RC Model Reviews

RCModelReviews wrote:The files are now up on the website at:

http://www.rcmodelreviews.com/fpvbackpack02.shtml

tignmeg wrote:Awesome set of vids Bruce
Maybe a suggestion for V2 would be to hard-wire the BEC as a daughter board on the bottom instead of having it float around

RCModelReviews wrote:

rotorz wrote:Looks like half an FPV backpack to me..

Why is the camera being run at lipo voltage, it seems to be missing a whole regulator circuit?

It's actually run at 0.6V less than the lipo voltage -- the diode drops the 0.7V and acts as a charge-pump to reduce the amount of noise that would otherwise come from the pack. When the pack voltage drops due to the load of the FETs switching on in the ESC, it can't drag down the filter capacitor voltage because the diode switches off -- so there's a noticeable reduction in noise on the power-feed to the camera.

Most cameras are now rated at 9V-12V so this means that with a 3S lipo having a useful working voltage of about 12.6V down to 9.9V, the camera will see 12V down to 9.3V -- which is its safe operating range.

I thought the rcmodelreviews wise thing to do was run the camera from 9v or has that all changed now?

I was going to -- but found that the dropout voltage on the regulator was too high and that when the 3S lipo got down to less than 10V, some cameras would stop working -- not a good thing if you're 400 feet up and a mile away at the time

I also found that some cameras drew so much current that with the (up to) 3.6V drop across the regulator, it was risking going into thermal shutdown if the ambient temperature was over about 35 degrees C. So.. it was better to play it safe and remove the regulator because the alternative would have been a more expensive regulator with a heat-sink or a far more complex switching regulator. KISS won the day!