Smallest piezo gyro

[peterbennett26]

Has anybody got a circuit for an ultra lightweight piezo gyro, and a link to theory of how they are implemented in helis?

I will do some searching on the topic and post to this thread.

Success to the forum!

Pete

1st link http://www.sensorsmag.com/articles/0203/14/main.shtml

[JohnnyB]

Tokin CG-16D
Murata ENC-03M
Analog Devices ADXL202

Are possible components.

Johnny

[Comatose]

ADXL202 is an accelerometer. I use a pair in my UAV project, but not a gyro. Its a force/tilt sensor

[mmormota]

I think so that the modeler's "gyro" is working with piezo accelerometers, and not gyroscope at all.
The polysilicon accelerometer, like the adxl202 is more accurate (and more expensive) then a piezo accelerometer.

[jeffs555]

The analog devices "gyros" are ADXRS150 and ADXRS300, which are polysilicon angular rate sensors. The ADXL202 is an accelerometer.

What is used in hobby "gyros" are piezo angular rate sensors, not accelerometers.

Jeff

[peterbennett26]

The aerohawk heli uses a Murata ENC-03J which is a Coriolis effect gyro.

I have not worked out the circuit yet as it is shrink wrapped together with the radio receiver etc. etc. The board(s) is their copy of the all-in-one picoboard as used on the Piccolo.

I have learnt something of how it operates from this webpage:-
http://www.cim.mcgill.ca/~mcmordie/Thesis_html/GyroThesisChapter.htm

Pete

[JohnnyB]

Found something on the gyro principles here:-

http://www.w3mh.co.uk/articles/html/csm7_8.htm

[KeithK]

Does anyone know where I can get a 5volt gyro like the Tokin CG-16D? I need to repair a Roswell Flyer.

Keith

[JohnnyB]

3 volt gyro chips are available. Would those do?

Johnny

[KeithK]

3V would be do-able on the input side, I could add a V regulator or resistor, but the output is also less voltage. That would require a lot more work figuring out the gain circuit. I think I will just hope for a 5V to show up somewhere. I hear some of the old hand-held mice/pointers used a couple 5V piezo's that will work. THey show up at computer meets. Also the old Piccolo heli board used a 5V. Heard they might have dropped in a 3V version without mods and caused a lot of failures.

Keith

[mattweisz]

Has anyone used the ADXRS150 and ADXRS300 gyros from Analog? I would like some advice on where to buy them, especially the Evaluation Boards. I tried Analog's website, but they're out:(

matt

[Mr.RC-CAM]

ADXRS150: 124 pcs in stock at Digi-Key, $50 each.
ADXRS300: 13 pcs in stock at Digi-Key, $50 each.

RC-CAM

[mattweisz]

Thanks -- I found the evaluation board on digikey, but they want $75, which is kind of steep when you can get it direct from analog for $50 ( if they ever get them in stock)

oh, btw, I am going to use the gyro along with an ADXL202 and BasicX-24 to make a kalman filter. Eventually, I would like to put it on my Dandy Sport:)

[mattweisz]

To my surprise, 3 Analog Devices ADXRS300 Evaluation Boards showed up today in the mail. These weigh about 4 grams a piece. Even better, they were free since Analog Devices gives samples to Colleges! To top that, they sent them Next Day Air UPS ( also free )

Here is a link to their website ( just do a search for adxrs300eb on their site)

http://www.analog.com

I'll report back when I get time to test them.

Here is a pic

http://www.sander-electronic.de/adxrs300eb.jpg

[Comatose]

Wait, what???

I had to pay for mine. Of ocurse, that was last year. If analog has moved to free sampling their gyros... well... that'd make my happy. Gotta get the details of this one. CAn you give me a step by step of where you cicked/filled to get these free? Not working for me. I get accelerometers from ADI free from time to time, so I know their "normal" system.

[mattweisz]

I got my samples through the College Parts Program.

Quote from their website
---------------------------------------------------------
"Analog Devices' University Relations program has made it a priority to Parts Program to enhance the hands on experience of students and acquaint them with our products before they become either our employees or our customers."

-----------------------------------------------------------------

Here is the link to submit a request:

http://forms.analog.com/Form_Pages/corporate/parts.asp

[TMorita]

Kinda funny I should stumble across this thread.

About two years ago, I spent a lot of time thinking about how to implement a gyro using an accelerometer like the ADXL202.

It's been a while, but I think it required three accelerometers.

You need two about an inch or two apart to deduce the angular velocity in yaw by measuring the relative acceleration. Think of the gyro unit yawing relative to some center, and the two gyros will describe two concentric arcs.

You also need one accelerometeter at right angles to the sensing plane to factor out gravity if the sensing plane tilts.

Maybe someone has a better solution, but I came to the conclusion it was cheaper to use a proper gyro that can sense angular velocity.

Toshi

[Comatose]

Most of what we're talking about using an accelerometer for is using it like an attitude gyro (measuring gravitational acceleration). For true gyros, there are the MEMS angular rate gyros. Angular accelerometers (what you described) exist as well, but angular acceleration isnt generally as useful to sense as angular rate.

[mattweisz]

I tested out the ADXRS300 EB and I am impressed ( this is my first experience with gyros of any type)

My A/D converter is only 10 bits, giving a resolution of .0049 mV -- ( .005 mV corresponds to 1 deg / s ) so it looks like I'll have to decrease the measurement range to something like +/- 200 deg/sec in order to get more resolution. Has anyone done that?

Also, has anyone make a kalman filter using a microcontroller, an ADXL accelerometer, and a ADXRS gyro? Any help would be appreciated

Thanks,

Matt

[Monster]

Thanks Mattweisz from you Minneapolis neighbor :) I did not know about the free samples that Analog devices offers to colleage students. What I do know, is that they are not offering their MEM’s Gyro’s as free sample to the general public.

For Mattweisz:
There is an open source project on the web for autonomous heli flight. They use an Atmel processor, some Tokin rate gyros, and ADXL202’s to make a IMU. They have code posted for the AVR (GNU GCC C compiler). They have use a Kalman filter in the Atmel. Look on the links below for a C filter/Kalman file. The founder of this open source project also started his own business, Rotomotion. There is a Kalman filter C file also posted on that web site.

http://autopilot.sourceforge.net/
http://autopilot.sourceforge.net/download.html
http://www.rotomotion.com/prd_REV2.4.6DOFK.html
http://www.rotomotion.com/downloads/tilt.c
http://www.rotomotion.com/downloads/tilt.h




For KeithK:
Rotomotion, a company started by the open source “auto pilot” people mentioned above use this Tokin gyro in their designs. I think? They used to sell them separately on there web site. You should call them.

http://www.rotomotion.com/contact.html

[peterbennett26]

This guy repairs Piccolo picoboards and one of the components he can supply you separately is the gyro chip:-

maybe cheaper?

www.pgoelz.com

[lloydkoh]

Hi!!! Does anyone know of any reference to how ADXRS300 operates. I am required to implement it into my project. Have been reading through the datasheet but its too complex for me.

Any idea of any sites/manuels that explains in a simpler way?