Sunday, April 21, 2013

UV Torch Light

UVrn (ultra-violet) LEDs can produce crowd pleasing effects when their gentle rnis permited to intrude with certain colours, particularly with rnreflected light underneath near-dark conditions. Also try shining some UV rnlight on a diamond.

Circuit diagram :
UV Torch Light-Circuit Diagram
 UV Torch Light Circuit Diagram

Mostrn UV LEDs require about three.6 V (the ‘blue’ diode voltage) to gentle. Here, arn MAX761 step-up swaping IC is used to provide constant current to biasrn the UV diode. The IC hires PWM in high-cur-rent mode and rnautomatically modifications to PFM mode in low or medium energy mode to shop tons of rn(battery) energy. To enable it for use with two AA cells, the MAX761 isrn configured in bootstrapped mode with voltage-adjustable feedback. Up torn 4 cells may be used to power the circuit however they are going to add more rnweight than you need to for a torchlight. 

Torn lengthen the switch life, R1 is connected to the IC’s SHDN (shutdown) rnpin. Less than 50 nA can be measured in shutdown mode. Electrolytic rncapacitor C1 is used to decouple the circuit supply voltage. With-out rnit, ripple and noise may just cause instability. The one inductor within the rncircuit, L1, can have any value between about 10 and 50 ┬ÁH. It stores rncurrent in its magnetic container whereas the MOSFET throughout the MAX761 is rnswitched. A toroid inductor is most popular on this position as it is going to rnguarantee low stray radiation. D1 must be a rather quick diode so rndon’t be tempted to make use of an 1N400x as a end result of it has a too gradual recovery rntime.
Thern circuit efficiency used to be measured at about 70%. R2, the resistor on the rnfeed-back pin of the MAX761 effectively decides the quantity of rnconstant present, I, despatched in the route of the UV LEDs, as follows: R2 = 1.5 / I
where I will doubtless be between 2 mA and 35 mA. 

Zenerrn diode D4 clamps the output voltage when the weight is disconnected, whichrn may just occur when one of the vital UV LEDs breaks down. Without a load, the rnMAX761 will change L1 right up to the raise voltage and so wreck rnitself.

Author : Myo Min