This tutorial shows the functions of the buck converter (step down) with tree trimmers. It also reveals the secret of the middle trimmer and it tests the efficiency of such a converter in different situations.

Electronic Load Module: http://s.click.aliexpress.com/e/6QNj2zb
(mine is no longer available)

Buck converter (tree trimmer): http://s.click.aliexpress.com/e/6MnyNfe

Buck Converter (1 trimmer): http://s.click.aliexpress.com/e/urfA2vb

LM2596 datasheet: http://www.ti.com/lit/an/snva532/snva...