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

[irishmatt18]

Heck Matt I would get that just for the cool lights...

[rcbirk21]

awesome heads up on the dc-up. but be aware it is only good to 8.4v, not 9v for those running a higher voltage

[irishmatt18]

I thought HV servos only went up to 8.4v anyways...

[rcbirk21]

Originally Posted by irishmatt18

I thought HV servos only went up to 8.4v anyways...

thats what they are rated for, but i run my hitec 7955tg's in my planes at 9v. I mean there is no issue, its just that they are rated for 8.4v because that is a fully charged lipo. some servos are coming out with 9.0v ratings as well. another great option with the cc bec pro

[akschu]

Looks like that fromco box will work just fine, but keep in mind that the capacity of the capacitors is only one factor, the other is the internal resistance. The caps I spec'd out have extremely low internal resistance so they will react very fast.

Another option would be to install the CC cap pack, but I just couldn't bring my self to spend $20-$35 on capacitors, not that I'm cheap, I just can't see spending that on something that I can build for $10 in 20 minutes.

schu

[Matt Nasca]

Here's the DC-UP on my X7 when I was testing it.

https://www.helifreak.com/showpost.p...4&postcount=53

[Chris Sexton]

Well no RX pack will fix my newest problem. The elevator servo has almost a 1/2 of an inch of gear slop. And when i power up the servo it isn't any better.

Pulled it off. Sending it in ad soon as I figure out who I can send it too. But I am worried. I have heard complaints about savox warranty.

Probably going to just order a set of
The outrage after all.

Oh Dave


Sent from my iPhone using Tapatalk

[vr360]

Originally Posted by cdsexton

Well no RX pack will fix my newest problem. The elevator servo had almost a 1/2 of gear slope. And when i power up the servo it isn't any better.

Pulled it off. Sending it in ad soon as I figure out who I can send it too. But I am worried. I have heard complaints about savox warranty.

Probably going to just order a set of
The outrage after all.

Oh Dave


Sent from my iPhone using Tapatalk

Do it. You will NOT regret it. After 100ish flights on my Outrage 9180/9188's they have zero slop. Run those MF'ers @ 8.4v with the BEC pro and you are good to go.

[Rob Cherry]

Oh great. lol. I fly mine so damn hard, now I'm worried about my 2271's.

For me, the MKS won't be fast enough, I need the 0.06 speed, so I may try the HV Futaba S9352HV.

Speed: 0.06 sec/60°
Torque: 305.6oz/in

[Chris Sexton]

Yeah your flight style is insane compared to mine Although I have seen plenty of smack 3D done with those outrage servos.

.10 is as fast as any of the other servos I have, and my synergy's JR8917HV at 8.4 are only doing .11 and they still out fly me

[Rob Cherry]

LOL, thanks!



Also, I'm not all that thrilled with the Savox "buzzing and beeps". They are loud m'fers! Just sitting on the bench powered up, with ZERO input, they will beep and chatter once every 30 seconds. So weird!!

[perfectregulators]

Originally Posted by Matt Nasca

This is another solution for those that want to add capacitors. This solution is already made and plugs right in, it's called DC-UP Mark 2. I've tried this myself (with JR8917s) and it really makes a difference in keeping the voltage up. The caps are 1.2 farad, which is huge!



http://www.fromeco.org/products/05frcdcupm2/

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).

[rcbirk21]

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 would for sure like one, as right now i am planning on running the dc up

[vr360]

nvm

[akschu]

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).

That's a good idea. I didn't put a diode in with my bec pro so I hope I didn't hurt it, I may open it up and look and see what castle did inside there.

Another thing we should put in place is a bleed off resistor. That will bleed off the caps when the system is shutdown.

schu

[Matt Nasca]

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).

Thank you for the information. How would a buffer pack work then with a BEC? Wouldn't it be the same thing?

[perfectregulators]

rcbirk21:
for same measure, make sure to unplug the dcup before unplugging the main flight pack, just in case it lets the smoke out of the bec.

akschu:
here is a 20a 100v rectifier that should work, there are higher current ones available too... http://www.newark.com/micro-commerci...ack/dp/51T4908

im not sure about the resistor for bleeding power because in order for it to bleed off voltage when the bec is powered off, it would have to bleed on the output side and if thats the case, then it will be constantly be bleeding while the bec is powered on, then defeating its intended purpose, unless a simple mosfet is introduced into the design that as soon as it seen 0v from the bec output, it would then open the gate which can be connected to the bleed off resistor which can then drain the stored voltage in the cap bank, but the voltage stored should only be appx 5 seconds, give or take 1-2 seconds, so the bleed off setup would only seem to take up valuable real estate on the pcb

matt:
a buffer pack would be run parallel to the output of the bec and can still back feed voltage into the bec when its powered off from the main flight pack. i can incorporate a buffer pack input which would be past the reverse voltage protection on the cap bank. only thing that brings up, would be having to disconnect that buffer pack after each flight as well so its not always plugged in. according to akschu's pics and o-scope data on these servos, a buffer pack doesnt seem necessary, just a good cap bank to provide the added power to the servos.

[akschu]

Originally Posted by perfectregulators

rcbirk21:
for same measure, make sure to unplug the dcup before unplugging the main flight pack, just in case it lets the smoke out of the bec.

akschu:
here is a 20a 100v rectifier that should work, there are higher current ones available too... http://www.newark.com/micro-commerci...ack/dp/51T4908

im not sure about the resistor for bleeding power because in order for it to bleed off voltage when the bec is powered off, it would have to bleed on the output side and if thats the case, then it will be constantly be bleeding while the bec is powered on, then defeating its intended purpose, unless a simple mosfet is introduced into the design that as soon as it seen 0v from the bec output, it would then open the gate which can be connected to the bleed off resistor which can then drain the stored voltage in the cap bank, but the voltage stored should only be appx 5 seconds, give or take 1-2 seconds, so the bleed off setup would only seem to take up valuable real estate on the pcb

matt:
a buffer pack would be run parallel to the output of the bec and can still back feed voltage into the bec when its powered off from the main flight pack. i can incorporate a buffer pack input which would be past the reverse voltage protection on the cap bank. only thing that brings up, would be having to disconnect that buffer pack after each flight as well so its not always plugged in. according to akschu's pics and o-scope data on these servos, a buffer pack doesnt seem necessary, just a good cap bank to provide the added power to the servos.

In thinking about this more, we don't need a resistor to bleed the caps because they will self bleed over time, as well as the RX/servos bleeding them off. As far as the back feed protection goes, I don't think that is an issue because a typical switching regulator uses a fet to switch on and off the inductor, and that fet is usually open when the bec isn't powered. The resistance of the output of the CC BEC pro is 1.5K, which at 8.4v is only .005 amps and that will drop with voltage which will bleed very quickly with the RX pulling on it.

I'm going to look around for pictures of the CC bec pro without a case since mine would be hard to dig out of the heli and see if I can figure out how they did the regulator, that would confirm that this isn't a problem.

schu

[fusionsx00]

Would a diode placed on the rc pack stop the bec from from getting voltage back to the pack but allow voltage to travel to the servos when its needed?

I use diodes in my solar panels to stop any voltage going into the panels after dark.
Once the sun comes up they start feeding the power like usual. But never seen voltage going back to the panels

[akschu]

Yes, a diode would work, but keep in mind that it's got to flow 30 amps at 8.4 volts which is a bit. Diodes also have forward voltage drop so with that amount of current, it's going to generate some heat.

I'm going to call castle in the morning and see what they say about buffer packs or cap packs. There are probably a lot of people using the spektrum RX cap, or the many anti glitch packs on cars with the bec pro, so I'm sure they have some feedback from the field. I suspect it's fine.

If castle says there aren't any known issues then I'm going to put 4 caps on mine and fly.

schu