RE: Power Expander or not -that's the question
 

You definately gotta use a golf tee somewhere :D:D:D

RE: Power Expander or not -that's the question
 

I think I could get by with a golf tee, but only becuz I've got a trick titanium & carbon fiber tail wheel assembly.
zx32tt[sm=biggrin.gif]

RE: Power Expander or not -that's the question
 

that calls for 2 golf tees :D:D:):D

RE: Power Expander or not -that's the question
 

Just out of curiosity I looked up the current draw for the hi tork hitec servo's,
HS-5990, 59980 4.2 amps @ 6v, 5.2 amps @ 7.4v

sort of makes light wiring and plugs look useless on multi servo control serfaces [:-]

RE: Power Expander or not -that's the question
 

I've not been able to get the 5955 to pull above 2.7 to 3 amps on a bench with severe loading (stalled) but if that's what the manufacturer wants to state, so be it.

RE: Power Expander or not -that's the question
 

We hooked up a H9 Amp/Voltage tester to a 5955TG in my plane and another larger plane too, It connects in series with the servo(Aileron). I then took readings with full deflection, holding & then full stall readings: At full stall the highest reading was around 1.11A, full deflection readings typically were 600MA or less,and only momentary, holding at center was almost zero reading(10MA resolution). We tried several different servos with about the same readings, then we looked at voltage drops under the various loads(2700mah 5 cell Nimh pack). The lowest voltage was around 6.2(fully charged pack=7.2 V no load). The meter is a digital read-out so it probably doesnt pick up very quick spikes, but gives an idea of what is "really" going on inside your receiver circuit. Its strange, some of Hitecs
people claim up to 4 amps fully stalled, others say only 2 amps fully stalled, and readings of 1-1.5 amps under a "normal" set-up. I'm only seeing 1.11amps under full stall??? I tend to believe none of my 30% planes servos ever draw 1.11 amps during flight(all 5955's).
I am still going with a P.E. Pro in my 33% Yak, I could go with 2 receivers & no P.E. but I like the safety features the P.E. has. It helped that I got the P.E., 3 Li-ion batts,3 switches & more for less than the price of a new receiver.

RE: Power Expander or not -that's the question
 

The Servo Power Board sold by Servo City was mentioned a few times in this post, so I contacted them today to get a few specifications from them. The wires supplied in the kit or assembled board, are 5" long. All of the wires are heavy duty. I am assuming that would mean 22g wire. I didn't ask specifically. The Power Expander will deliver 20 amps total. For $10.00 they will solder all of the wires to the board.

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

Greg

RE: Power Expander or not -that's the question
 

the only problem I see with that power board is it looks like 8 channel in and 1 outlet per channel, it doesnt specify one way or another.

RE: Power Expander or not -that's the question
 

Looks to me like its not much more than an extension of a receiver bus. Most of the 72mHz receiver busses would handle a lot more than 20 amps. I haven't kept up with trhe 2.l4 receivers so if they were de-rated to lower ampeages the consumer got screwed in favor of increasing component sales.

RE: Power Expander or not -that's the question
 

Here is what it have

Futaba 9 Channel PCM Receiver (came with my 9C Super)
2 2300mah 6V Nimh. 1 for the receiver 1 for the Ignition
4 - 7955TG for the ailerons and elevators
1 - 8611 for the Rudder

I also have the option of 2 1800mah 6V Nimh's as well.

With this setup i could plug a 2300 and a 1800 into the receiver and 2300 for the Ignition?

TOM i know you suggested a move to A123 batts but i've got these and would like to use them.

Geoff

RE: Power Expander or not -that's the question
 

Run what you have for sure. Just keep track of the battery condition. Nimh batteries don't have the ability to provide large and sudden demand amperage some other batteries do but they are by no means inadequate for the task. I'd use both of the 2,300s for the flight system and use the 1,800 on the ignition. You'll fly for hours on 1,800 mAh with most twin ignitions.

RE: Power Expander or not -that's the question
 

Right on, thanks very much

geoff

RE: Power Expander or not -that's the question
 

Cute, but does not provide nearly the same features:

Switching (PE can use a safe switch)
Battery redundancy (PE works as a batt share)
Bad battery isolation
Multiple servos on one channel

RE: Power Expander or not -that's the question
 

Full stall would be a deflection of the surface under flying conditions - wind presure on the surface requiring the servo to maintain it's postion despite the air pressure.

RE: Power Expander or not -that's the question
 

Yeah I don't see where the receiver and servo batteries are isolated. They say you won't burn up your rx with more than 6 volts but doesn't the battery soldered to that servo board end up connected to the receiver bus? ....which is connected to the receiver battery?

RE: Power Expander or not -that's the question
 

A "stalled" servo is one that is trying to move more "weight" that it was designed to move or hold. It is one that has been ovecome by the object it was trying to control. It may be that the servo is trying to drive a flight surface farther than the surface will permit due to improper linkage adjustment and geometry. The concept that a stalled servo is one at full deflection in flight is absolutely incorrect in every way.

In any case the servo has been asked to do more than it was designed to do, causing it to "stall" and draw excessive amounts of current. In a nutshell that's why people see high amp draws. They set the plane up poorly.

RE: Power Expander or not -that's the question
 

The Servo Power Board isn't a substitution for a PE, it is just another option.
If you buy two Servo Power Boards you can have multiple servo plug ins for every channel. If you look at the picture of the circuit board, you will see it is easy to jumper the servo plug ins for about any multiple servo set up you would ever need.

If you look at post #206 by mixmaster, you will see he had a hard time getting the 5955TG servos to take much more than 1.5 amp stalled. The 20 amp capacity of the Servo Board would be more than adequate for most any set up. Even at 2 amps per servo, the power board would be under it's capacity.

