This experiment turns on a LED when a whistle is detected. The LED turns off when the whistle is detected for the second time.
This experiment detects the presence of light. A photo-darlington transistor is connected to the circuit via a plug and socket and exposed to light. The change in resistance of the photo-darlington transistor creates a voltage change across it and this is amplified by the circuit and delivered to an input of the microcontroller. The program turns on the 8 LEDs when the photo-darlington transistor detects change in illumination.
The photo-darlington transistor is connected to the circuit via a capacitor and only CHANGES in illumination are detected.
If the illumination is decreased, a point will be obtained where the circuit is sensitive to the changes in supply rail voltage. At this point the circuit will start to oscillate or MOTOR-BOAT.
The circuit must be re-designed to prevent this from occurring.
If the photo-darlington transistor is placed in a room with incandescent lighting, the 50 or 60Hz from the light will be detected. These pulses must be dealt with by the program to obtain a reliable HIGH/LOW pulse.
For more detail: Whistle-On Whistle-Off
Current Project / Post can also be found using:
- pic microcontrol tutorial pdf