Testing

Whenever possible, you should test each portion of your circuit to insure it functions properly before moving on to the next task. In this case,we can test this part of the circuit by verifying the input voltage, the output voltage, and the ground.

Start by connecting your multimeter probes to the ground. You can use another jumper wire from the ground circuit or you can use the heat sink of the voltage regulator. The positive probe should be attached to the output wire of the voltage regulator from the pin 3 circuit.

Then connect your 9 volt battery to the circuit. Insure the battery has sufficient power to supply your project. An old battery can cause a lot of frustration in wasted circuit troubleshooting.

Figure 7.18

Your multimeter should read almost exactly 5 volts. If it is registering a negative 5 volts, make sure your multimeter is attached to the circuit properly and the probes are connected to the multimeter properly. If it is registering a value other than 5 volts, insure you have 9 volts entering at the input circuit.

Figure 7.19