There are many types of regulator IC and each type will have different pin-outs and will need to be connected up slightly differently. Therefore, this article will only look at one of the common ranges of regulator, the 78xx series.
There are seven regulators in the 78xx series, and each can pass up to 1A to any connected circuit. There are also regulators with similar type numbers that can pass a higher or lower current, as shown in the table below. In addition, variable regulators are available, as are regulators that can provide negative regulation voltages for circuits that require them.
| Type Number | Regulation Voltage | Maximum Current | Minimum Input Voltage | |||
| 78L05 | +5V | 0.1A | +7V | |||
| 78L12 | +12V | 0.1A | +14.5V | |||
| 78L15 | +15V | 0.1A | +17.5V | |||
| 78M05 | +5V | 0.5A | +7V | |||
| 78M12 | +12V | 0.5A | +14.5V | |||
| 78M15 | +15V | 0.5A | +17.5V | |||
| 7805 | +5V | 1A | +7V | |||
| 7806 | +6V | 1A | +8V | |||
| 7808 | +8V | 1A | +10.5V | |||
| 7812 | +12V | 1A | +14.5V | |||
| 7815 | +15V | 1A | +17.5V | |||
| 7824 | +24V | 1A | +26V | |||
| 78S05 | +5V | 2A | +8V | |||
| 78S09 | +9V | 2A | +12V | |||
| 78S12 | +12V | 2A | +15V | |||
| 78S15 | +15V | 2A | +18V | |||
Ripple voltage.
If using a regulator after the smoothing block of the power supply,then not need to worry about the ripple voltage, since the whole point of using a regulator is to get a stable, accurate, known voltage for your circuits. However, if the ripple voltage is too large and the input voltage to the regulator falls below the regulated voltage of the regulator, then of course the regulator will not be able to produce the correct regulated voltage. In fact, the input voltage to a regulator should usually be at least 2V above the regulated voltage. In our power supply circuit, the input to the 7805 regulator is around 12V, and the regulation voltage is 5V, so there is plenty of headroom. The maximum input voltage to any 78xx regulator is 30V.
Filtering is performed by a large value electrolytic capacitor connected across the DC supply to act as a reservoir, supplying current to the output when the varying DC voltage from the rectifier is falling. The capacitor charges quickly near the peak of the varying DC, and then discharges as it supplies current to the output. Filtering significantly increases the average DC voltage to almost the peak value (1.4 × RMS value).
Filtering is performed by a large value electrolytic capacitor connected across the DC supply to act as a reservoir, supplying current to the output when the varying DC voltage from the rectifier is falling. The capacitor charges quickly near the peak of the varying DC, and then discharges as it supplies current to the output. Filtering significantly increases the average DC voltage to almost the peak value (1.4 × RMS value).
To calculate the value of
capacitor(C),
C =
¼*√3*f*r*Rl
Where,
f = supply
frequency,
r = ripple factor,
Rl = load
resistance
78xx pin-out.
The 78xx, 78Mxx, and 78Sxx regulators all have the pin-out shown in the left of figure 1. The 78Lxx series, shown in the right of figure 1. The connection circuit of regulator 78xx, as shown in figure 2. For this project, it use 7805 because give regulated output is 5V and the micro controller only need 5V of source.
IC regulator LM7805
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