Need to understand the functioning of this circuit.It is Charge controller..

Where did you take that image from? There should be a description on the website.

Some basic functions I identified:
1) 7805 generates a 5V supply voltage for the circuit from 12V battery voltage.
2) ADC8031 measures the voltage of the battery.
3) IC3 and T3 form an isolated driver tu turn on or off the load.
ZD1 and T1 is an overvoltage detector for the voltage from the solar panel. If the voltage on the panel is greater than approx. 16V (note the divider R8/R9) pin P3.4 of the µC receives a low signal. Otherwise high level.
4) IC1 does alll the controlling. You need the description or (better) the source code for the software running on IC1 to understand what the circuit does.
5) Switches, pushbuttons, LCD - obvious.

Harald

 

Sorry, but I will not analyze 33k of assembler code listing. Specially as it is only sparsely commented and no description of the overall working is given.

Have you tried to contact the publisher of the circuit/code?

 

You could have asked that in the first place.

BS170 is an n-channel MOSFET. It is driven by the µC's pin 3.5 at the gate. If the gate is low, the transistor is open, the relay is de-energized and the NC contact (normally closed) is connected (as shown in the diagram).
If the gate is high, the relay is energized and the NC contact is open (inverse position to the diagram).

 

Which zener diode do you refer to? D1...D4 are standard diodes and you can't possibly mean ZD1, do you?

The relay coil is connected to the battery's + pole and to the transistor. If the transistor is on (gate = high) the the other pin of the relay coil is connected to ground. Thus a closed circuit from battery "+" <>coil <> transistor <> battery "-" is created and the relay is operated.

 

The diode within the MOSFET is the body diode which is automatically generated due to the structure of the MOSFET. It is of no importance here.

Harald