it looks like death... a straight line on the monitor....

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