handlaunch lipo pack 7.4 to 5v regulator

[wwang]

I have been a HLG guy and flying 4x N type cells for hand lauch. I just had a N cell pack go and was looking at trying to get more durration out of a 2s LIPO pack.

I was thinking that they make simple 5V regulators ready to go, but have not seen any for this other then FMA and that looks huge.

Has this been explored already and what should I need? I don't need much reminder to stop, I fly by time anyway. So if I get a couple of small 2s packs, I can fly a LONG time. But I know I can take 7.4V and put it into a RX. Can anyone help me get to 5V from 7.4v that will work?

Thinking about this, does someone have a booster circut to 5V for 1s lipo or is the 7.4v voltage limiter a better choice?

[simingx]

A low dropout linear regulator such as a LM2940C would work, as it'll work all the way down to just above 5V (which you shouldn't be doing). At the currents a HLG needs, the efficiency isn't an issue.
Remember to put a capacitor across the output (as in the datasheet) otherwise the output will be unstable and shoot up to the input voltage. Measure output with a voltmeter first!

[AndyOne]

Wwang,

This subject has come up before, see the following thread...

http://www.rcgroups.com/forums/showthread.php?t=238537

Andy.

[DNA]

A silicon diode has a voltage drop across it of about 0.6v to 0.7v. If you put three diodes in series in one of the battery leads, you will decrease the voltage by about 2 volts.

[Dan Baldwin]

A silicon diode has a voltage drop across it of about 0.6v to 0.7v. If you put three diodes in series in one of the battery leads, you will decrease the voltage by about 2 volts.

The problem with that is that the diodes will maintain that voltage drop as the batteries run down, so at the end of charge (6 volts) you will only have about 4 volts after the diodes.

Dan