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HeliHobby . Ron’s HeliProz South . Century Helicopter

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Radio - Servo - Gyro - Gov - Batt > A123 setups with step down
 
 
I3DM
rrProfessor
Location: Israel

Hello guys,

Im installing an un regulated A123 pack on my X50 using JR 8717 servos.

I have a Futaba 9451 throttle servo and Logictec 6100 gyro with its dedicated servo.

How would you guys recommend doing the voltage step down for the throttle and tail servo ?
And where can i get proper step down units ?

thanks for the tips.

Team pilot for RJX, Radix, Helidirect, Logictech, ThunderPower, Fromeco
www.liorzahavi.com
05-06-2008 08:32 PM
HOMEPAGE  
 
 
Knud Pedersen
Veteran
Location: Denmark - Europa

Hi I3DM

What receiver are you using?
And what's the voltage for a new charged A123 battery?

ChopperKnud

Knud Pedersen
05-06-2008 09:36 PM
 
 
I3DM
rrProfessor
Location: Israel

Futaba Fasst 608FS

6.6V

Ill have to have less then 6.6V for:

Gyro \ tail servo
Governor \ throttle servo
Carbsmart \ mixture servo

Team pilot for RJX, Radix, Helidirect, Logictech, ThunderPower, Fromeco
www.liorzahavi.com
05-06-2008 09:46 PM
HOMEPAGE  
 
 
Knud Pedersen
Veteran
Location: Denmark - Europa

Are you uing the fromeco A123 (Ion Cube, or whats it called) battery?
What the weight for such a package, and how many amp's can it take`?

Chopperknud

Knud Pedersen
05-06-2008 09:53 PM
 
 
I3DM
rrProfessor
Location: Israel

Yes, its the Iron Corps or Iron Corps Extreme.

The extreme is genuine A123 and provides 30C contious and much more in peaks, which is MUCH more than what we need for Rx applications.

For all the info and specs please look at www.fromeco.org

Team pilot for RJX, Radix, Helidirect, Logictech, ThunderPower, Fromeco
www.liorzahavi.com
05-06-2008 09:57 PM
HOMEPAGE  
 
 
helimatt
Key Veteran
Location: Lafayette, IN

I was going to recommend you look at the Spektrum regulator with two outputs- but you mention the Carbsmart/servo so you'd need three outputs.

Can you choose a mixture control servo that will run 6V like a HS-65 or some other? I know there are options.

Fully charged, the A123 2S pack should be more than 6.6V, isn't it 3.3V per cell nominal? Not sure myself.

Otherwise, there are several "BEC's" that will regulate down to 5V and carry enough current just for tail, throttle, and perhaps mixture control. 3A should be plenty.

(Don't run the 6100G servo on more than the rated volts- I learned the hard way!)

Never, ever, ever, ever give up.
05-06-2008 10:17 PM
 
 
I3DM
rrProfessor
Location: Israel

How much did you run with the 6100G ?
I have it on 6V regulated so far without problems.

I think ill use direct 6.6V for everything (which is like a charged 5 cell Nicd) and an Align 5.1 step down for the tail servo.

Team pilot for RJX, Radix, Helidirect, Logictech, ThunderPower, Fromeco
www.liorzahavi.com
05-06-2008 10:34 PM
HOMEPAGE  
 
 
ferincr
Senior Heliman
Location: San Jose - Costa Rica

I'm running 2S A123 on my Raptors direct with just the step down on them
In one of them I have the Logitech 6100 gyro and according to Logitech specs it should work at 3.7v-5.5v so I have the step down before the gyro which brings the voltage (according to the gyro's LCD) to ~5.7v
Jusy my $0.02

Intelligence chases me, but I'm a lot faster! Fernando
05-06-2008 10:57 PM
 
 
Jeff polisena
Veteran
Location: westpalmbeachflorida usa

http://www.heliproz.com/prodinfo.asp?number=154021
This is what I use just for gyro and run servos straight from receiver
you can use on throttle also if needed


I dont know how to fly just how to not crash !!!!!
05-07-2008 12:23 AM
 
 
I3DM
rrProfessor
Location: Israel

ferincr, that sounds like the ticket !

Team pilot for RJX, Radix, Helidirect, Logictech, ThunderPower, Fromeco
www.liorzahavi.com
05-07-2008 03:25 PM
HOMEPAGE  
 
 
helimatt
Key Veteran
Location: Lafayette, IN

A123 batteries are 3.6V per cell fully charged, but they can be charged to 4.2V per cell (though repeatedly doing so might harm the cell).

So, the 2S pack is charged 7.2V normally. Stepdown .7V and you get 6.5V to the gyro and/or tail servo. Ouch.

Am I missing something there? If not, you'd be in danger of over voltage to the tail servo.

If the step down is before the gyro, and it reads 5.7V, then you're pack is around 6.4V under whatever load you've got on the system at the time. 5.7 is still over spec but not to much. However, if that's not a fully charged pack then you would be running farther above the spec allowable V for the 6100G.

