Variety of light-controlled electronic birds

Variety of light-controlled electronic birds

The light-controlled electronic bird introduced in this article is an interesting electronic toy. It uses the changes in the intensity of the light shining on it to emit bird calls with varying pitches. Especially under the illumination of unpredictable neon lights, its sounds are infinitely varied, and it is commonly known as the "variable light-controlled electronic bird". It is suitable for electronic enthusiasts to explore and learn.

1. Circuit Principle Electronic Bird

As shown in the circuit diagram 1. The NE555 time base circuit, resistor R1, photoresistor RG and capacitor C1 form a typical astable oscillator circuit (also called a multivibrator 1). After the power is turned on, the circuit starts to oscillate, and the third foot of the 555 will alternately appear high and low levels, driving the speaker to sound, and its tone will change with the change of the oscillation frequency.

The oscillation frequency of the circuit is t=1.44/[(R1+2RG)・C1], where RG in the denominator is the resistance of a photoresistor. A photoresistor is a passive photosensitive device that uses the photoconductive properties of semiconductors such as cadmium sulfide and cadmium selenide (CdS, CdSe). Its resistance changes with the intensity of light; when the light is strong, the resistance is small; when the light is weak or there is no light, the resistance is large. When the light intensity changes, the oscillation frequency of the circuit changes.

When using, place the photoresistor RG under the light, and then shake your fingers up and down and left and right over RG to change the intensity of light projected onto RG. As long as the fingers are controlled well, the speaker can simulate a variety of bird calls that are high and low, ever-changing, and very realistic.

2. Component Selection

The integrated circuit IC uses the NE555 time base circuit; RG uses the MG45 type non-sealed photoresistor, whose response wavelength peak is 0.56-0.58 microns; R1 uses the W metal film resistor; C1 uses the ceramic capacitor; C2 is the electrolytic circuit; B uses the 8-ohm small speaker; the power supply can be 4 No. 5 batteries or a 6V adjustable DC regulated power supply. The wiring diagram is shown in Figure 2.

3. Installation and debugging

1. After welding according to the circuit diagram, check if there is no error or omission, and the circuit can work normally without debugging. If there is no sound, you can use a multimeter to check the output voltage of pin 3, and the normal value is about 4V.

2. The printed circuit board, speaker and battery can be placed in a box of appropriate size, and then a bird model (commercially available velvet bird) can be placed on it. When you gently touch the bird with your hand (that is, shake it on the photoresistor), it will listen to your command and sing a song. It's really interesting!

3. A common small power switch (K) can be installed as needed.

4. The greater the difference between the dynamic resistance values ​​of the photoresistor device between light and dark, the more obvious the effect of the bird's song will be.

4. Improvement

To increase the power of the sound, it can be improved according to the schematic diagram 3. After the variable frequency signal of 555 is limited by R2 (240 ohms), it drives the small power tube VTI (9013) and emits variable bird calls through the speaker, which can be heard even 50 meters away; especially under the illumination of neon lights with changing light, the bird call effect will be better. Its wiring diagram can be slightly modified on Figure 2, disconnect at X and Y, and then weld R2, 9013 and the speaker according to the schematic diagram 3. The wiring diagram is shown in Figure 4.