Project History

After making the STEPS power supply boards, the main complaint I got was the relatively high cost to build it. (It's about twice as expensive as the popular Elpac WM080 linear-regulated wall wart.) For a long time, my standard response to that complaint was to recommend the Velleman K1823 power supply kit. It didn't perform as well as a STEPS, but it was reasonably close, and the cost was a lot lower.

Over time, though, I became more aware of the flaws in the Velleman design. First, its output voltage was not very stable. At its best, the Velleman's average noise level was less than 5 dB over that of the STEPS, but looking at the noise on a scope, you'd see much higher transients. (I attribute this to poor layout.) Second, the kit is billed as capable of putting out up to 35V, but some of the parts shipped with the kit will actually break down beyond about 28V. Third, the board is missing the protection diodes recommended in the LM317 datasheet. And finally, the circuit board is at least twice the size that it has to be.

After my experience with the STEPS, I knew I could do better on all fronts. (See the STEPS history page for the full saga.) I went ahead and designed the board, ordered prototypes, and on testing found that it was indeed free of all the Velleman's flaws relative to the STEPS. Thus assured that it was a useful design, I went ahead and made production PCBs.