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Old Sep 21, 2010, 04:17 PM
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Gyro advice for a DIY gimbal

Me and a friend have been working on an aerial photography set up for a while now. One of the main things we are struggling with is getting the gimbal gryo stabilised. I bought a hobby king HK401 gyro but cant seem to get it to work the way I want.

When connected to the servo controlling the roll axis it reacts when I move the gyro quickly but not slowly. I don't know if I'm using the wrong type of gyro or just trying to achieve something on a budget that isn't possible with gyros that cheap.

Any guidance would be appreciated!

Link to the gyro I have
http://www.hobbyking.com/hobbyking/s...dProduct=10113

Video of what I'm trying to achieve (but just with the roll axis and mine isnt a 360 design)
http://www.youtube.com/watch?v=Hptwk...ext=1&index=43
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Old Sep 21, 2010, 04:31 PM
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Hellsiege's Avatar
United States, CO, Colorado Springs
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I don't have any on the roll axis just pan/tilt as I have a 2 axis gimbal but I'm using one 401b and one real 401 on it. The trick for me was very low travel adj range (30 on each end) this slowed the robotic servos down to a point the gyro started working (in rate mode, not HH and again low gain settings until I got it tweaked). Took a few hours or testing and playing around with it before it started working. My breakthrough point was reading how the gyro needs to be in rate mode vs heading hold.

Video with a quick demo test of how they work (skip to 3min or so mark) - I don't make demo videos too often and you can tell why lol:

Stretched Align Trex 600 AP rig (4 min 0 sec)
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Old Sep 21, 2010, 04:38 PM
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Quote:
Originally Posted by Hellsiege View Post
I don't have any on the roll axis just pan/tilt as I have a 2 axis gimbal but I'm using one 401b and one real 401 on it. The trick for me was very low travel adj range (30 on each end) this slowed the robotic servos down to a point the gyro started working (in rate mode, not HH and again low gain settings until I got it tweaked). Took a few hours or testing and playing around with it before it started working. My breakthrough point was reading how the gyro needs to be in rate mode vs heading hold.

Video with a quick demo test of how they work (skip to 3min or so mark) - I don't make demo videos too often and you can tell why lol:
Thanks for that, I was worried that I was never going to get it to work but this has given me hope! Sorry if this is a bit of a stupid question but I am a bit new to the gyro scene. How do you change it to rate mode instead of heading hold (on the 401b). Also did you have to do the 401b mod I've read about which involves taking the gyro apart and putting foam in?

Impressive set up by the way!
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Old Sep 21, 2010, 04:43 PM
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Thank You - I did mod the 401 but only because it's so simple and it really does make a difference. Have modded over 20 now for customers w/out issue and not a single return so pleased with the 401b's. To get the gyro into rate mode you lower the gain to less then 50%. You'll know it's in rate mode as the red light will go out. It's confusing as I never fly helicopters in rate mode so hardly used it, but to get the gyros to do what I want my gain is low in the 30 range and endpoints depending on servo are 20-30. You'll use the travel adj on whatever channel you have the remote gain wire plugged into - when you need to make adjustments to the gain etc... Works the same as a gyro menu you'd see if you had a radio in heli mode with GEAR/Gyro mapped. Hope this helps,

Steve
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Old Sep 22, 2010, 06:41 PM
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Ok might have a few things wrong here but I'm still only getting reactions when I move it quickly. If I jerk the gimbal in one direction the gyro reacts and moves the servo correctly but returns back to center almost straight away. It doesnt seem to hold like yours does in the video.
If I tilt the gimbal gradually the servo doesn't move at all.

I've got the Gain plugged into channel 6 with an end point of 30%

The gyro is plugged into channel 3 also with end points of 30%

The delay is set to about half but doesn't seem to make much difference wherever I put it

The limit is set to bottom but if adjusted up also doesn't seem to help in any way

It's driving me mad so any help would be appreciated!
Have done the 401b mod too and gyro is mounted on double sided sticky foam
Thanks
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Old Sep 22, 2010, 07:37 PM
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Are your servos modded for continuous rotation? If they're not, they'll always want to return to center
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Old Sep 22, 2010, 07:42 PM
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Quote:
Originally Posted by Lost In OC View Post
Are your servos modded for continuous rotation? If they're not, they'll always want to return to center
Exactly, I'm using Continuous Rotation servos and like Lost said if standard they won't work.
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Old Sep 22, 2010, 10:15 PM
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Ah, bit of a major error on my part there then. Yes I'm using standard servos. How do you mod a servo to become continuous or are they any you can recommend out of the box?

ETA
Would this do the job? Seems a reasonable price and its a UK supplier
http://oomlout.co.uk/servo-continuou...ion-p-235.html
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Old Sep 22, 2010, 11:26 PM
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Those are CR and do look like they'd work if the rest of the servo specs match your application. HS-1425cr is a servo I've used and then the CR servos from photoship one that came with my 2xpt mount. I haven't had issues with either, but once again I think the ones you posted will work just fine as well.
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Old Sep 25, 2010, 05:15 PM
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Servo arrived today, its nearly there but the resting point when the gimbal is level seems to move slightly more every time the servo moves to compensate for roll. Which adjustmrnt would be affecting this?

Thanks for all of your help so far, I wouldn't have got this far without the both of you!
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Old Sep 25, 2010, 07:06 PM
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I'm not 100% sure I understand, but thinking your refering to the servo not stoping when gimbal is level. You'll have to play with the trim/subtrim to get the servo to stop. If it never stops, try lowering the gain as it may be too sensitive still on that gyro etc...
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