Low Cost LED torch (it lasts 50 hours)

Its a very simple LED torch using very easily available components.
This torch costs you about 0.6$ and lasts for 50 hrs(approx).

components required are:
1).Hinged lockable plastic box.
2).Simple Switch
3).9 volt Battery
4).100 ohms resistor
5).8mm LEDs(we need a couple of them).........any type of LED can be used but carefully select the resistance value.
6).soldering equipment.

Step 1 One and only one step!

Make suitable dents in the box such that we can fit the switch and the two LEDs.

{longer arm of LED is + and shorter one is -}
connect longer arm of LED to + terminal of 9-V battery.
solder - of 1st and + of 2nd LEDs.(connecting them in series)
solder - of 2nd LED and 100 ohm Resistor.
R's other end to switch and Other end of switch to - of Battery.

THATS it our LED torch is finish....and ready to use.

Well performance of torch may be increased by using mirrors to direct the light.

Comments

[agis68]

It will be a miracle if lasts for 4-6 hours. Anyway i liked your bight, clear pictures. Good Camera though!!!!.....:)))

[alloqba]

It is impossible for this torch to last for 50 hours. Only the resistor, not counting LEDs will discharge it in below 6 hours.

Simple quotation:
Ohm=V/A -> A=V/Ohm
A=9V/100 Ohm
A=0,09 - power drainage =0,09A=90mA

Typical 9V battery capacity is 500mA, so 500mA/90mA=5,6, so battery will last only 5,6 hours before dead running only resistor for simplicity.

So, before you mislead people make equation, or simply experiment.

Btw, it would be MUCH more efficient to use proper voltage for leds without resistor, for example by using 2x 1,5V batteries.

[rcisneros]

I have to completely agree. Also since 9V's are the MOST expensive of the common batteries, I don't see how that is economical. A pair of cheap C batteries would give you 10,000 mAh @ 3v in parallel. If you wanted rechargeable it would be 3 C's 5,000 mAh @ 3.6v. That, more expensive.

[D5quar3]

 so your saying this will only last six hours before it breaks

[namdeo.d]

 i think this is very economical..
a new 9V battery just costs Rs.10