Here is a gif showing it in action, once the motion is detected, the strip slowly lights up directionally from bottom to top, how is this achieved? I can't seem to find how this is done: Looping GIF link
Electrical Lighting LED Stairs Design – Achieving a Stairway Chaser Effect with LED Light Strips
designelectricalledlightingstairs
Related Solutions
You can get any number of configurations of AA battery holders. Mouser Electronics, an online electronics distributor has a whole page of them in their catalogue at AA Cell Holders Page from types that can accommodate 1 cell all the way up to 10 cells. Here are a few representative pictures of the ones available.
These are available with solder tabs, wire pigtails or snap fitting connections.
The specifications for the current power pack (transformer) offered by Malibu says that it is Not for use with dimmers. Older versions listed on their site also say the same thing.
While some of the earlier transformers from that manufacturer may differ, it doesn't look promising unless you swap out the transformer for a different brand.
Best Answer
Here is the website that the video came from.
tinker-fun.com/DigitalLEDStairlighting
Note that this DIY project requires electronics and software knowledge. The website has fairly detailed hardware instructions. The designer has not posted the full software yet. Pieces of the software are available from various open sources.