MKS DS92A+ & Brown-Outs

[scallybert]

Has anyone seen these servos (apparently) causing power brown-outs ? If so, please post the details of your configuration; and what symptoms you saw.

[mattie-lodge]

Hi, The DS92A is quite power hungry servo for its size. (I have a set in my Proto 450)

If you run them off a normal ESC BEC (for instance Align) and apply pressure to the head when operating them you can cause the BEC to drop below voltage.

To get over this problem I use a Castle 10 AMP BEC to power it separately which has worked fine for many flights now. I wrote about it on our team website when they were fitted in my 450 pro, it might help

MKS DS92A's in my Trex 450 PRO

[heathy]

MKS DS92A+ & Brown-Outs

I'm using them with a 95i on tail on my warp. Using a kontronik koby 55 with its own bec and no problems yet. I've done the bench test while plugged into the skookum software while watching the live data on voltage. At best I could get a .4 v drop but not enough to stress the futaba rx.

Also from what I've read on HF this problem is more of a spektrum one. Something to do with the amount of power required for the sats.

Like Mattie plenty of guys using external becs

[scallybert]

Hi, The DS92A is quite power hungry servo for its size. (I have a set in my Proto 450)

If you run them off a normal ESC BEC (for instance Align) and apply pressure to the head when operating them you can cause the BEC to drop below voltage.

To get over this problem I use a Castle 10 AMP BEC to power it separately which has worked fine for many flights now. I wrote about it on our team website when they were fitted in my 450 pro, it might help

MKS DS92A's in my Trex 450 PRO

Yes, I think I'd read that.

I've got DS95s in a couple of T-Rex 450 Pros, and decided to replace the DS410Ms in another Pro.

Teh 95s have been great. I happily set up the 92 heli (rigorous method... ); then was messing about with it and noticed that enthusiastic wiggling of the collective stick gave a funny response. More susteained enthusiasm, and the SK-720 showed errors.

Popped the servo/swash links off - still problems.

This was with DSMX sats. Rebound with Tx set to DSM2 (ie in brown-out detection mode....). OMG! The initial power-up was enough to make the RXs blink. If I managed to get the lights solid, it was really easy to make them blink with cyclic input. Then you could make it misbehave & upset the Skookum too.

Now, this was with a CC 10A BEC powering it all (I use this for set-up). Switched packs; switched to ICE 50 BEC; all as bad.

Plugged in 3 DS545s (no links, as the DS92A+s were), no problem.

In a fit of paranoia, I repeated the collective wiggle test on a 450 Pro with 3 * DS95s; power off an ICE 50 Lite BEC (also switched to DSM2). This was fine - vigorous wiggling couldn't provoke the problem, (Phew !).

Now, either these DS92A+s are badly behaved in some way; or there's something strange on this heli. (Maybe something upset with the SK somehow. Not obvious how, though.)

[scallybert]

I'm using them with a 95i on tail on my warp. Using a kontronik koby 55 with its own bec and no problems yet. I've done the bench test while plugged into the skookum software while watching the live data on voltage. At best I could get a .4 v drop but not enough to stress the futaba rx.

Also from what I've read on HF this problem is more of a spektrum one. Something to do with the amount of power required for the sats.

Like Mattie plenty of guys using external becs

Interesting. I am using Spektrum.

I was running a 10A external BEC and seeing the problem. This kind of suggests it's not that the power supply isn't up to it.

However, I have wondered if I'm seeing something like spikes from the 92s on the +V upset the RXs, and this is what upsets the SK (rather than the SK losing power).

Do you have any links for the Spektrum problem on HF ?

I guess I'm wondering if the DS92A+s are just a bit brutal in some way. [I expected the DS95s would be more heavyweight than the 92s, and the 95s seem well behaved.]

[heathy]

Here you go

Brown out with Koby 40 ESC on the bench - HeliFreak

[scallybert]

One thing to add.

With an SK plugged into a laptop, it's *possible* that the SK & sats are being powered via USB; whereas the servos are powered from the BEC.

ie, you might not see RX/SK brown-outs even if the BEC, etc are struggling.

Also NB, I was seeing the problems with no swash/servo links. ie unloaded DS92A+s

[heathy]

MKS DS92A+ & Brown-Outs

Hmm. That's a good point. I will do it again with a multi meter rigged up and no sk GUI.

