Audio Controlled Incandescent Lamp Light Controller

This is a design circuit for an audio-controlled lamp circuit. This circuit requires low voltage input such as pre-amplifiers, tone control, or general audio line level output. It’s also possible to feed the input with signal from small power amplifier output, or high power amplifier witk low volume level. The characteristic of lamp dimming (incandescent lamp) will look like coming from proportional controller since the switching rate of the TRIAC would be much higher than the lamp dimming response. This is the figure of the circuit;

 

If the lamp won’t go off after the audio signal back down to zero, then try to adjust the potentiometer. You can use filament transformer (usually used for tube), or you can also use small tv-antenna-booster transformer (20v-220V), or other small transformer below 500mA. Don’t worry if you can’t fine transformer with exact primary-secondary ratio, since the potentiometer is there for fine adjustment, and you can always change the input voltage level of the audio input signal.

Car Interior Light Extender Circuit

This is a circuit for a Courtesy Light Extender for cars. When a door is closed in a car, it extends the ON time, so the passenger can see where he/she is sitting. This is the figure of the circuit;

The light normally goes off immediately when door switch is opened, but the circuit takes over and allows current to flow because the 22u is not charged and the first BC 547 transistor is not turned ON. To illuminate the interior light, this turns on the second BC547 via the 100k and the BD679 is also turned. The 22u gradually charges via the 1M and the first BC547 turns on, robbing the second BC547 of “turn-on” voltage and it starts to turn off the BD679. When the door is opened, the 1N4148 discharges the 22u.

20VAC 60 Watt Sunrise Lamp Circuit

This is a circuit for a 120VAC lamp is slowly illuminated over a approximate 20 minute period. The bridge rectifier supplies 120 DC to the MOSFET and 60 watt lamp. A 6.2K, 5 watt resistor and zener diode is used to drop the voltage to 12 volts DC for the circuit power. The bridge rectifier should be rated at 200 volts and 5 amps or more. This is the figure of the circuit;

In operation, a 700 Hz triangle waveform is generated at pin 1 of the LM324 and a slow rising voltage is obtained at pin 8. These two signals are compared at pins 12 and 13 to produce a varying duty cycle rectangular waveform at pin 14, which controls the MOSFET and brightness of the 60 watt lamp. When power is applied, the lamp will start to illuminate within a minute or so, and will slowly brighten to full intensity in about 20 minutes. You can make that longer or shorter with adjustments to the 270K resistor at pin 9. The 2.2 ohm resistor and .015uF cap connected to the lamp serve to supress RFI. The diode at pin 9 and 10K resistor on pin 8 are used to discharge the 3300uF cap when power is removed. Power should be off for a few minutes before re-starting. This circuit is connected directly to the AC line and presents a hazard if any part is touched while connected to the line. Use caution and do not touch any parts while the circuit is connected to the AC line. You may want to use a 9 volt battery connected across the 12 volt zener to check the basic operation. The DC voltage at pins 1,2,3,5,6,7 will all be around 4.3 volts if the circuit is working correctly. If the DC voltages are all correct, you can use a variac to slowly apply the full line voltage and check for proper operation.