A Construction Article
I was chatting with an RC friend the other day and we started talking about how hard it is sometimes to see things especially when they get to the edge of our visual field. He happens to be an fpv pilot. So, as engineers, we always try to solve the problem.
One suggestion was to put a beacon on the aircraft, sort of like those very strong blinking lights you see for bicycles. Of course, you could buy one of those and take it apart, but that’s no fun. So, we decided to build one. We had both seen some of the very powerful LEDs at Anchor Electronics, 0.5watt, which seemed to be the solution. We agreed on a basic design, then each of us did some tweaks; pretty much the same result, but each path was a bit different. This article shows how to build the Tim version.
Below is a pic of the finished board with a pass thru deans connector. You can see from the size of the deans how big the beacon is.
Full up Beacon
Beacon board alone
Above is a closeup of the board, it’s 1.4” x 0.8”.
Below is a pic of the relative layout to make the hookup easy.
Below is the schematic which uses a classic 555 timer and a dual FET to drive the LEDs. The LEDs are driven at about a 25% duty cycle and about 2x power rating. I used mostly surface mount components to make the board size small.
Further details and some alternatives
1. The described schematic values using dual FETS drives each led at about 1w, or about 450ma, 2x rated power.
2. You could change the 555 type and drive the leds directly from a bipolar 555. The CMOS version used here cannot deal with this level of current. The bipolar 555 (older) can source ~200ma which is pretty high but even with a single led the brightness would be less.
3. You could use a dual p channel FET and alleviate the 3906 transistor.
So, if you’re looking for a short and interesting little project, you might build a beacon.