It is currently Thu Dec 12, 2019 12:14 am

All times are UTC - 6 hours




Post new topic Reply to topic  [ 10 posts ] 
Author Message
 Post subject: High Power Servo Harness?
PostPosted: Thu Aug 08, 2013 9:27 pm 
Offline
User avatar

Joined: Tue Aug 23, 2011 8:09 pm
Posts: 275
Location: Round Rock, Tx
It has been a little over a year since our first "big" helicopter (Goblin 630). That was our first heli with a receiver battery rather than a BEC. We used a Hobbico Life battery plugged into the AR7200BX with just one servo connector. We never had any issues but eventually I added a Scorpion Back Up Guard just for my peace of mind. On our Goblin 700 with Pro Tek servos we use a 3S lipo with a Scott Gray Reactor HVX. Very cool but maybe overkill and certainly not cheap or light. For our New Raptor E700 I am using JR 8717s on the cyclic and a JR MP80G on the tail. We used these on our Ballistic 635 with the same setup as our Goblin 630 (Life pack with a back up guard) with no issues. But this setup really bothers me. All the current for the servos runs through two very small wires into the FBLs. I have seen a couple of variations of HV servo harnesses. I saw one today that separates the signal wire from each cyclic servo and puts them on a new connector with the + and - wires connecting directly to the receiver pack. Then the August/September issue of RC Heli Pilot had a nice article on a harness that just uses two servo extensions to connect two servos directly to the battery and runs two through the receiver (see the attached photo from the magazine). This seems to make sense and is easy and cheap. Then I saw an interesting pre-made harness sold by some of the Asian retailers. Here is a link to that one:

http://www.himodel.com/electric/4-way_H ... DPC-4.html

The downside is that it includes a BEC. The positive is that at that price I suspect that it is just a resistor like a tail servo step down. This seems like a great idea. However I am leery of trusting a $2000+ heli to an $8 harness. So I have a few questions:

What do most people do to connect a receiver pack to high power draw servos?

Is there a decent quality pre-made harness that can be purchased for this?

When soldering extra connectors to the receiver pack do you solder to the original wire or do you solder directly to the cells?


After more than year and several big helis we have not had any failures just using a single servo connector to power everything. Of course we may be having issues that are covered up by the backup guards. I know that we are flirting with disaster. This is one of those questions that I would not want to ask on one of the larger/more intense forums. I am guessing that to some degree it may be a question that evokes strong opinions, like asking "What is the best battery connector?" or What is the best flybarless controller?".


Attachments:
RCHP servo harness.jpg
RCHP servo harness.jpg [ 100.14 KiB | Viewed 4546 times ]

_________________
Rod R.
Top
 Profile  
 
 Post subject: High Power Servo Harness?
PostPosted: Thu Aug 08, 2013 10:03 pm 
Offline

Joined: Wed Jan 25, 2012 9:55 pm
Posts: 187
I run two receiver cables into the vbar and use brushless servos. That works fine for me.

But those 8717s are notorious for being power hungry. The reactor may be overkill. But if I were in your shoes I'd probably build some sort of harness so that the servo cables aren't pulling power straight off the FBL rail. Not because I think it is essential, but because I'd feel better about it. Though I'd probably run the idea by Alex or Justin first and do the vbar pitch pump test :)


Top
 Profile  
 
 Post subject: Re: High Power Servo Harness?
PostPosted: Thu Aug 08, 2013 11:18 pm 
Offline
User avatar

Joined: Tue Aug 23, 2011 8:09 pm
Posts: 275
Location: Round Rock, Tx
Thanks Phillip. I want to avoid the reactor for E700 just because I want to keep this one light and simple in keeping in spirit with the design of the helicopter. At this point I may just replicate the harness from the RCHP article because it is simple and easy. I don't know if its a good long term solution. I am surprised that there isn't much in the way of commercial solutions out there.

_________________
Rod R.


Top
 Profile  
 
 Post subject: Re: High Power Servo Harness?
PostPosted: Fri Aug 09, 2013 2:53 am 
Offline

Joined: Mon Aug 05, 2013 12:24 pm
Posts: 28
Hello,

HE10 connectors (servos) are rated for 3A continuous, a lot more peak (they can dissipate quite a lot of heat through wires).
The iKon/BRAIN servo connector board can handle 10A (double copper thickness).

