Super using 4PL and 7980s

[KC_JoNeS]

Well, my junk is wired, and I am using the preset steering mixing for the 4PL to control the servos. But, I am getting some glitching occasionally when in 4 steer modes (either crab or 4 steer).

I have my BEC set at 7.4 volts, which I was a little concerned about, as the Futaba R2104GF shows operating voltages from 4.8V to 6V.

Here is my wiring diagram currently.



As you can see, I have the ESCs plugged into channels 2 and 4, which works fine. I have the steering in 1 and 3, and that is ok too. But, the BEC is plugged into the B slot of the RX. When I am in either 4 steer mode, the power seems to drop out on me. I have to assume it is due to the higher voltage on the RX. But, I would like to be sure.

Do I have to run a single BEC to each servo, as opposed to just powering the RX as a whole? I prefer this method as the wiring is a whole lot cleaner, but I want this thing to work as well.


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EDIT: Here I am a couple hours later, and I have taken the good advice offered and wired the system differently...adding another BEC to the mix. Here is the new diagram. It works perfectly now. Thanks fellas!



Casey

[KC_JoNeS]

I should also add, this power drop out occurs under no load. I do not have the wheels and tires mounted.

Casey

[michael]

yes two bec run directly to the servos would work and also a pro cc bec would work too

[michael]

Does it happen when your sending signal to both servos?

[KC_JoNeS]

Originally Posted by michael

yes two bec run directly to the servos would work and also a pro cc bec would work too

Well, keep in mind, a single 10A BEC is strong enough for several servos. 2 7980s under no load will not require 10A. So, this must be an RX issue.

Originally Posted by michael

Does it happen when your sending signal to both servos?

yes, it only happens when sending signal to both at the same time. There is no issue when in front steer only mode.

[shelby]

Your your futaba rx didn't burn up at 7v? Because I would like to bump my bec up to 7v, but my futaba rx only goes up to 6.

[KC_JoNeS]

Originally Posted by shelby

Your your futaba rx didn't burn up at 7v? Because I would like to bump my bec up to 7v, but my futaba rx only goes up to 6.

I have only plugged it into a battery 3 or 4 times to dial everything in. Nothing is burned up yet. But, it sucks that this RX is tolerant of only 6V.

[michael]

had the same prob with mine running two jr8711,when I was sending signals to both serv it would loose signal for a sec and the red light on the rx would come on for a min and then go green.

[KC_JoNeS]

Originally Posted by michael

had the same prob with mine running two jr8711,when I was sending signals to both serv the red would loose signal for a sec and the red light on the rx would come on for a min and then go green.

Yes, that is happening to my RX as well.

Casey

[michael]

almost certain its a bec issue

[KC_JoNeS]

Originally Posted by michael

almost certain its a bec issue

I can appreciate that...but it is not under load. It is just sitting on my desk with no wheels and tires.
The first test I can do to verify is to unplug the BEC, reprogram it to 6V and try again. If it continues to have the same issue, it is the BEC.

I will report back after the test.

Casey

[michael]

what you mean its not under load,it happens when your sending signal to both servs right?

[SVEN]

One thing I never do, is have any servo power running through the RX. This eliminates a lot of headaches trying to isolate electrical issues.

I have a regular CC BEC running to each of my servos. The BEC and servo are plugged into the 2 female plugs of a Y harness with the male going to the RX. The male plug of the Y has the RED wire removed to isolate the power from the RX.

Basically, I run the BEC's to the servos, not through the RX.

Since there are 2 ESC's, I pull the red wire from one of them going to the RX. So, the only power going into the RX is from a single ESC.

This has been the easiest setup I have found. It may sound complicated, but it actually simplifies everything, keeps components from killing each other, and reduces glitching.

It may not seem like it just going by the specs, but with 2 7980's you will want to have either a CC BEC Pro or 2 regular CC BEC's.

I have been through my far share of CC BEC's to know.

