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2014/07/06 converting a minimOSD to 5V, adding a heat shield and overvoltage protection
π 2014-07-06 01:01 in Rc
After reading on the voltage regulator for 12V on the minimOSD runs too warm and can die on some versions, or generates too much noise in the 433Mhz range which is bad for LRS radio control, I figured I'd do the 5V conversion.

Initially the idea is to send 5V from the APM side to the analog side. To avoid ground loops and burning the video chip, I also did the recommended ground connection on both sides:

Next, I added some small heatsinks on both chips, it's especially important for the video chip that can overheat and die, bad if you're flying when that happens :)

Now, once you power the analog side from the 5V rail, it's not regulated and the video chip tends to die by the time votlage reaches 5.3V, so I added a 5.1V zener diode to get rid of possible voltage spikes. With that, while my first OSD died after minimal use, the 2nd one has worked great so far:

But one last thing I did was to realize that since I was powering my camera with 5V too and my transmitter was already providing a perfectly good 5V signal, I might as well poewr the entire thing from the transmitter side. For that, I added another wire going across with a jumper to let me pick whether 5V comes from the analog side, or the APM. Another thing to note is that powering the OSD from the APM internal power works, but is out of spec if you're also powering the video chip, so it's another reason to just power all of the OSD from its analog side and the video transmitter power supply.

5V power to the digital side from the analog side
5V power to the digital side from the analog side

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