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.
Figure 1 - The flashlight
Figure 2 shows the original bulb still in the flashlight. As shown in Figure 3, this drawsabout 0.7 A from the batteries.
Figure 2- Original Bulb
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).
Figure 4 - The power LED
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.
Figure 6 - Series Resistor Calculation
Figure 7 - Install Resistor. First cut one trace.
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.
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...
Comments, questions, suggestions? You can reach me at: contact (at sign) paulorenato (dot) com