Powering the LED

A project log for UV projection printer for PCBs and item marking

This tool can project UV mask and cure paint on various objects, including PCB prototypes, 3D prints, panels and household items

wojciech-adalbert-jWojciech "adalbert" J 10/08/2023 at 22:560 Comments

The power circuit is pretty simple in the current prototype:

Obviously the LED needs to have some way of current limiting. Instead of using more sophisticated control circuit, I decided to just use an off-the-shelf DC-DC converter module to match the voltage closely to the LED forward voltage, with a very small value resistor in series to limit the current (1 Ohm in this case). There will be around 0,5W loss on the resistor or so, but I find such value to be acceptable.

There is no dimming, PWM control or other functionalities, but that's not needed, as we always want to expose the image at the full power.

The circuit can use either step-down or step-up converters, depending on the power source (ex. 5V USB would need a step-up converter, while 12V PSU would need a step-down converter). An universal step-up/down would also likely be suitable (you can even use an adjustable bench PSU, but that would definitely be a less compact solution).