Converting a flashlight to LED.



Converting a Flashlight to LED

Most new flashlights in the market these says are LED based. This is for a good reason. For the same light output, LEDs are far superior in terms of battery life over their incandescent bulb counterparts. There are however a huge number of old flashlights out there using incandescent bulbs. I recently bough a good quality "Brinkmann" model from a garage sale for only $1 (see Figure 1).  This is a very good quality flashlight with all metal construction so I thought it would be worth the effort to convert it to LED. Furthermore, I already owned some high-power white LEDs I had no specific use for, so I decided to convert it. The followign images show the steps I took. hese are pretty much self-explanatory so I'll keep this article short.

IMG 3705

 Figure 1 - The flashlight

Conversion Steps

Figure 2 shows the original bulb still in the flashlight. As shown in Figure 3, this drawsabout 0.7  A from the batteries.

IMG 3712 

Figure 2- Original Bulb


 IMG 3717

Figure 3 - Measuring the Current Consumption

Figure 4 depicts the power LED I used in the conversion while Figure 4 shows it draws about half the current (with even more light output as we will see further down).

IMG 3725

Figure 4 - The power LED


IMG 3727 

 Figure 5 - LED current

With the LED, you will need to add a series limiting resistor. the calculation is shown in Figure 6. I'm assuming the internal battery source resistance(Rs)  is about 1 Ohm. R1 is the actual series resistor added to the circuit. At the end, I ended-up using a 1.2Ohm resistor since this was the nearast value available to me. Figures 7 and 8 show how I installed it in the LED power module.


 IMG 3729

Figure 6 - Series Resistor Calculation


 IMG 3730

Figure 7 - Install Resistor. First cut one trace.


 IMG 3734

Figure 8 - Install Resistor in series

The following figures show the final steps where I soldered the LED module to the battery contacts inside the flashlight.  


IMG 3741

Figure 9


IMG 3745

Figure 10


IMG 3748

Figure 11



Finally here are the results. These photos were taken with the same camera exposure setting (aperture and shutter speed) so the comparison is fair. The photo on the left was taken before the conversion whereas the one on the right was taken after the LED conversion. The photos speak for themselves...


Figure 12

IMG 3749

Figure 13

 Comments, questions, suggestions? You can reach me at: contact (at sign) paulorenato (dot) com