Servo voltage explanation please...

[OhDonPiano]

Could someone with some patience, please explain the servo voltage options for a 600N?

Now, to make things simple, lets assume I am interested in the 600 NSP package, which includes the Align 2 in 1. My assumption is that this is similar to a BEC that is included in an ESC of your electric friends? (i.e., this is the part responsible for regulating the voltage from your battery pack to the voltage of your servos)

So it seems there are 2 voltage paths to choose from, 6v and 8v, is this correct?

How do you choose between the two? ( i.e., is there a programming choice on the 2 in 1 to choose 6 or 8 volts?)

Where does a VR5203 (Spektrum Regulator) fit into this mix?

How does all of this work with tail servos? Are most people who run 8v, running 8v on the tail servo as well?

I am massively confused...

I am thinking about ordering electronics prior to ordering my 600 kit simply for budgeting concerns...

I am currently considering 3x 8717 on the cyclic and 770 + 8900G on tail... do I need the VR5203?

[george0079]

"I am currently considering 3x 8717 on the cyclic and 770 + 8900G on tail... do I need the VR5203?"

Yes, or something simalr to it, to run the gyro/tail servo and the throttle.

"So it seems there are 2 voltage paths to choose from, 6v and 8v, is this correct?"

If you plan on using the 2in1, then no. It runs on 5.8V

[george0079]

Every servo has a voltage rating. These ratings are based on nicad battery packs (Kind-of old school). 4.8V is a 4 cell nicad, and 6.0V is a 5 cell nicad.

8V is a new lipo thing that is gaining popularity rather fast.

[OhDonPiano]

Thanks for the general info... I found a post in another thread which basically explains the 8v setup using a schematic here (http://www.helifreak.com/showthread.php?t=70815).

Basically for 8v, you power the Rx directly by a 2S Lipo and use a regulator like the Spektrum dual regulator for all the stuff that needs to be stepped down to 6v. The schematic explains this better than my explanation ever could...

For a 6v setup using the Align 2 in 1, my assumption is that you simply apply power to the 2 in 1 using a 2S lipo and the Align 2 in 1 BEC outputs at 5.8v (which I guess is considered 6v) - this powers the Rx (servo bus), and as long as all of your servos are spec'd to support 6v you are good to go....

If this is not correct, please feel free to correct my assumptions...

[george0079]

the only thing you left out was the stepdown for the tail servo (If using the 2in1).

[invertmast]

the only thing you left out was the stepdown for the tail servo (If using the 2in1).

which is not needed IF you are using a tail rotor servo that is spec'd to work on 6volts.

[OhDonPiano]

Thanks... I think I have a much better understanding of the servo requirements now, and it looks like both of the tail combos I am looking at (770+8900G and 611+9256) are 4.8v only so I will be sure to include a regulator in my package...

Any bad experiences with the cheap Align 5.1v step down regulator?

[invertmast]

no bad experience. just be aware that its not a regulator, it only drops the voltage about .7volts. Its basically their to allow you to run 6volts to everything, and then put it between the gyro and TR servo and get 4.8-5v roughly

[OhDonPiano]

Ok... so I hate to be like that gnat that just won't go away... Maybe I should start a new thread for this, but will try it here first...

How do you determine your total power needs of all your servers?

i.e, assuming I am powering everything through the Align 2 in 1 - which is rated at 6 amps? I have seen several posts where people claim that the Align 2 in 1 is not powerful enough for a setup similar to what I am interested in (3x 8718s on cyclic + 770 + 8900G tail + DS821 throttle). How do I add up the max current load of stuff powered by the 2 in 1?

Yes, these are the kind of details you obsess about when there is nothing on your workbench to build or take apart :)

[george0079]

First of all, I STRONGLY adise against using the DS821 on any part of a nitro heli. Even the throttle. There have been many reported failures. And the manufacturer web site even states to not use them on nitro bird 50 size or larger.

As for the 8717's... There has been alot of success for people using them with the 2in1. But there have been problems, as well. The 8717's draw enough power to put the 2in1 right at the edge of it limits. So if you're donig hard 3D, or your mechanical setup has ANY binding, it can cause a brown-out

[chosen69]

You can use the laws of physics to calculate theamps drawn. i.e - I (in amps) equals P (in watts) divided by U (voltage). Now you need to know how many watts your servo's produce under full load which I couldn't find out for the 8717's. But let's assume they produce between 10-12 watts under full load - divided by 6V equals around 2 amps per servo. Those can just be added up for all servos, governors etc.
This should give you a close idea of what your regulator/wires/connectors should be able to handle.
In my case I have 4x 8717's and the 770/8900 combo on the 600n plus the multigov and assume that unless you have a binding servo (which increases the watts exponentially) you should never draw more than 6amps because running those servos under 6V they will never be anyway near to their max load. I'm not really counting the throttle 8717 because it has no load at all. You could hook up a voltmeter and move the servos while grabbing them and simulate the load but it won't be the same. I personally instead of the 2 in 1 use this one :

http://www.readyheli.com/K10382A_6A_External_BEC_w_5_1V_Two_way_Step_down_p/k10382a.htm

and haven't had any problems plus it comes with the stepdown for your tail servo, only difference to the 2 in 1 is that you lose the comfortable glowplug ignitor. The only drawback is that it will get warm if not hot which is what it's designed to do. If you want to be absolutely safe get a switching regulator like the duralite rated for 7.5 amps and it won't even get warm.
http://www.duralitebatteries.com/flight/accessories4.php

Either way I don't think you can go wrong with the 2 in 1 and the price is acceptable. Just don't get the combo with the align battery as they are not known to be the brightest crayon in the box. I personally use a flightpower 3000mah 2S2P with deans connectors.
Sorry for being too long, again. Just my 2 cents.

[OhDonPiano]

Lots of good info... Thanks for all the info everyone! (and thanks for the warning on the DS821 george).

Lots to digest. Once my final decision is made, I am sure I will not be able to hold back the obligatory "Just purchased my 600N" post... or maybe I'll wait till the build is done and show pictures... anyway, thanks again. This place is awesome!