A Jam Flashlight

How I created a simple LED flashlight with basic electronics parts.

I wanted to buy a flashlight to have around the house in case of an emergency. And then I thought, "why not make one of my own?".

I have a degree in Electronics, although I never practised it professionally. It was a good opportunity to freshen up the basic knowledge I had, and another fun project to begin.


So I started with schematics. The design is simple:

  • 1 Power source (4 AA batteries in a row).
  • 4 white LED (Light Emitting Diodes) in parallel connection.
  • 4 Resistors to regulate the current through each LED.

Flashlight schematics design

Calculating the Resistor was also trivial. 4 AA batteries give out 6V voltage. LED operate best on around 2.5V and with a current of 40mA. So that leaves 3.5V on the resistor itself. So the resistor will run on 3.5V with 40mA. Ohm's Law gives us the value of resistors.

V = I*R => R = V / I => R = 6V / 40mA = 87.5Ω

Boards Units

Because I had not decided yet how the flashlight circuit will be mounted on a case (I had not decided the case shape itself yet), I wanted to go flexible. So I first broke up the circuit into 3 distinct units that would be interconnected with cables.

  • The batteries casing
  • The on/off switch
  • The LED board

Next, I had to design the actual boards that would host the components. I have no fancy workshop and tools which can create PCB (printed circuit boards). I had a breadboard that allows soldering parts in lines, so a bit of paper design was needed on how to create each board.


I did not want to have cables tightly soldered on boards. I wanted to be be able to break apart the bind together the board at will. So I started designing an additional board that would connect all three units together. And I decided to host this board close to the on/off switch.

Board Designs Wiring Board

The design for the LED board was a bit more complicated. I kept the resistors on the same board but on the opposite side.

Board of LED The battery casing was easy. Just bought a case that can bind 4 AA batteries together.

Batteries Casing

Jam vase

Finally had to decide on the casing for the whole flashlight. I thought to go wild thinking there, so an empty jam case seemed really fun. And then I could use this as a desktop light. Or maybe in the future, I can paint it and make it an artistic lamp 😉.

Here is the final result in action:

Jam Flashlight in dark

Costas Ioannou

I'm Costas Ioannou, a software developer, that does more than that: - miniatures - board games - art & science videos - sci-fi & fantasy.