PG-03 Gyro inside?

[Midas]

Hi folks,
I ordered PG-03 gyro some days ago, now I'm wating for it. In the meanwhile I have a question: have anyone tried to place the gyro inside of Robonova? Actually I don't like how it appears on the left shoulder.
I'd like to remove its case and then find a place inside of the robot...

(Sorry for my English, it's not my native language).

[visuvius]

I just installed a PG-03 and I can't really see how anyone could fit it inside the RN1. I had trouble with mine and in my forum post another member said they removed the plastic top off of the gyro to get it inside the RN1. Even with that, I still don't see how they crammed it in there while maintaining its horizontal placement.

I'm sure its possible, probably just takes some work.

[Tim]

Hi Guys

Never say never!!

I've got two PG-03 inside RN-1.

You have to take the case off (the manual refers to the case-off weight and I presume some aeromodellers need to do this for small models so AFAIK its just fine). I soldered a single wire to the signal out pin so that there are only four wires running to each gyro. I then covered each gyro in electrical tape (nice clear heatshrink would have been better) with carefully pre-cut holes to allow sight of the LED and access to the two screw adjustments. Then, just use the foam mounting pad...

The pitch gyro is in the left front chest cavity. I had to take the shoulder servo mounting out of the cavity to ease the process of mounting the gyro on the foam on the servo itself. Once RN-1#s arm is reassembled, you can see the LED and adjustment screws through the cutout on the chest bracket. You can put the front cover back on once you've tweaked things up.

The roll gyro is in the head. You have to change the way you mount the LED in there - mine now sits don top of the two brackets that it was originally screwed to (and uses a spare wire tie to hold it there). I used velcro in addition to the foam mounting pad so that I could easily remove the gyro to get at the two head mounting screws. You have to leave the back of the head off whilst adjusting this gyro.

Happy to post photos when my camera comes back from the shop. It is not worth posting the ones from my camera phone - it couldn't focus that close! In the meantime, any questions, fire away.

Cheers
Tim

p.s. there may be some temperature stability issues but so far no sign of them.

[Midas]

Oh, great! Thanks Will try to do my best as soon as the gyro arrives.
Would be great to see your photos, Tim

[Tim]

Midas

good to see that enthusiasm

I've posted my camera phone pictures - apologies for the quality go without saying.

(1) This is the pitch gyro after mounting on the shoulder servo.



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(2) This is the pitch gyro - you can see the LED as well as the gain and setup screws through the chest plate cutout.



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(3) This is the roll gyro in the head. Note the use of velcro so you can easily get to the head mounting screws in the neck area.



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Hope those help

Cheers
Tim

[engineer]

hi, there's a set of posts about installing gyros in rn-1 you've got the gyro in the chest monitoring the z axis not f/b. the gyros, without the cases fit above the shoulder servos I put them there cause i wanted to give RN-! multicolored led's for eyes. stillworking on them.

[Midas]

Tim, thanks again for the detailed explanations! You even had to disassemble the robot Really appreciate.

[Tim]

Midas - my pleasure.

Engineer - your post got me thinking. I had always "just assumed" that gyros were fairly insensitive to gravity, so that all that mattered was the orientation of the rotation axis to which it is sensitive.

In my case, I've just rotated the gyro board 90deg about the sensitive axis, so it should still be sensitive to the same rotations as the shoulder mounted device. The problem I figure you were getting at was, are these boards compensating for gravity and therefore need to placed flat like on the shoulder? That's an interesting question . . .

If these things were sensitive to gravity (i.e. like an accelerometer, gravity = acceleration) I would have thought they'd be no good in helicopters during aerobatics (but they seem to be ok, not that I'm a model heli pilot)

So . . . just to check things out, I popped open my RN-1's head and looked at the sensor chip in the PG-03. A little detective work shows that it is made by Murata in Japan

And from their website . . .

This product is an angular velocity sensor that uses
the phenomenon of Coriolis force, which is generated
when a rotational angular velocity is applied to the
vibrator.
Murata's original, small ceramic bimorph vibrator and
simple Cap-Base structure realize their ultra-small
size, about 0.2cc. Their small and lightweight shape
increase flexibility of installment and help your
apparatuses to be downsized.
They are surface mountable device, can be mounted by
automatic surface mounter.

Analog devices have a nice page about this class of gyro, and they say

It should be noted that the gyro may be placed anywhere on the rotating object and at any angle, so long as its sensing axis is parallel to the axis of rotation.

So that says to me that the chest mounted gyro does the same job as the shoulder mounted gyro, assuming that their sensitive axes are parallel, and gravity be damned. No doubt they are sensitive in some small, negligible way but we at least can overlook it by the sounds of things. I suspect temperature drift from being next to a hot servo is going to be a worse problem.

I did look at putting the gyro in the shoulder cavity but suspect I decided that I wanted enough room for the foam pad too or better access to the adjustment screws (can't remember now). Anyhow, either place is out of the way and therefore good .

Cheers
Tim