I recently bought the following from eBay:
http://www.ebay.com/itm/221255588116
The problem I'm having is that if I connect the four LED strips end-to-end, each one becomes more and more dim until the fourth strip is barely on. Obviously I want them to all be as bright as eachother...why is this happening? I'm not using an Arduino to control them yet, just the basic controller, but I have an Arduino all ready to go to control them as soon as I figure out what's wrong.
If you plug you toaster into a 200 foot extension cord you wont get very brown toast.
You are experiencing voltage drop over the very long length when using 4 strips driven in series.
You will have to drive them in parallel.
12v x 3
36v you'd have to supply in order to keep the same brightness..
Really ?
The strips are flexible printed circuits so the power and ground wires are pretty thin and have significant
resistance - you would ideally connect each strip separately directly to the PSU (at both ends)
If you want them in a long line then one compromise is to supply power to both ends of the string
of four (assuming the ends are near enough to each other). Use suitably thick wire between PSU
and strips if any length of run is needed. Then the middle sections will be partially dim.
They could be connect the four strips in series and run from 48V, so that each strip's positive supply goes to
the next's negative supply, and the last strip gets 48V to its positive supply and the first 0V to its negative.
This will give the most even distribution of voltage/brightness, but curcially relies on the strips being
identical in current drain at 12V. Also you can't control them separately if in series.