Problem with reading the voltage divider sensor

Other Hardware Sensors
1

Hi everyone, I'm a new member here.
I want to find a solution related to voltage sensor readings in my thesis project.

My thesis is about Maximum power point tracking (MPPT) using a single-ended primary-inductor converter (SEPIC), hence need voltage and current sensor to run the algorithm. I use two voltage and current sensors each for the input and output of the converter.

when I want to calibrate the voltage divider sensor on the input side of the converter, I find that the ADC value starts to fluctuate and is unstable when I give the converter a duty cycle of around 40% or above. but strangely this ADC fluctuation does not occur on the output side regardless of the duty cycle value that I give.

I've tried measuring the voltage divider sensor on the input only to see the voltage divided by the multimeter, and I've found that the voltage fluctuates when I activate the converter.

Please help me find a solution to fix it, thanks.

note:
resistor values 10k and 1k (2x I/O)
current sensors ACS712 30A (2x I/O)
input voltage 18V

Ignore Vout and ADC2
what i got

WrongReading
WrongReading1454×878 297 KB

2

Hello
Do you have to use the am current sensor ?
If yes, than take some time and study the tutorials avaibable and check the given restrictions.
If not, than take some time and read the datasheets if the INA2xx familie sensors.

Have a nice day and enjoy coding in C++.

3

Off hand I would suspect the input to your converter has more noise than the output. I would suggest you add a 0.1µF capacitor at the instrumentation side of the divider.

5

I think yes, because I use it on a 100 wp solar panel with specifications like this.

photo1632460808
photo1632460808960×1280 134 KB

do you have a better sensor recommendation to use on my system?

6

Hello
Well, my recommadation is to made a selection matrix with design goals vs sensors to find the best sensor for your project.

7

If you are writing a thesis you should already know that the first time you use an acronym you should show it in full; eg

MPPT or Maximum Power Point Tracking is ...

The single-ended primary-inductor converter (SEPIC)

You have not said what FREQUENCY the SEPIC is using; that will affect the values you need to filter out noise introduced by the SEPIC which is changing the load on the solar panel - and hence its voltage; and also the voltage produced at the output.

  • Like the buck–boost converter, the SEPIC has a pulsating output current. The similar Ćuk converter does not have this disadvantage, but it can only have negative output polarity, unless the isolated Ćuk converter is used.
  • Since the SEPIC converter transfers all its energy via the series capacitor, a capacitor with high capacitance and current handling capability is required.
  • The fourth-order nature of the converter also makes the SEPIC converter difficult to control, making it only suitable for very slow varying applications.
8

yeah, sorry about that sir.

9

I use 62.5 kHz switching frequency, with a target output voltage of 24 volts
the electronic components that I use for the filter circuit are, capacitors 470uF/50V (2x), toroid inductors 28,6uH (2x), MUR3060 diode, and IRFP450N mosfet.

10

Is it like this
test

11

Thanks for the advice.

12

Update post, hello everyone I have found the problem causing the voltage sensor reading on my converter. The cause of the problem is the poor grounding quality of the converter so it requires a direct ground from the arduino.
Thanks to everyone who read this post and provided suggestions. :grin:

13

Yes, Unless you need fast response a filter into the analog pin is always desirable.

14

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