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

[perfectregulators]

akschu:
this is direct from castles website...

NOTE: CC BEC Pro should never be operated in series or parallel with another BEC or backup receiver pack connected to the RX/Servo side of the circuit.

and while its true the fet controlls the voltage out through the inductor, there are several other paths going to the actual switch ic (dc/dc buck converter) and those can be the issue. we say not to use a buffer pack or cap bank for this reason as well on our hv bec + as it can cause that buck converter to go out

the amount of current is also a factor on the reverse voltage going back into the bec too.

hence the reason for a seperate device with the reverse voltage protection.

[akschu]

I looked at the DCUP and talked to the guys at fromeco. They said their stuff works fine with the castle bec pro, and that the only regulators that are hurt are the ones that can't charge the caps fast enough and end up burning up the inductor. He said that you will know if the bec can't handle caps because it will burn it up on startup. Shutdown isn't a problem because the FET is open and the RX bleeds off the caps really quickly.

Anyway, I ordered a DCUP to look at it, and because Kurt at fromeco was really helpful.

I'll post more when my caps come in, but at this point I don't plan on adding a diode.

schu

[Rob Cherry]

I got my capacitors in the mail yesterday, so I'll be trying out the BEC with capacitors this weekend. I have the Gryphon 75V BEC and the CC Pro V3, I'm not sure which I'll try first, probably the gryphon because it looks so much cooler!

Both will be running on 6S input, 8.4v output.

[akschu]

Rob,

I talked to Kurt@fromeco this morning and he said that they have been using the DCUP on many BECs over the years, and the only ones that burn up are the align becs, and that the problem is that the inrush current to charge the caps kills them.

Based on this information and what I know about switching regulators, I don't think that the cap potential at power down is an issue, rather, the caps stress the BEC when it's switched on.

I'll be getting my caps today, but don't know if I have time to play with this tonight, but you might want to hold off until I do a little testing to make sure they aren't hurting the bec on power on.

Once you are comfortable testing, I am really curious as to if this fixes the problem with the vbar/savox/cc bec pro combo. I suspect it will.

Once I'm moved into my new place and have my lab setup I'll be able to test much faster, and now that summer is close I'll be able to do some flight testing. Right now it's snowing so it might be a few weeks.

schu

[Rob Cherry]

Originally Posted by akschu

Rob,

I talked to Kurt@fromeco this morning and he said that they have been using the DCUP on many BECs over the years, and the only ones that burn up are the align becs, and that the problem is that the inrush current to charge the caps kills them.

Based on this information and what I know about switching regulators, I don't think that the cap potential at power down is an issue, rather, the caps stress the BEC when it's switched on.

I'll be getting my caps today, but don't know if I have time to play with this tonight, but you might want to hold off until I do a little testing to make sure they aren't hurting the bec on power on.

Once you are comfortable testing, I am really curious as to if this fixes the problem with the vbar/savox/cc bec pro combo. I suspect it will.

Once I'm moved into my new place and have my lab setup I'll be able to test much faster, and now that summer is close I'll be able to do some flight testing. Right now it's snowing so it might be a few weeks.

schu

IT WORKED!!!!!!!!!!!!!!!!



I hooked up 2 of the capacitors you spec'd out and it ROCKS. The servos actually seem to respond even faster now! I'll hook up 4 like you recommended, just for a good buffer size.

No more brownouts!

EVERYONE should do this, regardless of what BEC you're running, this will take a major load off of it.

thanks again schu!!

[CraneGrus]

Thanks for all the info guys.

I have a TDR with savox 2271/2 setup and WR Hercules Super BEC running at 8.4v.

I can confirm both the brownouts with heavy pitch-testing, and two successful flights and tests with DC-UP today.
No smoke either.

(The brownouts were shown in my vbar-log as 3.3v rail low voltage warnings -sometimes, and as 5 RC input ... errors -always )

[Rob Cherry]

Mine too! Flew 4 flights with no RX pack this afternoon. No brownouts, caps work perfect.

[akschu]

Looking at the 4 caps on the scope, I feel they are adequate, however, I wouldn't run 2, it really needs 4. As far as the bec ringing on startup, I don't see any sign of that. Voltages do fluctuate a bit, but I think it's because I was measuring at the caps, and they are plugged into the rx via a standard servo connector. I'm going tomove the caps to the bec wires next to the bec. I feel they will work better there.

Schu.

[Rob Cherry]

Yep, using 4. I have about 10 flights with them in and so far so good!

[Rob Cherry]

Originally Posted by akschu

Rob,

I talked to Kurt@fromeco this morning and he said that they have been using the DCUP on many BECs over the years, and the only ones that burn up are the align becs, and that the problem is that the inrush current to charge the caps kills them.

Based on this information and what I know about switching regulators, I don't think that the cap potential at power down is an issue, rather, the caps stress the BEC when it's switched on.

I'll be getting my caps today, but don't know if I have time to play with this tonight, but you might want to hold off until I do a little testing to make sure they aren't hurting the bec on power on.

Once you are comfortable testing, I am really curious as to if this fixes the problem with the vbar/savox/cc bec pro combo. I suspect it will.

Once I'm moved into my new place and have my lab setup I'll be able to test much faster, and now that summer is close I'll be able to do some flight testing. Right now it's snowing so it might be a few weeks.

schu

Have you tested the cc bec pro v3? So far so good on my end.

[Chris Sexton]

Originally Posted by akschu

Looking at the 4 caps on the scope, I feel they are adequate, however, I wouldn't run 2, it really needs 4. As far as the bec ringing on startup, I don't see any sign of that. Voltages do fluctuate a bit, but I think it's because I was measuring at the caps, and they are plugged into the rx via a standard servo connector. I'm going tomove the caps to the bec wires next to the bec. I feel they will work better there.

Schu.

Since I suck at soldering, would you consider making me a set of those for mine and I will cover parts and labor? I know I swapped over to outrage servos but I am thinking I will something to cover my bases.


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[akschu]

I don't mind at all, but wouldn't it be easier to ask a club member for help soldering? Also, soldering isn't hard, I'm sure you can do it, you just need decent tools. I can barely solder with a $10 pencil iron, but my 12yo son does ok with my solder station.

Another option is to buy a dcup. That would work just fine.

Schu

[Chris Sexton]

Yeah if I could find a dcup in stock.


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[akschu]

I ordered mine directly from fromeco. They have them in stock. I wanted to see what caps they use and test against my own solution (and they were really helpful on the phone, so I wanted to give them some business.)

Anyway, if you want me to build you something then pm me and I'll put something together.

Rob, are you using a vbar?

One last thing, these servos are crazy fast with the caps!!!

[rcbirk21]

i just ordered a DC up from rc aircraft components, and it has already shipped so i am assuming they are in stock

[Chris Sexton]

Just ordered one from Fromeco directly. Going to use this in conjunction with the SBEC in my new Scorpion 130A. Should be good to go with my new Outrage Servos. But I will bench test

[Rob Cherry]

Originally Posted by akschu

I ordered mine directly from fromeco. They have them in stock. I wanted to see what caps they use and test against my own solution (and they were really helpful on the phone, so I wanted to give them some business.)

Anyway, if you want me to build you something then pm me and I'll put something together.

Rob, are you using a vbar?

One last thing, these servos are crazy fast with the caps!!!

Yes, vbar. Vbar seemed to be the culprit, but yah the servos are even faster with the caps!! I soldered them up and mounted them inside the the area under the main shaft.

[Flying Dutchy]

Hi,

Ordering these in Holland is quite expensive so I was wondering if these would work?

http://www.ebay.nl/itm/Panasonic-100...item3f140ad959

This is the 25V version and internal resistance is 0,018 ohms, the 16V is 0,03 ohms....


Thanks!

Maurice

Originally Posted by akschu

I ordered mine directly from fromeco. They have them in stock. I wanted to see what caps they use and test against my own solution (and they were really helpful on the phone, so I wanted to give them some business.)

Anyway, if you want me to build you something then pm me and I'll put something together.

Rob, are you using a vbar?

One last thing, these servos are crazy fast with the caps!!!

[akschu]

Should be fine, but use the 16v version. The lower internal resistance is good since they will react faster.

schu

[joe1l]

Originally Posted by perfectregulators

1 issue that you can run into while running a cap bank is that most hv bec's are not current/reverse voltage protected, so if the bec has no power going into it from the flight pack and after you unplug it, the cap bank is charged and feeds voltage back into the bec and this can cause damage to the bec making it non-operational in order to make bec's small enough to want to use them, prohibits the use of creating a design that incorporates a good enough reverse current/voltage protection in place. what would be needed is a simple device similar to the dcup, but with a built in reverse protection circuit that is capable of handeling the current (10v/30A would be sufficient).

if there is a demand for a product like this that is small and can be used with any bec, we can produce one (already on the discussion table to develop one).

I think i might have been partially to blame for that discussion

I have 2 DC-UP's and have been using them for a while. I would not suggest using them with any BEC except the Jive's which allow the use of a buffer pack. You can and will more than likely eventually kill your BEC using one....I know this first hand. They can take up 30 + seconds to discharge once power is pulled...longer if you dont manually move the sticks to drain them.