Tuesday, December 20, 2016

Board Built and (mostly) operational!

My boards came back from OSH Park with no issues, and they look good. Everything is gold-plated, and solderability is excellent. The only issue (not really an issue) were the tabs left over from where the boards were broken out of their larger panel. A quick hit with a file took care of that no problem.

The board consists of two power converters - one a DC-DC device that powers wireless sensor pods (on the left by the fuse.) The other is a simple three-terminal regulator that provides a somewhat dirty 5V to engage the alarm relay. There are two supplies, as the dirty supply needs to fail when the AC is removed. This causes the relay to fall, and a remote sensor (powered by the DC-DC converter and a battery) sends an alarm to a remote system. The DC-DC converter runs off the battery and powers sensors during an outage.

The three-term device doesn't get a heatsink, as there is only about 50mA of current draw. The DC-DC converter is rated for 500mA, and has a load of about 150mA.

The back of the board (which I didn't take a picture of for some reason) has the remaining components - a rectifier for the alarm side (as it runs directly from the input transformer) and some filter capacitors. I actually didn't put enough filtering on the board, so a radial capacitor was added. As I'm making a second run with a few more functions, the capacitor will be changed to surface mount and placed on the board.

In all, my first personal project PCB turned out pretty nice, and I've decided to add some extra stuff like a low battery monitor and cutoff circuit to the next rev.