LED Christmas Star


Posted on Dec 23, 2012

This circuit can be used to construct an attractive Christmas Star. When we switch on this circuit, the brightness of lamp L1 gradually increases. When it reaches the maximum brightness level, the brightness starts decreasing gradually. And when it reaches the minimum brightness level, it again increases automatically. This cycle repeats. The increase and decrease of brightness of bulb L1 depends on the charging and discharging of capacitor C3. When the output of IC1 is high, capacitor C3 starts discharging and consequently the brightness of lamp L1 decreases. IC2 is an opto-isolator whereas IC1 is configured as an astable multivibrator. The frequency of IC1 can be changed by varying the value of resistor R2 or the value of capacitor C1.


LED Christmas Star
Click here to download the full size of the above Circuit.

Remember that when you vary the frequency of IC1, you should also vary the values of resistors R3 and R4 correspondingly for better performance. The minimum brightness level of lamp L1 can be changed by adjusting potentiometer VR1. If the brightness of the lamp L1 does not reach a reasonable brightness level, or if the lamp seems to remain in maximum brightness level (watch for a minute), increase the in-circuit resistance of potmeter VR1. If in-circuit resistance of potmeter VR1 is too high, the lamp may flicker in its minimum brightness region, or the lamp may remain in off state for a long time. In such cases, decrease the resistance of potmeter VR1 till the brightness of lamp L1 smoothly increases and decreases. When supply voltage varies, you have to adjust potmeter VR1 as stated above, for proper performance of the circuit. A triac such as BT136 can be used in place of the SCR in this circuit. Caution: While adjusting potmeter VR1, care should be taken to avoid electrical shock.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Bedwetting (Enuresis) Alarm with 555 timer
CW 250mW transmitter
Peak detect and hold
Amplifier-for-signal-supply
LED (IR LED1) and the phototransistor (T1) and wireless light switch
free energy generator from a candle
ua 741 square wave generator
Dark detector circuit
A potentially novel pre-amp for electret mic capsules which have their internal FETs Drain and Source connections available separately
flashingLEDs
Simple AM Transmitter
Quick and Easy Wireless Circuit
LED3X Solar Tracker Assembly
FM Transmission and Reception
Homemade whole integrated circuit amplifiers 01



Top