Lego Castle Light

At home I have a Harry Potter LEGO castle on display. During assembly I wondered how it would look if it was illuminated.

There are lighting kits, but they were quite expensive for what they are.

In the movies the castle is illuminated with torches. So it would be nice to have a similar flickering effect for the lights and also a very warm color temperature.

Fortunately mass economy has already solved this challenge with cheap electric tea lights. These are now so cheap that they are built extremely simple. There is only the plastic housing, a battery and an LED in the standard 5mm form factor.

I bought a bunch of these, because the LEDs in them already have a nice color temperature and the fake flame flickering circuit already fully integrated.
In the tea lights the LEDs are directly connected to a 3V coin cell battery. They work too with 3V from a voltage regulator.

To not have the light on 24/7 an Arduino nano was used to implement a timer feature.
The code simply turns on a GPIO at the beginning and turns it off again after a certain time.
After the GPIO turns off it can be activated again with the reset button. That’s crude but effective :).

The arduino with a voltage regulator and a transistor was placed in a 3d printed box with two rows of pin headers exposed to connect the LEDs to. Each LED was extracted from a tea light and connected to enameled wire and a female pin header.

With this the LEDs could be mounted inside the LEGO castle by wrapping the wire around posts and then just connect it to the headers.

Conveniently right next to the display area we have a multi port phone charger to charge our various gadgets. The arduino now permanently occupies one of the ports of that charger and the wire was neatly tucked behind the shelf.