The circuit is a small +5 volt regulator circuit, which is useful when experimenting with various electronic circuits. This circuit can give +5 volt output at about 150 mA current, but it can be increased to 1 Amp when good cooling (heatsink) is added to the 7805 regulator.
FEATURES:
· +5 Volt output
· Built-in overheating protection
· Built-in overload protection
· Very simple and easy to build
· Very stable output voltage
· Reliable operation
· Common basic components, readily available
· Minimal component costs
+5 VOLT VOLTAGE REGULATOR:
A Voltage Regulator (also called a “regulator”) has only three legs. A regulator converts varying input voltage and produces a constant “regulated” output voltage. Voltage regulators are available in a variety of outputs, typically 5 volts, 9 volts and 12volts ect. The last two digits in the name indicate the output voltage. ( 7805 = 78 Positive series; 05 Five-volt variant) The LM78** series of voltage regulators are designed for positive output. For applications requiring negative output the LM79** series is used.
Let's now have a closer look at the components of the 5 volt regulator. This regulator looks similar to a Transistor, but it is actually a complex Integrated Circuit.
The circuit diagram below represents a typical use of a voltage regulator.
COMPONENT LIST:
1. 7805 Regulator IC (IC 7806,7809 and 7812 can also be used. Note that the last two digits indicate the voltage output of the IC.)
2. 100 uF Electrolytic Capacitor 25 Volt
3. 10 uF Electrolytic Capacitor 25 Volt
4. 0.1 uF Ceramic Capacitor 25 - 50 Volt
5. Printed Circuit Board
6. Connecting Wire (Red + Black)
7. Heatsink (To be used when drawing full current from the 7805 IC.)
HOW IT WORKS:
The input voltage to the regulator in our circuit should be between 8 – 12 volt DC. A sound practice is to limit the input voltage to 2 to 3 volts above the output voltage. The LM78XX series can handle up to 30 volts input, but the power difference between the input voltage/current ratio and output voltage/current ratio appears as heat. If the input voltage is unnecessarily high the regulator will get very hot. Unless sufficient heat-sinking is provided the regulator will shut down. The 100uF capacitor on the input side helps to maintain a constant input into the regulator and helps with the smoothing of the input voltage. The 10 uF capacitor on the output side assist the 0.1uF capacitor to eliminate any high frequency pulses that could otherwise interfere with the operation of the regulator and helps with the smoothing of the output voltage.
Voltage regulators are very robust. They can withstand over-current draw due to short circuits and also over-heating. In both cases the regulator will shut down before damage occurs. The only way to destroy a regulator is to apply reverse voltage to its input. Reverse polarity destroys the regulator almost instantly. To avoid this possibility you should always use diode protection. This is especially important when using 12 volt battery supplies as it is common for people to 'test' the battery by connecting it one way and then the other. Even this short 'test' would destroy the regulator if a protection diode were not used. More on the protection diode later.
CONSTRUCTION:
Construction is simple and to the point. Refer to the component layout diagram to ensure that all the parts are placed correctly on the PCB. Care should be taken to install the polarized components as indicated. The 1N4001 protection diode does not feature on the circuit diagram and was later added for protection. If you wish to omit the diode, it can be replaced with a wire-link.
Component layout diagram:
PCB OUTLAY:
For the convenience of the homebrewer I have added the PCB Outlay for this project. However this project is so simple that it could easily be constructed on perfboard without any problems. Please note that the PCB is not to scale. FINALLY:
I know that this
project can be adapted and altered in many ways. However I want to
keep it simple (KISS) and as indicated before this project is
intended for the new and inexperienced Homebrewer. I trust that this
little circuit will be the start of bigger projects for you the new
Homebrewer. Built it and enjoy the benefit of constructing your own
projects.
