sodbuster 1

Am using a JR S791 retract servo that only runs on 4.8V.
Am using a 6V pack for the RX supply on an AR7000 to supply control surface servos.
Am using a separate 4.8V pack run thru a switch to supply the retract servo so in case of a retract issue RX pack won't draw down or go into brownout.
2 QUESTIONS.

Will running 6V to the RX cause any issues as far as the signal to the servo?

Is my wiring schematic correct for hooking this up?

Mastertech

My Feedback: (31)

There's no good reason to do this that I can think of. Having run Retracts for 25 years I never had a problem.

Tim

sodbuster 1

Wow Tim. Tremendously helpful! Answers ALL my questions.Wonderful contribution

Will ask two more.....

Why did you bother posting to this thread if you had nothing to contribute? [:-]

You've never heard of a retract hanging up and stalling a servo causing a flight pack to draw down to nothing and then the plane crashing?
I think most would agree.....THEY have.

Lucky you in that it's never happened in 25 years.
Me? I tend to build my planes as safety minded as possible against potentialy dangerous and expensive issues.

Mastertech

My Feedback: (31)

Oh I'm sorry, I didn't understand I wasn't being helpful, I'm sorry I didn't give you the answer you were looking for.

What you have as shown will work perfectly.

That better?

Tim

lmisner

My Feedback: (2)

I've run that servo on 5 cell packs and not experienced any problems, and was surprised to see the voltage proviso on Horizon's website, but YMMV. A simpler solution would be to solder a diode in the servos + power wire, less to go wrong.

sodbuster 1

The only reason I even found out the servo only works on 4.8V is because it wouldn't operate normally on a 5 cell pack
and being it's a new servo I called Horizon before sending it in for service who informed me it should not be run on anything other than 4.8V.

I really want to run a separate 4.8V pack for safety's sake. For my part, I have seen planes go down due to a single pack
running both the flight servo's and a retract servo due to the retract servo getting stalled.
All it takes is a tire getting twisted sideways a little on the gear strut or the strut itself getting just the slightest twist.Flat spots on the stut or not. It can still happen

sebo

You really are lucky.....I had a retract hang and it drained my battery so quickly that I was fortunate to land the plane safely after one flight....no juice left for another flight.

Mastertech

My Feedback: (31)

Yes what you propose will work just fine if it gives you peace of mind.

When I ran retracts I never ran a separate battery pack. To keep the servo from "Stalling", when I made the rods to actuate the retracts I always ran a large Z bend in them to allow give in the wire to keep the servo from stalling. The servo had enough power to over ride the Z bend in case of hanging up.

On your voltage problem,

There are servo voltage "step downs" that a lot of Heli guys use that cost about $5, seem pretty robust for what they are. They use them on tail rotor servos that don't like 6v. They plug right into the servo wiring without any mods required. Pretty simple way to do exactly what you want to do if you want to go with a 6v battery.


http://www.readyheli.com/Voltage-Regulators_c_4332.html

The Western is the one I've used before.


Tim

BuschBarber

My Feedback: (2)

I have 791 servos in my H9 P47-150. They did not like 6v. They were jumpy and irratic at one end. Horizon said they were not designed for 6v and said to use 4.8v. I use a 5.1v regulator.

I like the price of the Step Down Regulator. How much current can it handle? Why is it so cheap?

sodbuster 1

Was just informed my wiring schematic will NOT work as drawn above.
Below is the correct way to accomplish this so that the different voltages utilized by the separate packs remain separated.

BuschBarber

My Feedback: (2)

Why add an extra battery, just for the Retract servo, when a Voltage Regulator is much lighter and easier to install. For that matter, why not run the entire system, like I do, at 5V. Do you really need the extra Speed and Torque that you get from 6v?

If I were running a 2.4Ghz Rx, I would want the 6v to avoid Voltage Drops that might cause the Rx to reboot. In that case, the Step Down Regulator is perfect, or even the Diode solution.

sodbuster 1

Really guys, do some of you just not read the posts/thread before you post comments to threads?
I'm really not trying to be a wiseguy here,but .....REALLY!!??


No wonder how a person can get so many posts to their name.............


done with this thread.
Been a tremendous waste of time.........

BuschBarber

My Feedback: (2)

I have followed the thread from the beginning, so YES, I have read the thread. I have never encountered the situation where a jammed Retract caused the Retract servo to drain the Rx battery. Generally, if you find the Retract is not working, you land and Fix it. I check the voltage of the Rx battery before every flight. If I see an uncharacteristic drop in voltage, I recharge and look for the cause. I use large enough Rx batteries so that even in a situation like this, I can safely make it through the flight. If you choose to use marginal batteries, then the risk is higher.

I use 2500mah two cell LiPo or LiFe Rx packs, with a voltage regulator.

I did read the other thread where A.T. posted a link to an article by Gibbs. I see how making the changes to the Y Harness allows the additional battery to power only the Retract servo.

I use one 791 Retract servo for each Retract Main.

Mastertech

My Feedback: (31)

I'm sorry you think this thread of yours is a waste of time and bandwidth.

One problem with asking advice and only wanting info posted that is what you want to hear is the fact someone else might take that info as gospel.

As good or bad as that info might be.

The info in this thread gives your way of trying to do this and the opposing view points. Each person who reads this thread from now on will have the info required to make an informed decision on which way to go.

I personally would never use a separate battery pack for retracts. Having flown them for 20+ years I've never had a problem nor have I ever seen anyone else have the problem you seem to think happens often. I've been to probably 150 pattern contests over the last 20 years with 30-50 guys flying 6 flights and never seen the failure you describe.

On your second diagram I don't see why running the ground from the second pack back to the receiver is required. A simple test on the work bench would prove out which one is correct for at least the radio system you're using.

Best of luck in your quest.

Tim

airbusdrvr

Try this diagram below. You are right, some retract servos do not work at 6V.