The power board is nothing more than a heavy duty buss. The Futaba 7 channel FASST receiver is rated at 8 amps constant, an 10 amp surge. The Spektrum receivers are rated higher, but I don't think the buss will be rated at 20 amps. The receiver can be powered separately, or directly from the Power Board. The Servo Board will get more power to the servos than the receiver alone, and that is mainly what I am looking for.

I really don't think a batt share is necessary. For over $100.00 difference between the Servo Power Board, and the cheapest PE, the power board offers a nice alternative.

Greg

RE: Power Expander or not -that's the question
 

It's a cryin' shame what they did to the 2.4 receiver busses. The 72 mHz stuff would easily handle 60 amps or more. They were only tested to 60 Amps (JR) because the manufacturer didn't think any more would ever be necessary.

RE: Power Expander or not -that's the question
 

O.K. Time for me to ask a question.....what is the main difference between a "Smart-Fly" regulator and a "PowerBox brand" system?? what do they really do other than make for a easy connection of two large voltage battries. And allow one to hook up the servo leads of lets say four servos to the same channel without "Y ing" them togeather. I have noticed that PowerBox brand systems are a lot more money than Smart-Fly systems. Does one do a much better job than another or are they two different systems for two different applacations???
Help me out here guys. need to know.

RE: Power Expander or not -that's the question
 

Here's a copy of an e-mail to SmartFly:

At 11:43 AM 12/31/2008, JoeAirPort wrote:


PS: What is the actual current rating of the Super Switch? Some guy on RCU is saying only 5 amps. This switch is perfect for a 50cc aerobat (Extreme Flight Yak and Extra in my case).


Reply from Smart Fly: Hi Joe,

The switch is good for 5 amps continuous. This is enough for a 40% plane when two

are used. Peak load would be in the 15-20 amp range. You should never have more

than an amp of continuous current on your size plane. A 40% should not have more

than 2 amps continuous current.

RE: Power Expander or not -that's the question
 

It gets better.

Don's Hobby Shop has recently with a quick release draft of "servo set up issues" that they are including with all of their latest shipped orders. It covers high amp draw, linkage geometry, and other set up issues that contribute to high amp usage and receiver re-boot/dropout, Essentially it states that many modelers are trying to treat the symptom rather than the problem by throwing money at the problem rather than reducing the current use by correctly installing their equipment. Using his 40% Carden with 13 8611 and 8711 servos as an example, the idle current in that plane is roughly 200 mAh.

My set ups with eight 8611 servos and one 4721 mirrors his experience. Setting up linkages using an amp meter rather than an ear makes a tremendous difference in amperage consumption.

RE: Power Expander or not -that's the question
 

one thing regarding setting up linkages that I have scratched my head over often it the number times I have seen ailerons set up with same size horns and multi servo's all set up on the same hole on each, and same on the servo. To me thats gotta be causing issues with uneven throws, causing either geartrain issues or hi amp draws at the least. I always try to get my linkage points the same distance from the hinge centreline even if it means modifying or redrilling horns. I never had a problem since I started doing that

RE: Power Expander or not -that's the question
 

You note something that is frequently done wrong. You are dead on correct in setting up equidistant from the hinge center line.

Any other waqy will cause binding throughout the range of motion. It may work at either end of the servo travel but it will be a hard fight in the middle. Setting up multiple servos at offset distances from a hinge center line kills servos, regulators, switches, and batteries.

In my installations is normal for ganged servos to draw about 10 milliamps at idle with a quick high draw to get them moving. At full deflections those same servos will be back to 10 or 20 milliamps. I use a meter to set up most every installtion, even single servo installations. It tells me all I need to know about how well the linkage geometry functions. This is a primary reason in not having a need for an expander. My stuff never hits those high amp draws experienced by some others, and therefore remains well within the design tolerance of wiring and other components.

RE: Power Expander or not -that's the question
 

These threads always seam to lose sight of the original question. That was do I need a power expander in my 35% plane?

I had a 30% plane with 4- 8411s, 1-8611 and throttle servo. Powered by 2- 2100 lions into 2 miracle switches with built in regs.
No Power Expander. This plane had close to 1000 flights with no issues. I 3D the heck out of this plane it was finally shot down.

I also have a 35% QB 260 with 4-5945s ail, 2-5955s elev, 2-5955s rudder later changed to 1 8711, 1 throttle servo. Powered by 2- 2100 lions into 2 miracle switches with built in regs. No Power Expander. This plane has over 600 flights with no issues.

Both these planes are awesome flying 3d. I personnel dont think I could feel a difference If I had stronger servos and power system.
That being said you bring up having to have the latest greatest. I believe if I replaced all servos with the latest greatest power hungry JR servos my power system would have been inadequate.

I also have a QQ phython with 4-5955s ail, 2-5955s elev, 1 8711 rudder, 1 throttle servo. Powered by 2- 2100 A123s Smartfly Power Expander Pro no regs. I used the PE because of simpler wiring and 1 failsafe switch. The PE cost me under $100.00 and I saved close to that by not using switches and regs.

Here are examples of planes with and without PE s. I have no problems with either setup. I do like the A123s because I dont need regs. I have more than enough amperage. I can fly all day and when I charge it takes only 15 min

I dont like spending more than necessary because I believe the best plane is one you can afford to crash. I dont want to be to nervous to come down on the deck because of not being able to afford the hobby.

Here is a pic of my Phython

RE: Power Expander or not -that's the question
 

Ok, in reply I dont think we left the topic to begin with, the bottom line is that if everything else is set up correctly and the servo's are working freely you dont need a power expander, All my larger planes have had single rx, 2 or 3 matchboxes as needed, with a battery to each, and I have had no issues at all. While I can see possible advantages with a power expander I dont see it as a must have.