I was flying a 5-cell NiMh pack with a single stepdown on the 6100T/G. Worked for a while... my mistake or sloppy engineering, so I paid for it. I put in a regulator and 2S lipo, all's well.

That Spektrum regulator seems just the thing.

Never, ever, ever, ever give up.
05-07-2008 04:46 PM
 
 
ferincr
Senior Heliman
Location: San Jose - Costa Rica

I use an Hyperion EOS 610i to charge/balance these packs and top charged I never get more than ~3.45v per cell.
I just checked it with the batt fully charged and the Logitech LCD shows 5.9/6.0v (i guess it's a bit on the high side) I might add a second Diode to it and see how it looks.

Intelligence chases me, but I'm a lot faster! Fernando
05-07-2008 05:25 PM
 
 
I3DM
rrProfessor
Location: Israel

I just made my own step down with a diode:



If i understand correctly an A123 cell charges up to 7.5V but as soon as you give it a slight load it will settle down to 6.6V.

Can anyone confirm this ?
ferincr, how long does it take until you see 5.7V or less on ther LCD ?

Team pilot for RJX, Radix, Helidirect, Logictech, ThunderPower, Fromeco
www.liorzahavi.com
05-07-2008 05:43 PM
HOMEPAGE  
 
 
ferincr
Senior Heliman
Location: San Jose - Costa Rica

It looks like it might take around 10/15 minutes, but I just added another RL205 I had laying around and the voltage on the gyro now is ~4.9/4.8

I'll leave it on for a while to see how it progress, I put a bit of load on the servos but it doesn't seem to affect it.

Sorry for the empirical methods but I only passed electronics101 and I don't have any sophisticated equipment

Intelligence chases me, but I'm a lot faster! Fernando
05-07-2008 05:58 PM
 
 
I3DM
rrProfessor
Location: Israel

Did you ever check the pack voltage to see how it behaves when fully charged ?

Also, which servos are you using ?

PS - i asked Logictech, and they said the gyro has no problems running on 6.6V so you could always put the step down in between the tail servo and gyro if you choose to.

Although your method sounds good, im a little concerned if once the pack voltage drops you will be seeing 4.5V - 4.6V on the gyro, which is probably starting to get low.

I hear there ae 0.2V diodes also, so wiring a couple (0.7+0.2) might give about 5.7V which might be perfect.

Team pilot for RJX, Radix, Helidirect, Logictech, ThunderPower, Fromeco
www.liorzahavi.com
05-07-2008 06:20 PM
HOMEPAGE  
 
 
ferincr
Senior Heliman
Location: San Jose - Costa Rica

Update

With the two diodes in series the voltage is (as I said before) right on spot, but when I put continuous load on the servo (force it a bit with my finger) after some time (a minute or so ) it get uncomfortably hot for my peace of mind so I think I'll leave it as it was.
After 10 or so minutes the voltage shows 5.7v at the gyro and when I load the servo, drops to around 5.5

Intelligence chases me, but I'm a lot faster! Fernando
05-07-2008 06:21 PM
 
 
ferincr
Senior Heliman
Location: San Jose - Costa Rica

Quote 
PS - i asked Logictech, and they said the gyro has no problems running on 6.6V so you could always put the step down in between the tail servo and gyro.
Thanks, that sells it.
I leave as it is (with the step down before the gyro) anyway it doesn't seem to be any benefit on running th gyro at higher volts and it may help dropping few more .000v before entering the servo.

Intelligence chases me, but I'm a lot faster! Fernando
05-07-2008 06:24 PM
 
 
I3DM
rrProfessor
Location: Israel

ferincr, you could always add 1 more diode between the servo and gyro, to give an additional 0.7V drop.

I dont see the direct connection between wiring 2 diodes and heating up, since both will still be having the same current run through and same voltage drop.

PS - at the moment i have quite a few flights on my 6100 combo regulated at 6.0V and all seems to work perfect so far (probably 30 HARD flights or so on my X50) so the one diode idea sounds OK to me.

which cyclic servos \ Rx do you use ?

Team pilot for RJX, Radix, Helidirect, Logictech, ThunderPower, Fromeco
www.liorzahavi.com
05-07-2008 06:25 PM
HOMEPAGE  
 
 
I3DM
rrProfessor
Location: Israel

By the way, is this a step down or a regulator ?

http://www.helidirect.com/product_i...roducts_id=4173

Team pilot for RJX, Radix, Helidirect, Logictech, ThunderPower, Fromeco
www.liorzahavi.com
05-07-2008 06:30 PM
HOMEPAGE  
 
 
ferincr
Senior Heliman
Location: San Jose - Costa Rica

Sorry forgot the servos part.
I'm running this setup:
Rx: Futaba 138 DP PCM
3x S9351 Cyclic and collective
1x S9252 Throttle
1x Hitec HS81MG on the carbsmart
Logitech LTS 6100G on the rudder

Intelligence chases me, but I'm a lot faster! Fernando
05-07-2008 06:32 PM
 
 
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Radio - Servo - Gyro - Gov - Batt > A123 setups with step down
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