Voltage Regulators

Next we will construct a 5 volt power supply for the microcontroller. Microcontrollers and other logic devices are sensitive to voltage spikes, so we will use a voltage regulator and several capacitors to insure a smooth, consistent voltage is applied to the microcontroller. The voltage regulator is a standard 7805, a 5 volt voltage regulator and the capacitors are two .01uf ceramic capacitors.

A reference diagram is depicted in figure 7.11 so you can get a top down view of the connections. When you are positioning the 7805 voltage regulator, notice the gray bar on the back of the IC's outline. The gray bar represents the metal heat sink on the back of the IC. With most common voltage regulators, the positive voltage input is on the left, the ground is in the middle and connected to the heat sink, and the output voltage is on the right. The directions are referenced to you looking at the front of the regulator.

Figure 7.11

Start by inserting the regulator in the middle of the first three bottom vertical rows with the chip facing the positive strip.

Figure 7.12

Next, insert the battery wires with the positive in the input pin circuit strip for the voltage regulator and the negative wire in the top negative horizontal circuit as shown in figure 7.13.

Figure 7.13

Insert the first .01uf ceramic capacitor in the center pin (ground) circuit and the first pin (input voltage, 9v) circuit as shown in figure7.14.

Figure 7.14

Insert a jumper wire from the horizontal ground strip to the center (ground) circuit of the voltage regulator.

Figure 7.15

On the front side of the chip, insert the second .01uf ceramic capacitor between the center pin (ground) circuit and the third pin (output voltage, 5v) circuit as shown in figure 7.16