Notice: This post was first published in my old wordpress blogs at http://zidsdreamyworld.wordpress.com and http://ziddique.wordpress.com, these blogs now replaced with this website, so i am moving the post here to this site.
Here is one easy to build LED Torch Flashlight circuit powered using a rechargeable 3.7 V mobile phone battery. I am using this circuit for a long time, so i thought posting schematic of this torch flash light might be useful for some DIY people like me as it is a very useful circuit to build. this torch light circuit can provide good battery backup. the circuit uses 3 high bright white LEDs to provide sufficient light in the darkness. a recharge slot can be included in the circuit to recharge the battery using a mobile phone charger, so this cool circuit becomes cooler and useful.
How does this circuit work?
When you press the S1 switch, the 3.7V supply is passed to base of T1 transistor through R2 resistor, since the T1 is used here as a switch, it turns ON and since its lead is connected to the “-” (negative) or cathode terminals of the LEDs, all LEDs get forward biased and emit light. The charging section includes a Diode to protect the battery from discharging to the charger. L1 is used as an indicator for indicating that the torch is in charging mode.
D1 – 1N4007 diode
R1 – 1k resistor
LED1 – Red or any color LED
S1 – on/off switch
R2 – 560 ohms resistor
T1 – 2N5551 transistor(2n3904,s8050 etc can be used too.)
L2 – 3 low current bright white LEDs
3.7V cellphone battery
Suitable recharge slot
The circuit can be inserted in a tiny enclosure for comfortably carrying with you
- Do not turn the torch ON while charging as it may destroy the transistor or LEDs
- Unplug the charger after 1 hour of recharge, although new batteries are capable of protecting themselves, let’s just be on the safe side, just in case.
Circuit designed by Myself