This circuit is not a voice operated
switch (VOX) because this circuit is too dumb to differentiate between
musical sound or human voice. This is rather a sound activated than
voice activated. One interesting application is to control your disco lighting automatically by the musical sound from high power amplifier, when the music signal is dominating the sound space. The schematic diagram is shown below.
You can use either moving coil
microphone or condenser microphone for this circuit. For condenser
microphone, you have to connect R1 resistor as shown by the dashed line.
Choose between 1k5 ad 22k to adjust the sensitivity, or use a 4k7 value
if you don’t care with the sensitivity fine tuning. Make sure the electrolytic capacitor is rated for 16 volt or more. The potentiometer shown in the schematic diagram is used to adjust the gain of the pre-amplification. You can adjust this potentiometer to get a proper sound level where the relay would be activated.
You can use this circuit to give auto trigger for your secondary flash light. You don’t have to worry about wiring
for the control, because using this circuit your secondary flash will
be automati8cally triggered when it receive the light signal from the
primary flash. Look at the circuit’s schematic diagram below.
The inductor 68mH is connected in parallel
with the solar cell to prevent the false trigger by slowly changing
environment light. Bright daylight won’t trigger your slave flash lamp
because the output will be shorted by the inductor. Only fast luminance change caused by your primary flash lighting will trigger your secondary flash light.
The solar cell should be 100mm2 at minimum (about 1cm2), and you can
easily find on many electronics part store, and sure you can use a
larger one for better sensitivity. For the inductor, because it is
relatively huge, you can use a radio frequency choke (RFC) that usually
used in AM radio transmitter circuit, but any inductor with low enough resistance could be used.
Using a standard fluorescent tube lamp (TL), you can make your own disco light, similar to a stroboscope light. You can even use a half-broken lamp, which one side of the heating filaments has broken. This circuit use only one side heating filament inside the tube. Look at the circuit’s schematic below.
Please be aware that this circuit
uses high voltage from your main power line, can be very dangerous.
Although the control circuit uses 12 volt supply, it isn’t isolated from
the SCR driving the high voltage. The only isolation is the audio transformer connected to your audio amplifier.
R1: 470k; R2:100k; R3:3k9; R4:18k;
R5:10k; R6:2k7; R7:33k; R8:1k; R10:2k2; R11:2k2; P1:10k; P2:10k;
C1:0.1uF; C2:10uF/16V; C3:47uF/16V; TUN: 2N3904 or BC547.
This is a Light position controller circuit. Light position controller is a monolithic integrated circuit which is used in passenger cars. Potentiometer on the dashboard is used to define the light beam’s elevation of the head light of the car to a state by the car driver. Here is the circuit:
This circuit has some features, they are Thermally protected, Low supply current, Low positional error and Low noise
sensitivity due to hysteresis. besides that this circuit has Brake
function by short-circuiting the motor, Broken wire and short-circuit
indication on SET input and the Hysteresis level set externally.
[Source: NXP Application Note]
This is a circuit of light ignition
circuit. This circuit uses the LIC01 which is designed for high voltage
pulse generation circuits. This circuit can be used in many application such as lamp flashing, metal halid lamp and high pressure sodium lamp. When this circuit is used in high surge current operation in rugged environmental conditions, the high performance planar diffused technology device is used. Here is the circuit :
The LIC01 will decrease from an
off-state to low voltage on-state condition, when the voltage through
the device reaches the breakover voltage. The device will come back to
off state when the current across the circuit decreases below holding current Ih.
The LIC01 will turn on and produces a pulse of current across the
the transformer’s primary, when the peak voltage across C1 reaches the
LIC01′s VBO (break over voltage). In turn, the lamp will receives high
voltage pulses which is generated by transformer. [Source: STMicroelectronics Application Note]