Introduction: UMAkers Lantern
We're a group of students of the University of Málaga (UMA). This project is part of the subject 'Creative Electronics', a BEng Electronic Engineering 4th year module at UMA, School of Telecommunications (www.etsit.uma.es).
Our project consists of a strobe light. Details about the components used and the process followed will be outlined at the following steps.
Step 1: Preparation
- Resistors (50Ω and 10kΩ)
- Potentiometer 10kΩ
- Power transistor BDX
- SMD Led 50W
- Led driver (240Vac - 50Vdc)
We bought the SMD led with its driver through Amazon (here).
- ATMega 328p
We're gonna need two Arduino boards (one of them with removable microcontroller)
- Pre-drilled Prototype PCB
- DC-DC Buck Converter (LM2596)
- Heatsink and thermal paste [optional]
On the image on top of this step there's a component that it's not used on this first version of the lantern. This component is an accelerometer, we are planning to include it on future versions to control the blink of the light with the move of the hand instead of spinning the potentiometer.
Step 2: Schematics & Explanation
We have chosen the BDX transistor because of the high DC current gain value (beta) because we must control the saturation and cut-off states of the transistor just with the current of the microcontroller (the collector-emitter current can reach values of 1A).
Our project is designed to control a circuit of high voltage values with a microcontroller which provides low current values through the digital outputs.
We have placed a DC-DC reductor (using the output of AC-DC converter) to power on the microcontroller. In order to control the duty cycle of the PWM (that controls the blink of the light) we have used a potentiometer connected to the microcontroller.
Step 3: Codding and Uploading the Code
To upload the code into the microcontroller, you can follow the next steps: (from the official arduino webpage)
- Download the hardware configuration archive (here).
- Create a folder named "hardware" in your Arduino sketchbook folder.
- Move the folder downloaded previously to the "hardware" folder.
- Restart Arduino software.
- When you run the program again, you should see "ATMega 328 on a breadboard (8MHz internal clock)" in Tools>Board menu.
- Burn the bootloader (you should only need to burn the bootloader once).
- Select the board and serial port from the Tools menu.
- Wire up the Arduino board and microcontroller like this.
- Select ATMega 328 on a breadboard (8MHz internal clock) from Tools>Board.
- Select Arduino as ISP from Tools>Programmer.
- Run Tools>Burn Bootloader.
- Upload the code: once your ATMega 328p has the Arduino bootloader, you can upload programs.
- Remove the microcontroller from the Arduino board.
- Wire up the Arduino board and microcontroller as shown on the next image.
- Select "ATMega 328 on a breadboar (8MHz internal clock)" from the Tools>Board menu
- Upload as usual.
Step 4: Let's Solder the Parts!
- We start soldering the transistor and the resistors.
- Introduce the microcontroller in the pre-drilled PCB and cut the rest of tracks.
- Let's solder the microcontroller.
- Solder the potentiometer close to the analogically input of the microcontroller. Add the necessary wires to place the DC-DC reductor module.
- Solder the DC-DC by the other front of the PCB.
- Take the SMD led (it is optional to place a heatsink, we have re-used one of a 3D printer).
- Solder the wires that connect +Vcc and Ground (GND).
- Once each of the parts have been soldered, we have decided to place all the system in an old disco bulb so that the designs remains compact.
- Don't forget to solder the Led to Vcc and the transistor (we have used an electrical connector). Remember to solder the connection of the DC-DC converter (pay attention to the schematics).
- We have connected the wires from the Led driver to get some comfort for its use. The ends of the copper wires have been tinned and we have connected both ends. To get a better result and avoid short-circuits,we have used thermal paste.
- We have made two holes in the disco bulb so that we can get the wires out and control the potentiometer better.