If you can get power through 2 servo conectors, then you can handle 6A continuous and much more peak, that is more than enough for the hardest 3D flight on HV servos. From feedback I have, pilots put back at most 200mA on the RX pack for each at least 4min flight. That's an average of 3A over the entire flight (worst case). One servo connector is on the edge, but two is enough margin.

Thomas.


Top
 Profile  
 
 Post subject: Re: High Power Servo Harness?
PostPosted: Fri Aug 09, 2013 4:36 am 
Offline
User avatar

Joined: Thu May 02, 2013 11:48 am
Posts: 461
They way I approach powering high amperage servos is one of two ways:

#1: Run dual servo wires from the Rx battery into two servo ports on the FBL unit.

#2: Remove the power & ground wires pins from each servo lead, cut off the pin and solder all the servo positive wires together (not to a single point) with an additional two servo leads going to the FBL unit; then do the same for the grounds. Then connect the power & ground main wires to the Rx battery.

Option #1 has redundancy and simplicity going for it; but you are using the FBL unit as a power bus. Option #2 has simplicity and high current capacity; but, and this is a big but, you are making the main wire going to the Rx battery into a power bus and this needs to be done with care so to be stone reliable. In fact I would call it "a can of worms" both figuratively and literally. There is also RC power distribution units, but I question if these are any better than what is inside the FBL unit.

Personally, I went with option #1, I have dual servo leads going from an oversized LiFe Rx battery directly to the iKon FBL unit. Even though my Savox 1257tg/1290mg servos can pull a lot of amperage, the simplicity of using the FBL unit as the power bus brings reliability.

If you want to pay for the supplies, I'm willing to solder you a power bus with plug in connectors. But again I'm suggesting letting the FBL unit be the power bus.


Top
 Profile  
 
 Post subject: Re: High Power Servo Harness?
PostPosted: Fri Aug 09, 2013 6:31 am 
Offline
User avatar

Joined: Wed Jul 27, 2011 8:13 am
Posts: 1523
Location: Caldwell, TX
I just run two servo cables from the rx battery to the iKon. No problem on the Goblin 700 with 4 brushless Torq servos. Super easy. Our two electrical engineers may have different thoughts, but I'm with Thomas on this one.

_________________
Bobby Barr
DT Helis
Graupner USA


Top
 Profile  
 
 Post subject: Re: High Power Servo Harness?
PostPosted: Fri Aug 09, 2013 7:00 am 
Offline
User avatar

Joined: Fri Aug 26, 2011 4:04 pm
Posts: 280
Two wires into your FBL unit will be fine. If you do not have any empty connections on your FBL unit, use some y-harnesses.

I have a dream. That someday these engineers and designers will have a red and black wire soldered onto their buss lines and sticking out of the RX or FBL case that we can then attach our preferred connector to as Spektrum did with the AR7100 :)


Top
 Profile  
 
 Post subject: Re: High Power Servo Harness?
PostPosted: Fri Aug 09, 2013 7:06 am 
Offline

Joined: Tue Dec 18, 2012 1:31 pm
Posts: 268
I'm planning on using this for a large plank w/ ET Guardian (which can't handle servo power like the iKON):

http://www.servocity.com/html/servo_power_boards.html


Top
 Profile  
 
 Post subject: Re: High Power Servo Harness?
PostPosted: Sat Aug 10, 2013 12:46 pm 
Offline

Joined: Thu Aug 25, 2011 9:14 pm
Posts: 1910
Location: Bryan, TX
I used some 20awg short y-harnesses to get power into my iKON. The iKON on my 600N is the previous model that you couldn't put a power wire into one of the ports that was actually free. I have two power inputs, no problems.

http://www.hansenhobbies.com/products/c ... d_fj20-06/

_________________
A.K.A. ben_beyer


Top
 Profile  
 
 Post subject: Re: High Power Servo Harness?
PostPosted: Wed Aug 21, 2013 7:25 pm 
Offline

Joined: Tue Aug 20, 2013 3:18 pm
Posts: 9
Maybe_James wrote:
Two wires into your FBL unit will be fine. If you do not have any empty connections on your FBL unit, use some y-harnesses.

I have a dream. That someday these engineers and designers will have a red and black wire soldered onto their buss lines and sticking out of the RX or FBL case that we can then attach our preferred connector to as Spektrum did with the AR7100 :)



This would be the cat's ass!! :) Would be alot easier to get more current to the servo's and to the Receiver / FBl controller..

The "Y" adapter is a ok idea, only problem is it makes for messy wiring, longer wires..


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 

All times are UTC - 6 hours


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group