I wanted the ability to dim or flash some static 12V LED strings (example).
These dimmer modules are a whole $1 each on eBay (including postage) !
They are supposedly rated for 12V – 24V input and up to 12A output.
I’d probably only trust them for a few Amps, but haven’t tested them thoroughly yet.
The module does seem to remember the last used mode which is good.
Trim the supplied leads back, strip and tin the ends.
Solder a male 2-pin pigtail to the DC input and a female 2-pin pigtail to the output.
The MODE button offers a few different fading / flashing effects.
The LIGHT button puts it into plain dimmer mode.
The middle button selects the flashing rate or dim level.
The dimming range and effects are limited, but not bad for $1.
Here’s a video showing some of the effects it can do: