Caution: Savox SB-2271SG Cyclic Servo Bench Test Results

[akamullen]

I will check my receivers for blinking/lockouts after every flight, I think it was Matt Nasca that pointed out that JC is running the same setup. JC has been flying the X7 for a long while now with no issues, Flying hard, so I doubt this set up will have issues, but I will keep an eye on it all the same.

[irishmatt18]

Now this is only an issue with the Savox servos and not the Torq ones correct?

[akschu]

I must say that many of the conclusions posted in this thread do not make sense to me. Here are some of the things I'm thinking when I look at this:

1. I seriously doubt there is anything in the servo that would cause it to slow down or pause unless the brushless controller inside could detect that it lost motor timing or there was an over amp condition. The first one could happen due to a brown out with load on the servo, but the second one shouldn't happen with a BEC failing and should be more likely with the battery.

2. The brownout on the BEC is only for a split second because the other servos keep working. This tells me that the brownout triggers something, but something else keeps the failed servo in the failed state.

3. The fact that it works on the beastx leads me to believe that the vbar has some sort of servo protection built in.

Anyway, I have these same servos and I also have an oscilloscope, so I'll be able to figure out exactly what is happening, however I don't have a v-bar only the beast X. I'll try to make time later tonight to mock this up, but I am in the middle of moving so this depends on if I can find my scope or not.

schu

[Chris Sexton]

Originally Posted by irishmatt18

Now this is only an issue with the Savox servos and not the Torq ones correct?

Yeah the Savox Servos pull an INSANE amount of power and it would seem the VBar bus can't handle it, but the Spektrum/BeastX bus can, if only barely.

I have already set mine up for RX pack, I am going to leave it that way. Better safe than sorry in my book.

[Rollin_3z]

Its not just vbar. I flew my Logo hard and it browned out as well. I lost control for a few seconds in a fast backwards inverted hurricane and saved it. I landed right away and sure enough the sats were blinking. My flying buddy JasonKachur was with me and saw it happen.

I run a Beastx with a Ice 100 lite using the internal Bec in the Logo. I am in the process of upgrading the power supply to fbl/servos in that system too. And I'm waiting for my mini vbar.

The simple fact is if you run FBL,high voltage servos, high head speed and fly hard..check to make sure you give A LOT of supply current to your setup

[akamullen]

Originally Posted by Rollin_3z

I run a Beastx with a Ice 100 lite using the internal Bec in the Logo. I am in the process of upgrading the power supply to fbl/servos in that system too.

If you are using the Ice internal bec, that would explain it, the ice controllers have a VERY low amp rating compared to a WR or CC BEC PRO, they have about 3 times or more amperage capacity.

I am not worried at all. I tested my set up with one person moving both sticks very fast while I was holding the swash so the servos could barely move it. I was putting a lot more pressure (almost stalling the servos) than any flight would do.

[irishmatt18]

I tired using the Ice 100 with the internal BEC on my X5 with stock servos and a Vbar and that DID NOT work at all, I couldn't even do slow pitch pumps...


I just want to make sure the CC BEC PRO V3 will work with the Vabr and Torq Servos.

[Rollin_3z]

I guess I learn the hard way, why the frigg put a bec into an esc when its not enough..geez

[akamullen]

Originally Posted by Rollin_3z

I guess I learn the hard way, why the frigg put a bec into an esc when its not enough..geez

I agree, They def. should up there bec amp capacity in the ice 75 and ice 100.

Matt, as far as the torque servos go, I don't think you will have a problem at all, they do not spike high amps like the savox do. you should be fine.

[Rob Cherry]

Originally Posted by akamullen

If you are using the Ice internal bec, that would explain it, the ice controllers have a VERY low amp rating compared to a WR or CC BEC PRO, they have about 3 times or more amperage capacity.

I am not worried at all. I tested my set up with one person moving the sticks very fast while I was holding the swash so the servos could barely move it. I was putting a lot more pressure (almost stalling the servos) than any flight would do.

