Re: [Paparazzi-devel] Discrete power supply for servos and autopilot

[Gareth Roberts]

Hi Tilman,

What about something like this? http://www.national.com/pf/LM/LM2678.html
Buck-boost should be ok as long as you have sufficient filtering on the  
output.

The critical stuff is all fed off the 3.3V reg anyway, which is linear.
The RC receiver will be pretty noise tolerant as it's designed to run off  
cheap BECs in ESCs, most of which are switched-mode anyway.

I've used ppz with two cells before, although it usually implies an  
aircraft so small you wouldn't want a mount like this.

As for the simplest option:
Looking at this:  
http://paparazzi.enac.fr/wiki/Lisa/M_v20#Powering_the_Board
you drive the servos seperately from the autopilot normally.
If you close the jumper JP1 you just need to connect 5V straight to the  
servo side of the Lisa (the BEC in your ESC would do fine, assuming it's a  
stock Bixler).
That way you don't need any external components or additional wiring at  
all.

Diydrones also do something similiar to your proposal w/o electronics:  
https://store.diydrones.com/Bixler_SkySurfer_Chassis_No_Pan_Tilt_p/bx-chassis.htm

Cheers,
--G

On Thu, 05 Apr 2012 10:49:54 +0100, Tilman Baumann <address@hidden>  
wrote:

> On 04/04/12 12:39, Tilman Baumann wrote:
> > What do you think. Any ideas?
> > I'm afraid I'm talking about a pure idea here. But I think I can pull  
> > it off.
> >
> > I have no great experience in RC power requirements and requirements in  
> > UAV.
> > I suppose I should separate V_SERVO and +5V for radio, GPS and  
> > autopilot.
> > How much juice should I calculate for Servos? How 'dirty' are they?
> > I'm even thinking of a Buck-Boost setup for low cell counts. Is that  
> > actually relevant to anybody?
>
> I just realized how little use that would be. I guess nobody uses less  
> than three cells. Combined voltage in of low voltage cutoff is still  
> high enough.
>
> As for DC converter modules. I could not find what I wanted at Farnell.  
> I guess I will have to build my own.
>
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