DIY: Convert Your Mini Maglite to LED

Into the Woods with a White LED Mini Maglite

By Jack Arcade
Product Marketing Engineer

Description: Mini Maglite LED Conversion Kit
Assembly Time: 2 hours
Skill Level: Intermediate
Designer: Waltx

Flashlights are always useful especially if you like to camp like me. Out in the woods, when you are away from your iPhone flashlight, a Mini Maglite comes in real handy. Now, what if you hate its yellow color and carrying extra batteries? What if you want a white color for your flashlight and a longer battery life? Sound exciting? Let's make one.

Required Tools:
Mini Maglite

Mini Maglite Flashlight
Fine Tip Soldering Iron
Solder Paste or Liquid Flux
Tweezers
Pliers
PCB Holder
Voltmeter
Magnifying Glass
Tapered Reamer or #12 (4.8mm) Drill Bit and Drill Motor

Purchase the Mini Maglite LED Conversion Kit.

The kit includes:

Qty.
Part Description Manufacturer Part Number
1
3mm Nylon Spacer R30-6700394
1
10-Foot 24AWG Solid Bus Bar Wire 3819-10FT
1
0805 0.22µF SMT Capacitor GRM219R71E224KA01D
1
0805 1µF Multilayer Capacitor 0805ZC105KAT2A
1
Schottky Diode SOD-523F Package BAT54XV2
1
LED Driver IC, TSOT23-5 Package CAT4137TD-GT3
1
22µH Inductor, 1210 Package LQH32MN220J23L
1
White LED, T1.75 Package C535A-WJN-CU0V0231
1
12Ω Resistor, 0805 Package RC0805FR-0712RL
1
Printed Circuit Board
1
Instructions

Building the Kit

My experience building the kit will help guide you as you build the kit. Though this kit may look small and quick to finish, it requires SMT soldering skills and quite a bit of patience to build it.

If you have not done surface mount soldering before, don't jump into building this kit. Practice surface mount soldering first, then try this kit. It took me a bit longer to solder as I didn't use all the proper equipment for SMT soldering.

To get started, dismantle the head of the Mini Maglite and pull off the bulb by applying some force as it might be stiffly mounted.

Top View of Completed Triori
Your Mini Maglite should look like the image on the right.

Parts

Make sure you have all the parts of the kit with you as well as additional tools.

Mini Maglite LED Conversion Kit Parts
Mini Maglite LED Conversion Kit Parts (click to enlarge)

Once you have all the parts with you, figure out the capacitance of C1 and C2 using a multimeter. When distinguishing parts, keep in mind the resistor, inductor and IC are very distinct. Figuring out the terminals of the diode could be challenging though. You could either use the multimeter to determine the terminals of the diode or simply use a magnifying glass – just find the faint silver line on the diode, which should be the cathode, or the negative terminal.

Soldering

Use solder paste, solder flux and a soldering iron with a bevel tip to solder the parts perfectly. As the PCB is very small, you will need delicate hands and some patience while soldering.

Top View and Bottom View of LED
Top View and Bottom View of LED (click to enlarge)

Soldering the LED could be challenging as you need to keep some distance (0.1") between the LED base and the top surface of the PCB. Use a thin cardboard as mentioned in the instructions to do it. The PCB doesn't show the terminals of the LED but the instructions do. The cathode (shorter lead) of the LED is closer to the J1 on the PCB, thus install and solder in that fashion.

Assembly

After you solder the 24-gauge wires, make sure the total length of your assembled kit matches with that of the original Mini Maglite LED. The length needs to match the original length so as to properly close the focus control and lens cap. Make sure to use the spacer so the inductor doesn't get damaged while you adjust the focus.

Make sure everything is properly aligned and that you drill an optimum hole so that the LED doesn't slide against the body of the Mini Maglite (otherwise it gets caught to the surface and might twist the 24-gauge wire leads). Don't rush in assembling the Mini Maglite – take your sweet time doing it.

It's Ready!

Completed Conversion to LED
Completed Conversion to LED

It was fun building this kit – even though I had to do it twice. My first attempt with SMT soldering did not go well but after some practice it came together. This will surely be a useful flashlight – I think it will provide you with a constant current drive, giving you a constant light output independent of the battery voltage. And, you won't need to carry that extra set of batteries as your Mini Maglite's life expectancy just increased!

Hack your own flashlight.

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Jack Arcade earned his master's degree in Mechanical Engineering from Santa Clara University and works as a Product Marketing Engineer at Jameco Electronics. He specializes in the design and control of robots. Jack's interests include traveling, camping, trekking, river rafting, bungee jumping and mountain climbing.