Ultraguard as a 'buffer'

[mattscupoftea]

I'm a little confused. . .

This all relates to my Logo 500/550sx.

I'm currently in the process of replacing my Savox 1259/1257 servos for some lovely Futaba 251/451s (Thanks Maj!) for the lower current draw characteristics of the Futabas. This has been brought on because I have gone with a Turnigy K-Force 100LV which I installed whilst my Kontronik 100LV was off for repair (the replacement Jive is still sat in an unopened box holding its value for the moment)
The Turnigy's inbuilt BEC struggles just slightly with the high current draw of the Savox and browns out the Vbar here and there on the bench during cyclic/pitch pumps/stick wiggling (something that happened with the original ESC in the combo deal that got me into Logos in the first place - the Hacker X70).

So basically, out of curiosity, before changing out the servos, I thought I would try the Opti Guard out (even if only to experience the fabled high-power LEDs!).
The setup is K-Force 100LV, Savox servos on a Logo 500, OptiGuard sharing a Y-lead with the inbuilt BEC into Vbar.

With the OptiGuard, no matter how much stick-wiggling I do on the bench (Motor backed up from the main gear, blades off and TH on!) I can no longer make the mini Vbar brown out. So it seems that the OptiGuard is doing the same job as the buffer pack previously did, although the LED does not light, so the suggestion would be that it hasn't 'kicked in' with power.

My question comes more from curiosity than anything, though ultimately for safety I guess (I like to know hows and whys with this sort of equipment as far as my little brain is able to cope with the information!) - Is the OptiGuard supplying power the whole time even when not in rescue mode (no bright white LED) or is it something else?

My guess would be (seeing as the LED doesn't come on to suggest Opti 'on') that perhaps there is a capacitor onboard the Opti somewhere which is 'stepping in' at those potential brownout moments with just enough juice to compensate for the teeny current 'blip'??

Can anyone throw some light on this?

Matt

[mattscupoftea]

ps sorry for using so many words for such a simple question. . .

[trillian]

My understanding is that it will kick in for short transient amp peaks that draw down the voltage just for a very brief time but when it activates for those really short durations the LED doesn't come on yet. Otherwise you could have the LED coming on all the time even though it's all really OK, not truly in 'rescue mode'.

[Mark_T]

Is the OptiGuard supplying power the whole time even when not in rescue mode (no bright white LED) or is it something else?

As Trilian says, the UG430 will support the voltage during brief transient voltage drops without alarming, but if the voltage goes too low and stays too low then it will alarm.

This is a useful ability, but I would not intentionally use the UG430 this way, if the BEC can't handle the load you need to deal with the root cause of the problem.

Changing the servos as you are doing is one way to approach this, but do test again without the UG430 in place to make sure the BEC is now coping OK.

[mattscupoftea]

For sure that's the plan. Good to know that what is going on is to be expected.
To be honest mark, if I still get the brownouts, I may well just put the jive back on it with the opti backup and not risk anything. .. I've got a feeling that it will be fine now though...

[acidla]

It's been reported that no brownouts occur using the ultra guard.

[Mark_T]

It's been reported that no brownouts occur using the ultra guard.

The UG430 should still be used as a back-up though, not as a crutch for a weak BEC.

If a quick stir of the sticks on the ground causes a brownout then you should address that problem as the OP is doing, not just patch it with the UG430.

[mahbouni]

I tried on UG430 on a 500 sized heli not long ago. I have some Futaba BLS servos powered by a YGE 100LV BEC. I never had any brown outs but I decided to try an UG430 as a backup solution. Initialially I charged the UG430 up to only 90% to test if it really does charge off the BEC. After 4 flights the little lipo was down to only 72% so it definitely didn't charge it. I did notice the cyclics seem more responsive with the UG430 so I believe it was functioning as a buffer to the YGE. Nothing wrong with that. However, this lead me to do some more testing. I left the UG430 powered up from the BEC on the bench for about an hour and it still didn't charge it. Only when I got the lipo down to 70% and re-initialized the UG430 did it enter charging mode. The UG430 (my one anyway) does not continuously switch between charge and discharge mode during flight. It decides once when you power it up. Another thing is it charges upto only 92%. This is a good thing because you don't want to fully charge a LiPo in cold weather.

So my conclusion was that the UG430 functions very well as a back up system. It can be used as a buffer but the intelligent charging becomes redundant. If you need a buffer for a 6V BEC then you might as well use a 4s NiMh as it always automatically charges off your BEC. You don't need electronics to do that with a NiMh. The problem with a 4s NiMh is you need to plug it in and remember to disconnect it every flight. Some people solder in a switch. The other problem is if you're running HV servos then a 4s NiMh is only about 6V when fully charged. Even if you go up to a 5s NiMh then you're only at 7.5V. So for HV servos @ 8V+ you would need a 2s LiPo or equivalent. Personally I wouldn't want to connect a LiPo directly to my BEC without some intelligent charging. This is where I think the UG430 becomes useful again. I use a Kosmik 200 so I have no need to buffer the BEC but an UG430 is an ideal backup solution.

[mattscupoftea]

Just to reaffirm what I thought I had said in the first instance, I have replaced the Savox servos with Futaba 451/215s for the exact reason that I didn't want to be running a system which involved 'making up for' issues such as the brownouts.
I didn't buy the OptiGuard as a buffer in any way - rather, I noticed on testing it that it seemed to act as a buffer, and this was what prompted my question. Sheryl (Trillian) has pretty much understood and answered my question with this. . .My understanding is that it will kick in for short transient amp peaks that draw down the voltage just for a very brief time but when it activates for those really short durations the LED doesn't come on yet. Otherwise you could have the LED coming on all the time even though it's all really OK, not truly in 'rescue mode'.

Since installing the Futabas, I can't get the Vbar to brownout on the Turnigy BEC even if I add a little load to the servos by holding blade grips etc, for quite a bit of stick wiggling (30sec ish).

When I put the OptiGuard on the system too, I notice that the little red LED shimmers on now and again during cyclic wiggles, which suggests to me that it is still providing some sort of current to the system even though there is no risk of brownout. . . I guess this makes sense and explains partly how yours was dropping in charge, Nick, in use.

[Mark_T]

When I put the OptiGuard on the system too, I notice that the little red LED shimmers on now and again during cyclic wiggles, which suggests to me that it is still providing some sort of current to the system even though there is no risk of brownout. . . I guess this makes sense and explains partly how yours was dropping in charge, Nick, in use.

It would tend to indicate that the voltage is still dropping by more than 0.5V for very brief periods.

That is not all that unusual and is relatively easy to get most power sources to do that momentarily. At least with the UG430 in use, it stops the voltage drop as it hits 0.5V.