FAQ Setting up and programming multiple servos per surface; programming Hitec servos

[cwojcik]

nice write up Cody.

We have found that using a Fromeco Quad Current meter the easiest way to set up ganged servos.
Its fast, easy, no guessing.

http://www.fromeco.org/Products/05FRCQCM/View attachment 3252

Thanks Jim, that looks like a handy tool. Not too much money either!

 

[Notorious B.E.N.]

Nice write up! I still have the DOD videos from back in the day on my hard drive.

 

[djmoose]

What I mean is that if you set your end points as far as they will go, the servo will probably stop moving before you hit the end of the stick travel. So you will be limited by the travel of the servo, not the radio.

below: us = nanoseconds

From my research I've found this is not the case.

With my 8FG on a new model with end points at 100 connected to a BLS157 I get ~42degrees of throw.
With setting the end points to 140, I get close to 60 degrees each way. (58.8 actually...based on us calculations and the Futaba S-Link software)

For Futaba at least...I'm sure the Hitec servos have a different range...they're programmed for 120 degrees of movement from 920us to 2120us. (1520us being their center)

With my 8FG set at 140 end points, the radio only sends out a range of 937us - 2112us

(coinsidently, it's prudent to state that the end point adjustment number (on the 8FG) is in fact a percentage...but it's the percentage of the us on that side. 100% end point is 420us. 140% is 588...or 42 degrees and 58.8 degrees. Also, these calculations are based on the assumption that the BLS157 is programmed for 120 degrees of total travel with a total range of 1200us...you get that by taking 2120us-920us)

So, the 8FG cannot move a BLS157 it's full 60 degrees of motion (without programming the servo)

Another funny thing is that the 8FG centers all channels at ~1524us. That equals a .4 degree difference from what the S-Link software programs. That's not a lot AT ALL...it's about 5 clicks of subtrim to get it to 1520...but in relation...if you program hitec servos...they're programmed for 1500us...so if you hook up my 8FG...the servo center will automatically be off by ~2.4 degrees.

What's my conclusion? If you want the most torque and resolution out of your servos...you need something to measure pulse width off of the Rx so you can meaure what your Tx is actually sending...and then decrease your end points so any sub-trim won't effect your travel in that same direction. This requires some math, but I believe it might be possible that this can make the difference between needing 2 or 3 servos in a wing.

I still have some work to do. I'm going to measure my A9 tonight and record the numbers.

After playing with the S-Link software last night and I generally like it. I don't like that the neutral setting is only done in 1/4 degree increments. I also wish you could see the angle measurements. The protractor is so small...so the only angle measurements you can be sure of are the +60 and -60. More to come on that...because you should be able to do math to figure everything else out, but that's what I'm working on now.

I also like the idea of the new Futaba radios that allow you to do the s-bus programming directly. I wonder if that allows you to dial-in the centers and end points to exactly what the radio is sending out.

 

[ghoffman]

Nice article Cody! Last year, Cody came over and he helped me set up the wings of a new 104 AJS with programmed 7955's (only because I had a JR 9303). Over the Winter I will switch to 4, Futaba BLS-157HV's. I just got a new DX-18 and it has a 7 point servo balancing feature, so I will put them on their own channel and use that feature.

 

[ghoffman]

BTW, Cody and I wrote a "Gassers for Newbies" article, it is a Powerpoint/PDF file. She we post that as well?

 

[econpatric]

Wow! Questions I've had forever were answered with this! Thank you so much to Cwojick and djmoose! Also many thanks to you ghoffman for the gassers for newbies posting! That info is priceless! This forum is amazing!

 

[gyro]

Wow! Questions I've had forever were answered with this! Thank you so much to Cwojick and djmoose! Also many thanks to you ghoffman for the gassers for newbies posting! That info is priceless! This forum is amazing!

Thank you! Please tell your friends about us

-G

 

[econpatric]

I have, and I will continue to brag up this site! Please consider doing a section on radio programming for various radios. I think there are many newbies, like me, who would benefit from some expert info on programmable mixes and general settings on their 9503 or DX18's. I have often wished that the guy who does the 3DHS build videos for IPS motors would do a tutorial on his basic radio setting in regards to his maiden of the specific aircraft at the end of each build.

 

[gyro]

I have, and I will continue to brag up this site! Please consider doing a section on radio programming for various radios. I think there are many newbies, like me, who would benefit from some expert info on programmable mixes and general settings on their 9503 or DX18's. I have often wished that the guy who does the 3DHS build videos for IPS motors would do a tutorial on his basic radio setting in regards to his maiden of the specific aircraft at the end of each build.

The foundation has been laid: http://www.3drcforums.com/forumdisplay.php?133-Radio-Programming-Help

 

[Bivens]

Nice write up Cody!