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[General] isolated dc voltage measurement

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archusvijay1

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i want measure a battery voltage (24V), using arduino,the controller side and battery side wants to isolated also.so i done it with the help of an optocoupler PC817, during the battery charging mode the battery voltage can be measured perfect but during inverter mode( sourcing from Battery) the reading is some more higher value than i measured. how can i solve this problem?
 

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Hello!

First thing to solve your problem:
1. Say hello, say thank you at the end, say please if you ask something. That may help you to get
a reply.
2. Explain your problem in correct english. Not asking native level, I'm not native either. But if you
begin a sentence with a capital, finish with a period and insert a few newlines, I'm sure your explanation
will be clearer even to yourself. There is one old saying: a well explained problem is half resolved.

I have the impression you wrote everything without breathing.

You may consider attaching a drawing of what you did.

Dora.
 
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archusvijay1

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Hello!

First thing to solve your problem:
1. Say hello, say thank you at the end, say please if you ask something. That may help you to get
a reply.
2. Explain your problem in correct english. Not asking native level, I'm not native either. But if you
begin a sentence with a capital, finish with a period and insert a few newlines, I'm sure your explanation
will be clearer even to yourself. There is one old saying: a well explained problem is half resolved.

I have the impression you wrote everything without breathing.

You may consider attaching a drawing of what you did.

Dora.

Sorry for my bad english.

Please find the attached schematic & how can i solve this issue.
 

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  • SCHEMATIC1 _ PAGE1.pdf
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doraemon

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Hello!

I'm not an expert in optocouplers, but it's probably not linear.
Depending on the input current, your output voltage will vary, and you have to input pin 2 of J2
to an analog measurement input of your µC.
Now what do you want to know?
Tell us what you already did and where the problem is, and it will be easier to reply.

Dora.
 

archusvijay1

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Hello,
Input 2 is connected to the analog input of the microcontroller. i want to measure the battery voltage of an offline inverter.

During the battery charging mode the battery voltage can be correctly measured.butduring the inverter startup (when input failure) the measured reading is some more higher than the actual voltage.Why this hapend and how can i rectify this problem?
 

doraemon

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Hello!

First you might consider using an oscilloscope to verify the exact voltage you want to
measure. When you know what to search, it's easier.
Once you know the real value, you can adapt your hard / soft to what you are measuring.
Without the schematic, it's not easy to reply.

Dora.
 

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