[KC_JoNeS]

Not under load...meaning there is nothing for the servo to push around except some knuckles not mounted to anything.

So, I updated the BEC to 6V, and tried again. It still does it when in 4 steer mode. And, also, I seem to be mistaken before. The problem does not occur in both modes, ie crab and 4 steer. The problem only occurs during 4 steer. That is sort of curious.

Casey

[KC_JoNeS]

Originally Posted by SVEN

One thing I never do, is have any servo power running through the RX. This eliminates a lot of headaches trying to isolate electrical issues.

I have a regular CC BEC running to each of my servos. The BEC and servo are plugged into the 2 female plugs of a Y harness with the male going to the RX. The male plug of the Y has the RED wire removed to isolate the power from the RX.

Since there are 2 ESC's, I pull the red wire from one of them going to the RX. So, the only power going into the RX is from a single ESC.

This has been the easiest setup I have found. It may sound complicated, but it actually simplifies everything, keeps components from killing each other, and reduces glitching.

It may not seem like it just going by the specs, but with 2 7980's you will want to have either a CC BEC Pro or 2 regular CC BEC's.

I have been through my far share of CC BEC's to know.

Fair enough. What you said is not that complicated. Makes sense. And thanks. I guess it is time to rewire.

Casey

[michael]

you are correct you servos are not under load but your bec is

[kurtus]

The r2104gf rx is actually rated for 3.5-8.4v so you are just fine with the 7.4v your running at, http://www.amainhobbies.com/product_...l-Receiver-4PL, http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXACWW, confirmed on 2 reputable sites. I'll be running mine on 7.4 once my 7980 shows, been running my 5955tg on 6.6v for months with no issues. I vote pro bec, you should be fine running that the way you want too

[ax-10 crazy]

I believe your problem is to do with the bec. With my 7980 and normal cc bec the bec gets warm just from wiggling the wheels back and forth. So I assume to 7980's would make it worse. Running a single bec to each servo should fix your problem or a bec pro.

Remember as the voltage you set on the bec increases the amount of amps it can supply goes down. I also read that a single 7980 requires 9+ amps during a load which at 7.4 volts a single cc bec would not work.

[War Pig]

I completely re-wired my Willys Scale rig with a Pro BEC running the 7980 front and 7950 rear at 7 volts. I also have a 10 amp BEC powering the receiver (at 6.1 volts) that the winch is plugged into. I just installed a Tekin RS Pro and had a bit of a glitch myself. As I was getting into the throttle the servos would twitch (front and rear). After talking to a couple of friends I added a ground loop so that all the ground wires were tied together, and I also removed the orange signal wire from the 10 amp BEC to the receiver just for kicks. It cured my glitch and things seem to working quite nicely now.....just goes to show that the simplest little thing can upset all that electricity flowing to and from the receivers and servos. I think you'd be best to wire your servos directly to the BEC.....that's alot of amps and voltage to be running through your receiver. Good luck.

[kmnss]

Although I think the problem lies in the wiring, and the single BEC for two massively amp hungry servos, there is something else to consider. Sven's trick will eliminate this, but....

The RX may accept up to 8.4V, but only distributes 4.8-6.0V of that power coming in. In my FM/AM days, with a Savage.... WAY back when I owned a Savage, sometime in the early oughts, 2002 I think. I could not get a certain servo to work in my Savage that worked just fine in a NTC3. I was running two different radios and the servo would work just fine in the TC3, but would not work under braking load in the Savage. Turns out that the RX in the Savage (A Novak synthesized RX) took in up to nine volts DC, but only distributed 4.8V back to the servo. The servo was designed to run on 6.0V at that time, and did not work very well with only 4.8V. The JR radio in the TC3 only accepted a 5 cell hump pack, or a BEC from an ESC, and put out 6.0V to the servo.

I plugged everything in on the bench to test the output voltages coming from the RX's and found out that even though they will accept a certain amount of voltage, there are some that limit what goes out. Might be rated up to 9V in, but only 4.8V goes out.

Just something to think about.