Futaba Sbus ?

[N-O-V8-R]

Oh my!....Decoders, Hubs, Terminal Boxes...etc. ....Oh my!. Do you realize how much money you have just spent!?!?!?!?
and none of the wire can handle any current. How do they expect you to pass 15A or more thru a 22-20ga wire????
Don't get me wrong, Futaba is an innovator in this sport, and a great/reliable radio, but because they rarely make anything backwards compatible, is the real reason I switched. Just couldn't afford to go that way.
Just push that "Tempt" button and get it over with. Go ahead and say it.. I wish to make my life simpler.

 

[N-O-V8-R]

Regarding your MKS HV777 Servos

• Electric Current Draw: 6.2A max. (8.2V) / 5.8A max. (7.4V) / 4.7A max. (6.0V)

Even at the Mid 7.4 Voltage range you have the possibility to pull upwards of 6A per servo.


Another Option if you stick with Futaba:

With all the money you would have to spend on "Decoders, Hubs, Terminal Boxes, etc." (or Dual Rx's)
Don't you think you would be better off with a "Smart-Fly" System.
This would allow you to regulate a lower 5V-6V to your Rx only, and still have
a REAL HV Power-Bus system to handle those (8) thirsty servos you bought.

With a Futaba Rx alone, you still have to feed your Rx with a battery using a standard JR type plug (3A rating).
Dual-Redundant means you could use two. Kind of a problem considering you have to feed eight servos.
I realize that the current listed is "Stalled", and the actual current is typically much less.
Another consideration is the Voltage drop using the smaller small wire to feed the Rx.
Remember, all the current for the "Whole" plane has to come from those two tiny battery leads.

Re: Decoders, Hubs, Terminal Boxes, etc.
Think of all the connections that can fail. (where they typically do)
and you don't even like to double-up an extension.
Did I mention NO Servo-lead Safety Clips on any of those connections....Oh my!!!
I guess there is always Heat-Shrink Tubing.

 

[DeathHorse]

Futaba receivers are fine on HV setups. No reg needed.

You can run battery power into any red/black +- wire anywhere you want or Y it in at the receiver if you run out of open slots. It's all the same bus.

Just run 4 or more connectors into the receiver (or Y them in with a servo at the receiver if you run out of open channels). If you Y them in you don't need the signal wire. You just need two or more connectors coming off each battery or switch going into the receiver. You could do three a switch if you wanted..

If we were actually pulling 6 amps a servo for any real length of time that alone would melt individual servo leads and L-ions wouldn't have enough power to snap a plane twice in a row. Four connectors gives you 12 amps continuous which would completely flatten a 4600mah A123 in 22 minutes...I don't think most people are close to that average draw with a 100cc plane...

HV actually makes it easier for the connectors and wires to support the same amount of torque/speed/watts compared to 6v systems.

It's too bad Futaba doesn't supply larger leads soldered directly to the main bus, because it would be so simple. You can accomplish the same thing by running more connectors into the receiver, but I couldn't say how many is equivalent. I'd ignore Sbus unless you had their servos.

 

[tylerzx9r]

Keep it coming..... learning a lot, and getting answers Thanks!

 

[N-O-V8-R]

For your reference, the approx. load carrying capacity of wire based on a 12VDC system, is as follows:
22ga. = 5A
20ga. = 8A
18ga. = 10A
16ga. = 20A
14ga. = 40A
12ga. = 60A
10ga. = 100A
8ga. = 150A
6ga. = 190A

So to answer Darkhorses question on an equivalence, it would take (8) strands of 22ga. to equal (1) 14ga wire, or (5) strands of 20ga..

What you need to ask Futaba the next time you talk to them, is the current rating of their "Bus", and if their Rx's are internally regulated to provide the electronics portion only 4.5-5V. If so, is this the weak link in the system, and why they stick with the 6.6V recommendation.

 

[DeathHorse]

I've seen posts by one of their reps or team pilots stating they've (the rep) tested the 6v receivers on 10v and they work perfectly fine. So running lipo into them would be the last thing I'd be worried about. If the internal reg was undersized and incapable of dissipating the heat from dropping the voltage we'd have dozens of former owners of HV large planes screaming it from the rooftops

The main issue specific to Futaba is the connectors being the source of power rather than wires directly soldered to the Bus. The Bus handles 40amps and it would take about 13 connectors run into the receiver to be equivalent to direct soldering. This is a moot point for anyone who just runs a few connectors into the receiver from the batteries because no 35% plane is flattening 4600mah packs in 22 minutes (12 amp average draw) or flattening 4600mah packs in 7 minutes (40 amp continuous) so there is is overhead with four connectors...average current is what is likely to melt connectors and heat things up and if people calculate their average current during flight I don't think they'll find it amounts to much based on the battery sizes people report using.

I don't know why Futaba doesn't offer receivers with high gauge power leads or at least give us nice solder points to add them, but they do work on HV just fine. I should crack one open and see if there's a place to solder to...

Obviously it makes sense to run larger gauge wire right up the receiver from each battery/switch then solder on a few 6 inch leads with connectors on them in parallel into the receiver. It certainly isn't a bad idea to run more than four connectors in on a 35%...

It will be interesting to see what happens in the future with the connectors and wire sizes in general if servos keep getting more power hungry. The lightest approach would probably be keeping the same connectors and 22g wire and just running 3 or 4 cells with slightly heavier receivers with bigger internal regs.

 

[N-O-V8-R]

Yes the larger input wire would be nice, especially in the case where a "Y" would be needed.
Instead of making a single connection, you have to make three.

 

[tylerzx9r]

Good points made by all! Thanks, Leaning more towards ordering a 6014

 

[Jlc]

Good points made by all! Thanks, Leaning more towards ordering a 6014

I would go with two 7008's unless you already have a 6014. Many benefits to running dual rx's.

 

[vegasking]

I've been running 2 - R7008's for two years now in 4-5 planes from 60cc to 120cc and not had a single problem. I use 2-3 J Plug battery leads into each receiver through a pigtail I've made coming from a HD Deans plug that's coming from a Wolverine switch.