Assan GA250 MEMS Gyro

[Jomaba4308]

I set the the gyro to 1520us/333Hz. I found the info for the servo Spartan website. As for getting into programming mode, the manual that came in the box was unclear but a few minutes ago I found the manual on the HK listing for the gyro which cleared things up for getting into the programming mode. Will try your servo test and check back here tomorrow.

[polarisflyer]

Great! Good luck!

[exblade]

Yo Jomba, check out the 119 page thread over on RC Groups regarding this gyro. the link is in the original post of this thread.

The above advise is correct, the rudder servo limits for AVCS (Head Hold mode) are set in the gyro, not your transmitter. The transmitter endpoints control the piro rate in HH.

There is a great setup video on the RC thread, here is the link:

http://www.youtube.com/v/KRbpVmcvo7M?fs=1

I like this gyro alot, but am not a 3D flyer.

Terry

[Jomaba4308]

Last night I went to try the servo test but somehow my receiver lost its bind and I didn't have a Y harness to rebind. I bought an ESC w/o a bec so I had to buy a separate bec which uses the bind port which is why I needed the Y harness. This mourning I was looking through the instructions for the receiver (just for the hell of it) and noticed in the pics for binding process I noticed that a bind plug was plugged into the bind port and a receiver pack was plugged into the auxillary port, I tried that and it worked after which I tried the test on the tail servo and saw no problems. Tonight I will try programming the gyro (hopefully with positive results).

[Jomaba4308]

I was able to get the servo endpoints programmed and now the servo moves the way like. My new concern is that the gyro doesn't seem to operate very fast, I have to rotate the heli several times for it to move the servo from one endpoint to the other. Is this normal for a MEMS gyro? Rotating the heli 90 deg does move the servo noticably but not much.

[5pound]

try more gain!

[polarisflyer]

Originally Posted by Jomaba4308

I My new concern is that the gyro doesn't seem to operate very fast, I have to rotate the heli several times for it to move the servo from one endpoint to the other.

Jomaba, is it possible that your gyro is running in rate mode? Is your LED solid or flashing Blue? Mine is ultra fast and very sensitive! Just tapping it lightly with my finger, causes the servo to make slight movement changes.

[Jomaba4308]

Originally Posted by polarisflyer

Jomaba, is it possible that your gyro is running in rate mode? Is your LED solid or flashing Blue? Mine is ultra fast and very sensitive! Just tapping it lightly with my finger, causes the servo to make slight movement changes.

When I have it running in rate mode the gyro seems to be more sensitive than AVCS mode. When in avcs mode the led is solid blue and rate mode led is off. What do you have for gain values?

[Jomaba4308]

Originally Posted by 5pound

try more gain!

I never would have thought about that. Right now I have it set at 60 in AVCS 45 in rate.

[Jomaba4308]

I just bumped the gain up to 70 and now the gyro moves the servo more. Haven't had a chance to do a flight test yet, still got some more work on setting up the main head.

[5pound]

Just be careful to much gain and it will wag! I would start at 60 to be safe! bench testing and flying are different. just et it at 60 and fly it. If it doesn't increase it until it wags then back off a bit!

[Jomaba4308]

I will try starting at 65 as that value did move the servo quite a bit more than 60 which barely moved the servo at all in bench testing.

[Jomaba4308]

The maiden flight of the heli & the gyro is going to have to be put off, one of the servos I bought for cyclic is defective.

[Jomaba4308]

Maiden flight of my Mini Titan with the GA250 gyro will be coming in another week.

[DGeorge]

I threw one of these GA250's in my 450 Sport and got it out for it's maiden today just before sunset. I only had enough time to get it off the ground and see that there is a ton of tail wag. Sensativity was set to 72 on my DX7 and i have my ball 7.25mm from the horn on my tail servo. Shold I move the ball in closer, or try turning the gain down a little? (I understand moving the ball is effectively changing your gain, though mechanical instead of electronically).

Originally Posted by Jomaba4308

Maiden flight of my Mini Titan with the GA250 gyro will be coming in another week.

I'll be interested in hearing how it goes.

[exblade]

DGeorge,

Try dropping your gain. Try around 66 or 68 and work up.

What tail servo are you using? Depending, watch the voltage and the frequency setting. Too high a frequency will fry your servo. Also, be sure to feel the tail servo after every flight to be sure it is not too hot. Vibrations can overwork it.

Enjoy,

Terry

[DGeorge]

Thanks for the info, I noticed after running through a battery doing some short (30 second) test spool-ups into a low hover that the servo was slightly warm. How warm would be cause for concern? It's a Henge 922 and I have it set to 250Hz (seems to be a nice servo, especially for $10). It would wag about 6 inches really fast back and forth. I have a DX7 so the gain settings need to be converted to use on a 0-100 scale. Are you suggesting those settings for actual gain at the gyro, or is that the DX7 converted values for the "GYRO SENS" settings?

I moved the ball to 5mm from the center of the horn, tightened my belt slightly and was able to eliminate all but a very small amount of tail slop. Hopfully all that's left is getting the gain set correctly.

Thanks again.

[exblade]

DGeorge,

The Henge at 250 Hz should be fine. On the gain number, I was talking about the transmitter setting. Pretty hard to ever figure the true gain. My number is for the DX6i as that is what I was using to fly my King with the GA250 on it. If you set up your DX7 NOT in gyro sense, but as a gear channel, then the DX7 acts just like the DX6i and you can use the gear switch to switch between head hold and rate. Since I fly both, this is quite handy. The Gyro sense menu was the one thing I despised about the DX7 until I stopped using it. It is quite handy to put the gyro in rate mode while you are moving the helicopter around or chances are pretty good that you will fry your tail servo when it sits at the end point. In theory, it should just sit there, but in reality they burn out.

Anyway, the GA250 transmitter gain setting is about the same as a Quark, just under 70.

I have quite a few GY48V's and 401B's and the gain settings of the GA250 run a little under those, but not much.

If you are getting heat on your tail servo, check your mounting and look for vibrations. As a safety measure, I have been putting some soft foam inside the case of the GA250 to prevent any movement of the board inside the case. This may not be necessary, but can't hurt.

BTW, once you eliminate the wag, if you have any bounce back, you can reduce the piro rate by reducing the rudder endpoints in your transmitter to around 75%. This has no effect on the travel limit of the servo as that is set in the gyro setup only.

Hope it works out for you.

Terry

[DGeorge]

The wag is gone, and now I'm just trying to dial in the gain. I started at 60% using the GEAR channel and had drift so I've been raising it little by little. I'm now at 75% with still an ever so slight drift to the left, maybe an inch every 3 seconds. I just hope I find a sweet spot and that it doesn't go straight from dirfting to wagging. As for the tail servo, it definately gets hot now that I can hover through an entire lipo. I have it mounted straight to the aluminum boom mounts. Should I use something softer inbetween the mounts and the servo flanges? I mounted the gyro using just one of the thicker 3M pads that came with it. I don't have enough room to mount it with the metal plate and 2 pads or I would have done that right off the bat.

It seems to be pretty solid. Quick and short rudder movements with the stick produces a very sharp and bounce-free rotation on the heli. It's like the tail runs into a brick wall, so I'm definately happy with that. Just a little more fiddling with the gain setting and maybe trying any suggestions to keep the little Henge servo cooler and I should be set.

Thanks.

[Jomaba4308]

I maidened my mini titan yesturday with the GA250 gyro paired with a JR DS290G tail servo. started at 65 gain and had severe tail sway which got a little better but did not go away completely even at 90 gain.