Voltage Regulator (LM7805) 11

The voltage regulator module is used to protect PIC and other connected sensors / actuators from over voltage. This is because PIC and all other connected sensors, actuators all support 5V DC only. Over voltage will cause any of the module burn.

LM7805

LM7805 is used to regulate voltage in the system and output 5V DC (max output current: 1000mA). It supports input voltage from 7V DC to 18V DC. If the input voltage is over, the LM7805 will burn or auto shutdown due to overheat.

The generated 5V from LM7805 will be noise filtered by 0.1uF ceramic capacitor and a 1000uF electrolytic capacitor. This is to avoid high frequency oscillation on the outputs which may cause system hang or unstable.

A diode is connected at the input of the LM7805. This is to avoid voltage connected reversely. An on/off switch is used to turn on/off the system and a LED (5V, 5mA) is used to indicate the system is power on/off. The LED is connected through 1KR resistor to limit current pass through LED is 5mA. 

Advantages
The 7805 series has several key advantage over many other voltage regulator circuits which have resules in it's popularity:

• 7805 series IC do not require any additional components to provide a constant, regulated source of power, making them easy to use, as well as economical, and also efficient uses of circuit board real estate. By contrast, most other voltage regulators require several additional components to set the output voltage level, or to assist in the regulation process. Some other designs (such as a switching power supply) can require not only a large number of components but also substantial engineering expertise to implement correctly as well.
• 78xx series IC have built-in protection against a circuit drawing too much power. They also have protection against overheating and short circuits, making them quite robust in most applications. in some cases, the current-limiting features of the 78xx devices can provide protection not only for the 78xx itself but also for other parts of teh circuit is is used in. precenting other components from being damaged as well.

Disadvantages

• The input voltage must always be higher than the output voltage by some minimum amount (typically 2 volts). This can make these devices unsuitable for powering some devices from certain types of power sources (for example, powering a circuit which requires 5 volts using 6-volt batteries will not work using a 7805).
• as they are based on a linear regulation design, the input current required is always the same as the output current. as the input voltage must always be higher than the output voltage. means that the total power(voltage multiplied by current) going into the 78xx will be more than the output power provided. The extra input power is dissipated as heat. this means both that for some application an adequate heat-sink must be provided, and also that a (often substantial) portion of the input power is wasted during the process, rendering them less efficient than some other types of power supplies. when the input voltage is significantly higher than the regulated output voltage (for example, powering a 7805 using 24 volt power source), this inefficiency can be significant issue.