I'm working on a voltage step down converter to couple a solar PV to a Battery doing the control part with an MPPT algorithm with Arduino.
The problem that i'm facing is that the control software obviuosly requires the measurement of the voltage of the PV on one side and the Voltage of the Battery on the other side but the scheme that i'm using to measure voltage is not working.
Below you can see the board that i built to make this buck converter and how i'm measuring the Voltage. The step down circuit is doing its job properly (if i measure the voltage with an external tester instead of using the Voltage sensor i see a correct reduction), but when i try to measure the voltage using the connection below i have a short current problem.
I made some experiment to understand the root cause and i think it depends on the connection to the GND that the Voltage sensor requires that cause a shortage with the GND connection of the MOSFET.
Any suggestion on how to make this sensor read properly the Voltage will be very appreciate.
Your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with (nor for advise on) your project See About the Installation & Troubleshooting category.
Please post a circuit diagram. A picture of a custom circuit board is almost useless.
Post our code (read the how/what to post guide first).
What sort of PV current are we talking about.
The blocking diode suggests several amp, but the size of the inductor suggests a few milliamps.
Leo..
Uhm, why? There are perfectly good step up DC DC converter ICs that handle all the work you're trying to do with an Arduino. This includes the various safet provisions you'll need to protect battery, mosfet and load. Is there a particular reason you're reinventing the wheel?
Yes i got your point but the reasons i'm doing that is because on one side i want to gain confidence with Arduino for a wider project that i'm trying to develop and this could be a good exercise. Second reason is that i also need to implement the MPPT algorithm and to do that you would need anyway to use Arduino to control the PWM signal. As far as i know in the simplest ready-to-use step down circuits the voltage is adjusted mechanically by a screw.
Wouldn't that imply that your regulator won't follow the load; i.e. it may/will not maintain 12V depending on load? How will you manage that part?
What's the output voltage going to?
Also, I second what @Wawa says. You mention a current of >1A and your inductor will handle maybe 10mA, so if you get this to work, it'll only work for a few milliseconds.
I still don't see the advantage of trying to solve this in an Arduino in the presence of off-the-shelf components to do this. A quick search turns up for instance ST's SPV1040 which seems to be a near perfect fit for your application. Surely alternatives exist as well.
I'm not talking about a ready-made module. Although evidently ready-made MPPT-enabled battery chargers are also available off the shelf.
I wasn't aware of these integrated modules so thank you i will consider them for the next developments.
But i would like still to understand what is not working with my actual circuit. As i said the step down part of the circuit is working well, the problem rises when i try to measure the voltage.
For this reason i simplify a lot the circuit, excluding the buck converter, to try to isolate the problem:
So now the PWM acts on a simple LED trhough a MOSFET and there is a voltage divider to monitor the voltage on A1 pin.
Again with this kind of connection with both the Mosfet and the divider connected to the GND the circuit doesn't work, while if i disconnect the GND of the voltage divider, circuit works but of course the voltage is not measure.
It's clearly a layout problem but i can't find a solution. DO you have any suggestion?
Thanks
EDIT: in the figure the resistor values of the voltage divider are switched
See 