[scallybert]

Some further thoughts..:

*** I'm already using CC 10A on the bench, when seeing the problem. Hence powering from one of these doesn't help. The next step up (eg to CC BEC pro) seems totally OTT & heavy. ***

One possibility is to just avoid DS92A+s. Before this issue, I was totally happy with my DS95 configuration (except for weight & expense...) . I don't want to tempt fate, but these have been great, AFAICS. [Superb heli, even in my ham-fists...]

However, I'm now paranoid that the DS95 configuration might be marginal, and just waiting to fail. I was considering swapping the tail DS520/S9257s for a DS95i (for weight saving), and this might tip things further towards/over the edge, as the DS95i is likely to be more hungry than the DS520 [or maybe just burstier, and more likely to trip an over-current sensor...]

So here's what I'm now thinking..:

I have ICE 50s on some helis. I could swap these for ICE 50 Lites, plus a 7g Gryphon BEC; split the power, so the external BEC powers the swash servos; while the ESC BEC powers the FBL, RXs & tail servo. Even if the swash servos trip the ext BEC (which is probably unlikely), this won't make the FBL or ESC reset. This seems like a good configuration with no weight penalty - but some wiring complexity; though a tidy harness might be quite cool.

On DS95 helis that already have an ICE 50 Lite, I could combine the same mod with a switch to DS95i on the tail to keep weight down.

I think I can now see a way forward that addresses my paranoia, whilst not compromising performance.

[BTW, don't think I'm a cutting edge pilot. However, good servos make FBL helis fly better; and weight just loads things up and reduces flight time. I'm a bit obsessed with weight, as each upgrade (some of which aren't voluntary - eg new Align motors) seem to make things heavier.]

[cjcj1949]

Sounds like some servos think they are ics. Perhaps they need to be decoupled. They might need a capacitor or two across their power rail. Might need something like a 47 microfard and 0.1 microfard disc in parallel. Needs to be close to the servo, especially the disc. I can now measure the spikes as I have a scope, if you want to send one over. As a bodge you could try using a servo extension lead and connecting the capacitor/s across it. (5v-0v).

[scallybert]

Sounds like some servos think they are ics. Perhaps they need to be decoupled. They might need a capacitor or two across their power rail. Might need something like a 47 microfard and 0.1 microfard disc in parallel. Needs to be close to the servo, especially the disc. I can now measure the spikes as I have a scope, if you want to send one over. As a bodge you could try using a servo extension lead and connecting the capacitor/s across it. (5v-0v).

I tried one of the Spektrum 4700uF capacitors (SPM1600); and it may have helped, but didn't cure things.

I'm going to play with the dual BEC set-up.

[scallybert]

[...]So here's what I'm now thinking..:

I have ICE 50s on some helis. I could swap these for ICE 50 Lites, plus a 7g Gryphon BEC; split the power, so the external BEC powers the swash servos; while the ESC BEC powers the FBL, RXs & tail servo. Even if the swash servos trip the ext BEC (which is probably unlikely), this won't make the FBL or ESC reset. This seems like a good configuration with no weight penalty - but some wiring complexity; though a tidy harness might be quite cool.[...]

Just tried this (on the bench), and it seems to work great.

Sats (in DSM2 mode {for brown-out detection}) stay solid - as you'd expect, since SK is powered from ESC BEC.

Interestingly, the white LED on the Gryphon BEC flickers a bit when the swash is worked. Maybe the DS92A+s are brutal. However, I'm confident this is a solid set-up. And lighter than the previous configuration.

Cool 8) .

[heathy]

MKS DS92A+ & Brown-Outs

Interested in a picture of this set up. How on earth have you split power with the sk without power bus?

[scallybert]

Interested in a picture of this set up. How on earth have you split power with the sk without power bus?

I hacked & spliced 3 servo extension leads, so they take power from the other BEC, not from the SK pins.

In the picture, the 3 connectors to the SK are at the top right (ground + 3 signal).

2 servo connections at the bottom; 3rd in front of the BEC leads.

[heathy]

MKS DS92A+ & Brown-Outs

I see. Nice work. If I ever detect any problems with the koby's bec then i will go this route.