800W-soft-start-light-dimmer


Posted on Jun 9, 2012

The zener provides a constant voltage of 20 V to unijunction transistor Ql, except at the end of each half-cycle of the input when the line voltage drops to zero. Initially, the voltage across capacitor Cl is zero and capacitor C2 cannot charge to trigger Ql. Cl will begin to charge, but because the voltage is low, C2 will be charged to a voltage adequate to trigger Cl only near the end of the half cycle. Although the lamp resistance is low at this time, the voltage applied to the lamp is low and the inrush current is small.


800W-soft-start-light-dimmer
Click here to download the full size of the above Circuit.

Then the voltage on Cl rises, allowing C2 to trigger Ql earlier in the cycle. At the same time, the lamp is being heated hy the slowly increasing applied voltage. By the time the peak voltage applied to the lamp has reached its maximum value, the bulb has been heated sufficiently to keep the peak inrush current at a reasonable value. Resistor R4 controls the charging rate of C2 and provides the means to dim the lamp. Diode D6 and resistor R7 improve operation at low-conduction angles.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Multipattern Running LEDs
LCD to a PC Parallel Port
LED Dice circuit
Remote controlled LED
Three-phase switch
Simplified-voltage-level-sensor
74LS192 Computer controller 4 DC motors
NE 555 & LM 567 Remote Control Circuit
Low Frequency Sine wave Generators Schematic
Noise Floor Measurement Circuit of PLL Frequency Synthesizers
220 volt disco lamp circuit
USB Ultra IR-Receiver v2.0 to PC remote control and power ON - OFF
Touch Switch And Delay Circuit
Milliammeter table circuit composed of resistance



Top