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


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Chris Sexton
03-27-2012, 12:00 PM
The frame survived, not one crack. One servo toasted, everything else was a right off

:bawl:OK

Rollin_3z
03-27-2012, 08:23 PM
:bawl:OK

Ok, I just spent 1075.00 for another servo, 2 batts, blades and kit parts...lets see if I can get more than 3 test flights out of this rekit...:peace

Can you imagine if this was a Outrage Goblin?

Rob Cherry
03-27-2012, 08:28 PM
Man, sorry dude!

Another confirmation that vBar (with satellites), BEC and Savox 2271 DO NOT PLAY NICE.

vr360
03-27-2012, 08:47 PM
It's the servos. :face

Luckily I have the Torqs!

Rob Cherry
03-28-2012, 12:07 AM
It's the servos. :face

Luckily I have the Torqs!

Because they are so friggen fast! I'll take 'em! Ninja tocs!

:bacon

Actually, it's vbar, not the damn servos. We need BEC's to step up their game AND/OR vbar needs to increase the buffer on their 3.3V rail, both mini and fullsize failed and browned out!

To me, this is just more obvious evidence that all BEC's have a limitation, they will never replace the consistency or reliability of an RX pack. The are stepping the voltage at a certain frequency (hz), and now these new servos have surpassed the stepping frequency rate and draw more power, faster than the BEC can deliver. Beastx may have a larger 3.3V rail buffer, but that doesn't fix the BEC, only hides its problem.

:D

Rollin_3z
03-28-2012, 12:28 AM
Man, sorry dude!

Another confirmation that vBar (with satellites), BEC and Savox 2271 DO NOT PLAY NICE.

Yeah you're right man...I just added a LiFe 6.6 pack and my sbec set at 6.0 volts. Plus a capacitor for good measure!

http://i1093.photobucket.com/albums/i434/rollin_3z/IMAG0344.jpg

Rob Cherry
03-28-2012, 12:54 AM
Yeah you're right man...I just added a LiFe 6.6 pack and my sbec set at 6.0 volts. Plus a capacitor for good measure!

Looks like its ready to fly! (almost)

:bacon

joe1l
03-28-2012, 02:16 AM
Hey guys,

When i first got into this hobby i was using Hitec A9 because i wanted the telemetry feature. I noticed that i was having complete power shutdowns using same servos, bec etc others were using on the same helicopter...i couldnt understand what was going on. I ended buying a Futaba 8FG because i was starting to have suspicions that my Hitec electronics were behind the failures. One thing i knew was that the Hitec required voltage to be above 3.5v where Spectrum and Futaba could go as low as 2.7
I decided to do some bench testing at the time using 3 INOLAB 760MG servos. I did not mount the servos or anything i simply moved the sticks on the bench. I discovered that because of the telemetry the same exact servos using the same exact power source at same voltage would draw 30% to 50% more current when plugged in to an Optima9 RX vs my R6008HS RX. The difference between the two grew even greater as load increased.

I noticed that someone was using a DX8 and just wanted to point this out as Telemetry could be part of the reason why some people are having issues while others are not.

here is the link that pointed out the issue (http://www.helifreak.com/showthread.php?t=267041) that luckily made me switch to Futaba!

akamullen
03-28-2012, 03:38 AM
I'm not running Telemetry, but I am running DX8 spektrum, no problems here. I think this is a Vbar issue, not spektrum. My beastX with spektrum receiver is working fine with these servos. no lockouts or brownouts. I believe JC is running the same setup beastX, Spektrum, Bec Pro, on one of his with no problems.

MrMel
03-28-2012, 03:43 AM
I'm not running Telemetry, but I am running DX8 spektrum, no problems here. I think this is a Vbar issue, not spektrum.

It's rather that bigger Spektrum receivers have bigger built in capacitors so they can hide the problem longer, but sooner or later they run out too.
Measure voltage drop on the processor and you can see you playing with fire.

VBar and others has smaller so its seen there faster.

akamullen
03-28-2012, 04:27 AM
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
03-28-2012, 12:02 PM
Now this is only an issue with the Savox servos and not the Torq ones correct?

akschu
03-28-2012, 12:30 PM
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
03-28-2012, 12:30 PM
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
03-28-2012, 12:57 PM
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. :banana

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


http://i1093.photobucket.com/albums/i434/rollin_3z/IMAG0345.jpg

akamullen
03-28-2012, 01:03 PM
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
03-28-2012, 01:03 PM
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
03-28-2012, 01:07 PM
I guess I learn the hard way, why the frigg put a bec into an esc when its not enough..geez

akamullen
03-28-2012, 01:10 PM
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
03-28-2012, 01:50 PM
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.

:thumbup:

MrMel
03-28-2012, 02:34 PM
Here is one of the test that RV (Vstabi team) did with Savox HV on 2s lipo
close to 30A for 3 servos.

akschu
03-28-2012, 03:03 PM
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
03-28-2012, 03:10 PM
A DC-up should work, I'll probably try that out. That will have more than enough capacitor storage.

akschu
03-28-2012, 03:10 PM
Looks like the voltage drop is only 5ms or so, but the battery takes 40ms to recover. What battery is this?

irishmatt18
03-28-2012, 04:37 PM
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...