An entertaining small electronic project that produces sound according to the quantity of light it senses, is the light dependent screamer circuit.
A light dependent resistor LDR or resistor that adjusts its resistance in response to light intensity is used in this circuit.
All in all, the circuit functions as a little ‘screamer’ that increases in volume or pitch as the light grows brighter.
Circuit Working:
Parts List:
| Component Type | Value | Quantity |
|---|---|---|
| Resistor | 1k | 1 |
| Light Dependent Resistor (LDR) | 1 | |
| Capacitors | Electrolytic 10μF 25V | 1 |
| Ceramic 100nF | 1 | |
| Semiconductors | IC 555 | 1 |
| Other Components | Speaker 8Ω | 1 |
This is how the circuit works:
It generates a pulsing signal whose frequency depends on the quantity of light striking a light dependent resistor LDR using an integrated circuit, a 555 IC.
The Light Dependent Resistor LDR loses resistance in response to light.
On the other hand resistance rises with decreasing light.
A flexible integrated circuit that may be used to many timing tasks is the 555 IC.
It is set up as an astable multivibrator in this circuit.
This indicates that it can produce a square wave output signal without the aid of an outside trigger.
R1 and C1 together with the LDR regulate the astable multivibrators timing.
While the resistance of the LDR varies according to the quantity of light it receives R1 is a fixed resistor.
The frequency of the output square wave is determined by the LDR and R1 which are used to charge and discharge the capacitor C1.
Bright light causes the LDRs resistance to be low, which causes C1 to charge and discharge rapidly producing a high frequency output.
On the other hand C1 will charge and discharge slowly, producing a low frequency output when the LDRs resistance is high i.e low light.
The power supply voltage is smoothed down by the decoupling capacitor C2.
Speaker protection is provided by C1, which restricts the maximum current that may pass through the speaker.
At the frequency determined by C1, R1 and the LDR the speaker generates an audible square wave.
Therefore, the pitch of the music emerging from the speaker will alter in jointly with variations in light levels.
Formulas:
Design an astable multivibrator circuit using an IC 555 timer to create a light dependent screaming circuit.
Here is how to make the formula works in this circuit.
Formula for Frequency (f):
The following formula provides the frequency (f) of oscillation in an astable multivibrator circuit that uses an IC 555:
f = 1.44 / (R1+2×R2)×C
where,
- R is the resistor connected to the IC 555.
- C is the capacitor connected to the IC 555.
The Light Dependent Screamer Circuit makes use of an LDR and an IC 555 in astable mode to generate audible tone or sound variations in response to changes in surrounding light.
The circuits sensitivity and responsiveness to light may be customized by adjusting R, C1 and C2.
This makes the circuit appropriate for applications like interactive sound effects or light sensitive alarms.
How to Build:
To build a Simple Light Dependent Screamer Circuit follow the below mentioned steps for assembling:
- Gather all the components as mentioned in diagram.
- Connect pin 1 of IC 555 to ground.
- Connect pin 2 of IC 555 to pin 6.
- Connect pin 3 of IC 555 to ground through capacitor C1 and 8 ohm speaker.
- Connect pin 4 of IC 555 to positive of 6V.
- Connect pin 6 of IC 555 to pin 3 through series of resistor R1 and LDR.
- Connect capacitor C2 to ground from pin 2 of IC 555.
- Connect pin 8 of IC 555 to positive supply of 6V.
Note:
- It is crucial to keep in mind that this circuit is really basic and that the sound it generates may not be the most enjoyable scream.
- However, it provides a solid overview of the process of building interactive circuits using electronics.
Conclusion:
In conclusion, a simple electronic project that converts changes in light into auditory beeps or screeches is a light dependent screamer circuit.
Through the use of a IC 555 and a LDR, the circuit produces a pulsing signal whose pitch and frequency vary in response to the quantity of light it receives.