Right, if you guys can't get brown outs on the bench doing ultra fast pitch pumps and loading up the blades, it won't happen in the air.

[MrMel]

Here is one of the test that RV (Vstabi team) did with Savox HV on 2s lipo
close to 30A for 3 servos.

[akschu]

This is why the new scorpion controller is worth the extra money. I trust it more, and I don't need another BEC, to bad it's not available.

Once I get my scope hooked up I'll be able to figure out the voltage dip and duration. That will allow us to sort out what size capacitor to use to fix this.

Another option is to get a small 1000mah 2 cell lipo and set the BEC to 8.0v then charge the battery to 4v per cell, then plug it in and use it as a buffer pack. That way it will always be able to pick up the slack, but it will last since it's not fully charged all of the time. This would work well: http://www.hobbypartz.com/98p-25c-1100-2s1p.html At 50c bust it should be able to put up the 30amps that the servos need for the few ms when the regulator is catching up.

schu

[Rob Cherry]

A DC-up should work, I'll probably try that out. That will have more than enough capacitor storage.

[akschu]

Looks like the voltage drop is only 5ms or so, but the battery takes 40ms to recover. What battery is this?

[irishmatt18]

Originally Posted by akamullen

IMatt, as far as the torque servos go, I don't think you will have a problem at all, they do not spike high amps like the savox do. you should be fine.

I hope so. It makes me nervous if that were to be the case...

[Rollin_3z]

Originally Posted by akschu

This is why the new scorpion controller is worth the extra money. I trust it more, and I don't need another BEC, to bad it's not available.

Once I get my scope hooked up I'll be able to figure out the voltage dip and duration. That will allow us to sort out what size capacitor to use to fix this.

Another option is to get a small 1000mah 2 cell lipo and set the BEC to 8.0v then charge the battery to 4v per cell, then plug it in and use it as a buffer pack. That way it will always be able to pick up the slack, but it will last since it's not fully charged all of the time. This would work well: http://www.hobbypartz.com/98p-25c-1100-2s1p.html At 50c bust it should be able to put up the 30amps that the servos need for the few ms when the regulator is catching up.

schu

Yes, I changed my setup this morning to bec set at 8.4v and put a fully charged 1800 2s lipo in parallel..moving the sticks fast and for a long time, the pack read 4.00v and not warm. I let the system sit for 3 minutes and the pack was fully charged again, but not over voltage! Only fly for 4 minutes..so it looks like I'm good to go.

[akschu]

That works, but I would setup the system at 8.0v because it's really hard on lipo batteries to be fully charged and these servos are plenty fast on 8v.

If you do that though, I would discharge the battery to 8v since plugging in more potential into a switching regulator can cause strangeness.

schu

[Rob Cherry]

Originally Posted by akschu

That works, but I would setup the system at 8.0v because it's really hard on lipo batteries to be fully charged and these servos are plenty fast on 8v.

If you do that though, I would discharge the battery to 8v since plugging in more potential into a switching regulator can cause strangeness.

schu

Makes sense, then you could just leave it mounted in the heli, and never charge it. A lipo at 4.0v /cell isn't that hard on the pack, it will last forever. Instead of leaving it at 4.2V.

I wish there was an easy way to wire it all up so you wouldn't have to do anything except plug in the main packs, lol. With this setup, you still have to plug in the main pack first, then the buffer pack. If you forget the lipo, you're not buffering. And, if you forget the correct order and plug in the lipo first, you could fry the BEC. lmao.

[akamullen]

Originally Posted by irishmatt18

I hope so. It makes me nervous if that were to be the case...

I run the outrage servos in my 700E, been flying that hard for 100+ flights with the bec pro on 6S, absolutly no problems.. many other guys run that set up as well. never heard of any problem until the brushless savox came along. your good to go Matt!

[irishmatt18]

Sweet.