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Old 04-12-2012, 06:14 AM   #1
lucasy
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Default Servo Matching - Servo Programming VS Smartfly/powerbox

Hi Guys,

maybe opening a can of worms here.. but..
i am setting up my 100cc airframe. I have HS7950TH's and the programmer.
I have a Smart Fly power expander in the airframe currently..
I also have JR Match boxes floating about, as well as a Power Box RRS, so i have a few options when it comes to setting up multiple servos on a single control surface.
now the question is.. what are the pros/cons with just setting up the matching by programming the servos, VS using a Matchbox or Power box device???

Cheers

Lucas
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Old 04-12-2012, 07:07 AM   #2
Ohio AV8TOR
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I am no expert on this having never used a Smartfly/powerbox but one thing I will add is with the Smartfly every servo gets it's own power supply instead of distribution from a small bus in the receiver. With a 100cc you are right on the edge maybe where this might help. Are your ailerons single or dual servos each?
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Old 04-12-2012, 07:33 AM   #3
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What radio and reciever are you using? is it possible to run all servo's on their own channel?
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Old 04-12-2012, 08:44 AM   #4
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I'm not an expert on the subject either but I have spent a lot of time on the subject. I also have a thread on the IMAC web-site Servo Centering) that may be of interest to you.
I'm sure you will see a lot of different opions on this but here's mine.
First, Unless you have the "servo arms" set at EXACTLY 90% from the center line of the servo with NO subtrim, you will you will not only experience considerable difficulty in matching servos and in fact, depending on some other factors that may exsist, you may not be able to match them. You may come close (and for some that's good enough) but they will not likely be perfect.
To my knowledge, there are only two ways to achieve a perfect 90% setting mentioned above WITHOUT using sub trim.
First is to use a programable servo like the one you discribed and program the center position. The second is to use the method I developed using AirWild Uni Hub servo arms. I should mention here that I have no connection with AirWild and the method I developed if free to anyone that would like to see it on the IMAC web-site.
Someone could write a book on all of the things that are envolved in matching servos but it's probably best to address them one by one as the questions appear.
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Old 04-12-2012, 09:39 AM   #5
Carruthers43
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Steve is a bright man and his idea is awesome and I have seen it in person and it is simple and by far the BEST!
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Old 04-12-2012, 09:47 AM   #6
vmceachern
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Being a K.I.S.S. systems advocate I still say you can't beat the simplicity of a smartfly or power box. Especially for your average joe. I prefer the smartfly myself. 2 cents
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Old 04-12-2012, 09:54 AM   #7
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Just another take on this. I finished last week changing the radio gear in my 35% Carden from JR to Futaba. I'm using the 8FG Super that has preprogrammed mixes one of which is 4 aileron/2 flap/2 elevator selection. I've never has such ease in setting up a plane before this. Using a pair of inline amp meters, starting out with zero subtrim and neutral trims and selecting SWB arms so they would be 90* to the hingeline. The left wing went so quick with only a couple steps of endpoint adjustments to get nearly zero amp draw at full deflection and at rest. The other wing needed just a few subtrim adjustments to get 90* on the arms and the same few endpoint adjustments for a clean setup. No matchboxes, no extra special mixing, no nothing. Careful selection of gear and placement with proper linkage geometry is the way to go. K.I.S.S. to the Nth degree...

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Old 04-24-2012, 12:00 PM   #8
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If you really like KISS go with a power safe receiver and programmable servos (Hitec)
The Power safe servos from JR/Spektrum can take upto 12 servos. Program the servos using the programmer for zero amp draw at centre and end points and you are done. You can link the channels together on the transmitter and you can use trims etc. On my 7 channel DX7 and 8 channel DX8 i just a simple 20awg custom built Y lead to your specs from Radical RC for the dual servo alierons and they have worked great for more than 2 years now. You will near a lot of expert opinons to the contrary but keep it simple and safe... no regrets.
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Old 04-24-2012, 03:15 PM   #9
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You have paid for servo programming by purchasing the 7950s. There is no need for a powerbox or smartfly. Get a AR9100/9110 powersafe RX and program the servos using the HT programmer. Plug your 4 Ail leads into 4 different ports on the powersafe RX. You lose nothing as far as delivering power(u probably actually gain by removing regulation done by PB/SM) to the servos and you remove additional potential failure points that a PB or smartfly would introduce.

In my opinion, there is no better setup than this. Super Simple, low weight and ultra reliable.

Now for the negatives with your setup....

There have been people that have seen pots on 7950 start to fail causing jitter. Search 7950 jitter on FG. There is a good debug video. Secondly with the setup recommended above, to not use high voltage batteries... 7950s and Powersafe RXs don't work will together at high voltage if the leads are long. There is info on that here on FG also. These two problems are probably a bigger issue than how you choose to power the plane.
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Old 04-25-2012, 09:57 AM   #10
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Quote: Originally Posted by hbutler
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In my opinion, there is no better setup than this. Super Simple, low weight and ultra reliable.
Bingo!
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Old 05-21-2012, 04:09 PM   #11
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I just picked up a 100cc edge and he pulled the rx but has the power expander pro still in. It has 2 servos per aileron, 1 for each elevator, 2 going to a bellcrank/push-pull for the rudder, and one for throttle. I got an 11x and he was using a 9303 but I would think it would be ready to go since he had one channel for each wing, one for elevator, and one for rudder but I'll check to make sure. The servos could be already programmed to work togehter on the ailerons, elevator, rudder. They are JR digitals so is it possible to program them like the hitecs?

I can use the servo match in the 11x and that would use all 9 channels on the RX though but I would like to add smoke eventually. I could just pair up the rudder servos to one channel for example to get an extra channel for smoke. My main question is subtrim okay to use to get the arms at 90 using the servo match in the 11x?

Any suggestions welcomed on what to do. It has the opto kill and I was planning on using Life packs to power the power expander. Then order a fail safe switch like the flag switch for it. He had batteries going to (2) different switches then a regulator then the smartfly. Then just keep the setup for ignition power; battery, switch, and then regulator.

Last edited by hugocraft; 05-21-2012 at 04:16 PM.
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Old 05-21-2012, 06:59 PM   #12
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Quote: Originally Posted by Flybye Steve
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First is to use a programable servo like the one you discribed and program the center position. The second is to use the method I developed using AirWild Uni Hub servo arms. I should mention here that I have no connection with AirWild and the method I developed if free to anyone that would like to see it on the IMAC web-site.
Someone could write a book on all of the things that are envolved in matching servos but it's probably best to address them one by one as the questions appear.
Whats the difference in setting the center position with a programer and setting it with subtrim?
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Old 05-21-2012, 08:37 PM   #13
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With a Smart-fly EQ-10, it controls the servos so that if you had a servo failure, it is much easier to replace it. It also gives each servo full power and battery redundancy.
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Old 05-21-2012, 08:53 PM   #14
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Quote: Originally Posted by ghoffman
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With a Smart-fly EQ-10, it controls the servos so that if you had a servo failure, it is much easier to replace it. It also gives each servo full power and battery redundancy.

only if you short out the signal wire. If the power and ground wires were to short together, you would have no protection.
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Old 06-06-2012, 10:59 AM   #15
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Quote:
I also have a thread on the IMAC web-site Servo Centering) that may be of interest to you.
Is there a link to this thread or method?

Sounds intriguing...
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