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Flying 3S and 4S on the same frame
#1
Hi Folks....

I haven't seen this covered anywhere and I apologize if this rather elementary question has been asked and answered.  I have a ZMR 250 frame with some version of the Overdraft PDB.  I say "some version" because I haven't seen one that looks exactly like it....very very close, but not exactly.  Anyway, I would like the capability of running either  a 3S OR a 4S Lipo based on which Props I want to use.  Assuming I have a 12V FPV cam I would need to run a step up PS to make sure the 3S gets 12V to the cam.....right?  Is there a simple way to isolate power from the two different sources (for 3S) or step down (for 4S) so that the correct one feeds the cam and I do not have a conflict regardless of which Lipo I use?  Or am I making this way too complicated?  I would appreciate any insight anyone might have.  Thanks guys. : )
#2
(03-08-2016, 01:58 PM)sirdude Wrote: Hi Folks....

I haven't seen this covered anywhere and I apologize if this rather elementary question has been asked and answered.  I have a ZMR 250 frame with some version of the Overdraft PDB.  I say "some version" because I haven't seen one that looks exactly like it....very very close, but not exactly.  Anyway, I would like the capability of running either  a 3S OR a 4S Lipo based on which Props I want to use.  Assuming I have a 12V FPV cam I would need to run a step up PS to make sure the 3S gets 12V to the cam.....right?  Is there a simple way to isolate power from the two different sources (for 3S) or step down (for 4S) so that the correct one feeds the cam and I do not have a conflict regardless of which Lipo I use?  Or am I making this way too complicated?  I would appreciate any insight anyone might have.  Thanks guys. : )

Overthinking it a bit really.

Make the quad from the start as a 4S build, buy a HS1177 FPV cam as they support 7-22 volts and almost all mini vtx's now support the same. so all you would need is 5 volts for the Flight Controller.

Or, as you say, assuming you only have 12 volt FPV cam just make sure your PDB has a 5 volt and 12 volt output. 5 volts for the flight controller and 12 volts for the Cam and vtx.  While you are at it, it is really good practice to add a line filter to your FPV gear (FPV cam and VTX).

So, if you prepare the quad as 4S it will run 3S without a hitch.
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#3
Thanks Biggles....I do tend to make things a little more complicated then they need to be sometimes. I guess my concern was that since the 3S does not give 12V to begin with I would need a step up if any of the equipment took 12V. However, as you say I can get a cam that falls within the full voltage of each and my problem will go away. I am awear of the need for a filter and I'll be sure to put one in line to the cam. Thanks again! : )
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#4
note, that most voltage regulators on PDBs are step-downs, that means that if You use 3s, your 12V reg will output lower voltage, ie. 10V on full charge. Not a problem for wide voltage equipment though.
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#5
What's the reason for you to run 3s and 4s at the same time? I would just stick with one hehe Big Grin

If you think 4s is too powerful and like to learn on 3s first... No need either... Just use small pitch props, you can achieve the same effect
Don't be a LOS'er, be a FPV'er :) -- My Fleet
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#6
Well the reason, in my convoluted way of thinking, was that 4S would give me the resources to use a more aggressive prop and still maintain a reasonable flight time with at least some measure of increased performance?
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#7
(03-08-2016, 04:39 PM)sirdude Wrote: Well the reason, in my convoluted way of thinking, was that 4S would give me the resources to use a more aggressive prop and still maintain a reasonable flight time with at least some measure of increased performance?

Just stick with 4S and don't bother with both Smile
efficiency is more down to motor/props combo... than the cell count of LiPo...
Don't be a LOS'er, be a FPV'er :) -- My Fleet
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#8
Well that suits me...simpler...and I am all for simple! Thank you, one and all! : )
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