Solar Charge Controller circuit

Thus it is evident that the solar charge controller is the most important part of the system. After some initial research, I was extremely interested in knowing the inner workings and circuits of the charge controller. 

However, after some further learning, I understood that making the complete solar charge controller would conflict with this project's aim of developing a low-cost lamp because buying individual components was proving to be much more expensive than the market alternative used (in the picture). It was also a complex circuit which I would not have the time to completely understand and execute adequately. 

However, I was still curious about the inner workings as an electronics enthusiast, so I decided to create a prototype of a simple charge controller, which fulfils the first and most basic function of the charge controller. (as discussed previously)

1 ) IC: The Integrated circuit used was the NE555. It is a readily available timer IC. I configured it according to the common monostable mode. The monostable mode aids in generating a single controlled pulse due to a trigger (vibrations).  The trigger voltage (received by pin 2) leads to a positive(high) pulse in pin 3 (output pulse generated here). The positive pulse triggers other components in the circuit to start charging the battery.   The trigger voltage is set low because it triggers other components which charge the battery. When the battery voltage reaches the upper limit of the threshold, the IC signals other components to stop and drains the excess power to the ground rail (done through the MOSFET. The trigger is recieved due to the 

2) SPDT relay: A SPDT relay is used to switch between 2 circuits. It has a Normally Open (NO)  Terminal and a Normally Closed (NC) terminal between which the input causes the COM terminal to change the current flow to either one terminal as output. When the battery needs to be charged, the IC activates the relay's NO terminal, which allows the circuit to charge the battery. If not, the relay remains in its default NC position. When the NC terminal is used it simply dumps the extra power received to the ground rail. 

3) Transistor: The transistor was used to amplify the signal received from the IC  and maintain an appropriate current flowing to the connected MOSFET. The collector is connected to the gate of the MOSFET and is responsible for switching on or off the gate of the MOSFET. The collector allows current to flow to the MOSFET when it receives a signal from the IC which is connected to the Base pin. 

4) MOSFET: A MOSFET is used to regulate the power and is also connected to the NO  of the relay. This ensures that the terminals are switched appropriately in the relay based on the status of the battery. The Gate of the MOSFET was connected to the collector of the transistor. When the MOSFET is on, it enables current to flow from the drain to the relay (through the use of a diode).  

5) Voltage Regulator: A Voltage Regulator was used to maintain a constant 5V in the circuit. It converts the input voltage of the power source (the battery) from 12V to 5V, which can safely be used by the IC and other components.  the LM7805 was used because it provides the needed 5V output voltage. 

6) Capacitors: 2 capacitors were used. One connected the output of the LM7805 to ground and the other connected the input to the ground of the LM7805. It is used to stabilise output voltage because any noise can affect the working of the sensitive IC. The input capacitor smoothes out fluctuations/spikes in the input voltage from the power source. 

6) Potentiometers: 2 Potentiometers were used. One's Vcc was connected to pin 2 of IC and another one's output to pin 5. Both also had ground connections. By connecting to pin 2, which is the trigger pin, it enables us to adjust the voltage at which the IC is triggered. By connecting to pin 5, which is the control voltage pin, enables us to set the control voltage of the IC. The control Voltage is used