The post explains a simple, compact, 220V, 120V transformerless light chaser circuit which can be used for illuminating mains operated lamps in a sequential chasing manner.
Main Technical Features
The chasing effect can be altered by means of pot controls. The system can be used as a decorative lighting during festive seasons like in Christmas and Diwali. The idea was requested by Mr. Ashish.
As usual, the proposed Diwali, Christmas light chaser circuit is built around the ubiquitous IC 4017 which is a divide by 10 Johnsons counter/divider IC.
It basically has 10 outputs in the order 3, 2, 4, 7, 1, 10, 5, 6, 9, 10 pinouts which can be made to shift in a sequential manner, one after the other by providing voltage pulses at its pin#14.
The above outputs can be either connected with LEDs for acquiring an LED illuminated chasing effect or can be terminated with triacs for driving mains operated lamps in the same fashion, as shown in the diagram below.
Referring to the circuit diagram, we can see that the IC1 is clocked or pulsed at its pin#14 through a transistorized AMV stage.
This transistor astable multivibrator produces alternate high and low pulses at the collectors which can be witnessed by the blinking red LED.
With every high pulse or blink of the LED, the output of IC1 sequences to the next subsequent output pin and continues to do this with every subsequent pulses at pin#14.
When the output reaches pin#11, the IC resets and the sequence returns to pin#3 for commencing a new cycle.
Here, since the outputs are terminated to gates of triacs, the triacs conduct with the same sequence illuminating the connected AC lamps producing a running or chasing effect.
The speed of this chasing or sequencing can be altered by simply adjusting the two pots VR1, VR2 appropriately.
The circuit runs from direct mains through a capacitive power supply and is therefore not isolated from lethal mains current, observe extreme caution while testing/handling the circuit while it's in an uncovered position.
CAUTION: NO MAINS ISOLATION PRESENT....HANDLE WITH EXTREME CAUTION TO AVOID SHOCKS, AND FATALITY.
R1, R2, R3, R4, R5----R15: 1K
VR1, VR2 = 100k
C1, C2 = 10uF/25V
C3 = 474/400V
C4 = 100uF/25V
D1 = 12V zener, 1 watt
D2 = 1N4007
R16 = 10 ohms, 2 watt
Triacs = BT136
IC1 = 4017
T1,T2 = BC547
LED = red, 5mm