I am new in the forum so forgive me for any trivial omissions.
I need to design a monitoring system for 15 small PV modules (max up 15V and 6A each) based on Arduino UNO, in which a measurement is performed once every hour to obtain short-circuit current and DC open-circuit voltage.
I found out I could use current sensors (like ACS712) and voltage sensors (just a voltage divider) to measure these data, and multiplexer (like 74HC4067 with 16 channels) to have multiple inputs. Each channel would be connected to one single PV module and ideally I would use one multiplexer board for voltages and one for currents.
My question is, before I even start design any sketch, is it possible to place only one sensor between each multiplexer and Arduino, or do I need to place one sensor for each channel (between multiplexer and PV module)?
Thanks for the help, I can further clarify if needed.
Can you post an annotated schematic showing how you propose to do this. From what you have said you will be passing current through a 4067 which will not survive.
please make a drawing/schematic of your "system" you want to monitor. PV Modules, solar controller, batteries, power consumers - real everything.
Furthermore also draw what power you use for your measurement device.
Welcome! For your project, you’ll need a separate sensor for each PV module. Each module will have different voltage and current values, so you need individual voltage dividers and ACS712 sensors for accurate measurements. You can use a multiplexer like the 74HC4067 to manage multiple inputs, connecting the outputs of the sensors to the multiplexer and then to the Arduino. This setup allows you to switch between channels and read the data sequentially. Good luck with your project!
Do you think it is a better solution than using separate voltage divider and current sensor? Why so?
In this case the MOSFET must be placed as a 'bridge' between the input pins of the sensor, right?
The purpose is not so relevant for the set-up of the monitoring system, however the data is used to quantify the degradation of the panels in different specific conditions, that is why the measurement is regular
I understand, but since Voc is mainly related to temperature changes, either you have to monitor panel temperature precisely, or you could skip Voc measurements and relay/mosfet switches.
The cells are all encapsulated with different compatible liquids and exposed to sunlight for 2 months, so we want to measure different degradation resulting from the operation. In this context measuring Voc, Isc and T is needed to have a complete picture and draw conclusions
An ACS712, 5Amp version, has a sensitivity of 185mV/A.
0.185 / 5 * 1024 = 38 A/D values per Amp if you use an Arduino with 10-bit A/D.
An INA-xxx could give you a higher resolution. Both current and voltage.
Leo..
Would it be possible to connect all panels to only one current sensor and one mosfet for the open circuit measurement? But then put another mosfet in each line and activate only one of them at a time.
So keep all panels disconnected except one at a time to do the measurements.
If it would work, you would need only one sensor, 15 + 1 mosfets, and a multiplexer.
Between measurements rounds all panels could be connected to avoid problems with the power.
Will you have a load for each PV?
If so, then you will need a digital channel to control the unload of the PV to get open circuit voltage.
Will you be measuring short circuit current?
If so then you will need a digital channel to switch the short to the PV?
What parameters will you be logging from the PVs?
Please list all your parameters and timing you want from your PV test bench.
Hey Tom, thanks for the reply.
The PV modules are not loaded. As I wrote, I need to measure open circuit voltage and short circuit current, so these are the only two states the panels will operate. Plus temperature of the back glass of each panel.
These parameters are taken every hour
