Can a 30A ESC with 2A BEC support 4 or even 6 HXT900 servos?

[snuffy]

After some kind guys on here talked me down from a 2200KV motor for my first plane (FT Swappable Trainer with 4 servos), I now have a NTM Prop Drive 28-26 1200KV in my sights for it. I'm part way through the build, and also have a Versa Wing cut out!

I would like to use a Turnigy 30A Plush 2A BEC, I think?, unless there's a better, more cost-effective option? Being a complete noob, I am only 60% certain I've made a good choice.

I would like to know if the above Turnigy Plush would support the 4 servos? I read somewhere that I might need a 3A integrated BEC, or a separate BEC module? Any suggestions?

I would also like to use it on a future build (Bixler 2, with flaps, hence 6 servos). Would a 2A integrated BEC be able to support this or am I being overly optimistic? Would I be right in thinking that I would need to purchase again for that build?

Battery: probably one of these: 2200mAh, 3s, 20C

As ever, your guidance is greatly appreciated.

Cheers,
Snuffy.

 

[Craftydan]

Snuffy,

What a linear UBEC in an ESC can support usually depends on the voltage of the battery. What battery do you plan to use for this?

 

[snuffy]

Snuffy,

What a linear UBEC in an ESC can support usually depends on the voltage of the battery. What battery do you plan to use for this?

Thanks Craftydan, sorry, I wasn't aware of that.

I was thinking of buying a one of these batteries: 2200mAh, 3s, 20C

I have updated the original post with the battery.

Thanks for your help!

Snuffy

 

[Craftydan]

You'll have to look under the international warehouse listing, but the manual is in the files section (last tab in the section with the comments and reviews). there's one included in the package with it.

For 3S it's spec'ed to support 4 servos, 4S it's spec'ed to 3. this is an issue with cooling an linear UBEC's. They regulate voltage via "resistance" -- converting the power to heat. An external BEC or picking a ESC with a switching UBEC will help with this, but keep in mind either of those options will add weight. Likely small enough weight gain for a bixler2 to shrug off, but keep it in mind.

As for how to wire it up? If you choose to use an external BEC, pick which servos go where, and for the ones you choose to drive off the BEC, pull the signal wire out of the servo lead, insulate the signal wire's connector socket with shrink tube, and connect to the receiver. The power and ground wires then need to be connected to the power/ground in the BEC.

 

[NewZee]

Snuff... I use the NTM 26 28 1200kv motor with a 1300mAh 3s 30 C battery, and a 25A Turnigy superpush ESC and have never had a problem, I think you'll be fine with a 4 servo plane (I fly my power pod in several different planes)!

 

[snuffy]

Craftydan, thank you sir. I hadn't noticed that tab, excellent. So I see where you got the 4 micro-servos from and Hobbyking state that a micro-servo is in the range 5-10g, so mine fall within that range.

I have saved your second point about the wiring and put it with my build instructions for my next build; I'm sure that will come in very useful. I feel I may end up getting hooked on the RC hobby.

Thanks again.
Snuffy.

 

[snuffy]

Snuff... I use the NTM 26 28 1200kv motor with a 1300mAh 3s 30 C battery, and a 25A Turnigy superpush ESC and have never had a problem, I think you'll be fine with a 4 servo plane (I fly my power pod in several different planes)!

Excellent. Thanks NewZee, that's comforting to know. I'm going to go with the 30A just to give me a little room for using it with future builds also.

Cheers,
Snuffy.

 

[pgerts]

4 servos or 6 servos - if small servos is no problem for 2A support.
4 large servos will need much more power.

 

[snuffy]

4 servos or 6 servos - if small servos is no problem for 2A support.
4 large servos will need much more power.

Ahh, ok. Would you consider 9g servos small? or is that the really micro-servos you're referring to?

I would be using 9g servos for ailerons (x2), rudder (x1), elevator (x1) and flaps (x2) on something like a Bixler 2

Just a thought... can you use a Watt-meter/Voltage analyzer or something to test the capability of the ESC to power the servos in a similar way to how you would bench test the prop/motor/ESC/battery on a new build?

Thanks pgerts.

 

[pgerts]

No problems to use an amp-meter.
I would check on the red wire from the ESC to the receiver. You need to put some force on all surfaces to get load on the servos.
If you can find an amp-meter with good resolution you can check with just one servo on the read wire and multiply the result with the amount of servos.

 

[snuffy]

Thanks pgerts, I understand, I will do that. Thank you all.

 

[xuzme720]

The other thing to consider is the type of plane you are flying. With a 3D plane, you are probably going to be using most of the servos, all at the same time and possibly to full throws while doing that. On a Bix, you are not going to be using all 6 servos anywhere near as much as you are using the 4 on a 3D type of plane. Later, if you are doing some real aerobatic stuff with a Bix or anything else, you might run the risk of overheating or brownout so just be aware. A realtime amp check will always be your safety blanket to make sure you aren't walking the edge...

 

[SteveRoby]

The other thing to consider is..
some servos are more fussy about minimum voltage , HXT900 not as bad as others Ive tested.
Some servos will do some strange things if the BEC voltage gets low...hence RCModel Reviews AXN build recommended a 3A bec minimum.

so consider either a esc with a 3A bec, or an external 3A BEC .
2A should be OK with 4 HXT900's, but personally I would never have less than a 3A BEC in a 4 servo plane.

These are reliable esc's, Ive used them in a few planes
http://hobbyking.com/hobbyking/store/__6460__Hobbyking_SS_Series_25_30A_ESC.html

 

[xuzme720]

Bruce does push his stuff much harder than your average beginner though. No harm in that as long as you plan for it and get it on video!

 

[snuffy]

Thanks SteveRoby and xuzme720, that's good stuff, appreciated. I did read that servos are under most stress when pullying G's, or constantly moving, like when I'll be over-controlling those sticks for the first time! I've watched Bruce's videos twice already. I like the look of those AXN type models.

I'm going to order the blue Hobbyking 30A ESC; it also has the 3A BEC. I'm going for that one as it's programmable for just a few bucks more. The Hobbyking seem to be the only ones with 3A BEC for the price; the Turnigy 30A Plush (comparable price) are only 2A.

I will definitely video the first flight and first crash (same video probably)

Thanks all.
Snuffy.

 

[xuzme720]

Of course it's better to error on the side of caution, but sometimes the budget won't allow it and you have to use what you have and be a little careful. It's nice to know you will have the extra wiggle room if you need it!
Good luck and let us know how it goes!