# Inexpensive yaw rate (azimuth) sensor distributors?

#### Cliff_J

Anyone know of a place to find an inexpensive yaw rate sensor? Thinking about maybe picking out a sensor from a Stabilitrac Cadillac in a salvage yard (new price is over $200, hopefully salvage yard wouldn't even know price and sensor would've survived crash) but it would be even nicer to find a distributor that had one on an eval board for only 300% markup over the expected quantity price of$10-20.

Mouser has 3 axis accelerometers for cheap and I've thought about using two of them as a crude yaw sensor (via the difference in lateral acceleration of the front and rear of the vehicle) but this just seems very error prone in comparison to a self contained package.

Any ideas?

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#### dlgoff

Gold Member
I don't know if this will do what you want, but Hobby-Lobby has a few gyros used for RC aircraft. The IK0611 Ikarus Tele-Gyro is used for yaw control.

Regards

Don

#### faust9

Cliff_J said:
Anyone know of a place to find an inexpensive yaw rate sensor? Thinking about maybe picking out a sensor from a Stabilitrac Cadillac in a salvage yard (new price is over $200, hopefully salvage yard wouldn't even know price and sensor would've survived crash) but it would be even nicer to find a distributor that had one on an eval board for only 300% markup over the expected quantity price of$10-20.

Mouser has 3 axis accelerometers for cheap and I've thought about using two of them as a crude yaw sensor (via the difference in lateral acceleration of the front and rear of the vehicle) but this just seems very error prone in comparison to a self contained package.

Any ideas?
Most accelerometers can detect their orientation by measuring the acceleration due to gravity so one would suffice. They are actually quite accurate as well.

#### Cliff_J

faust9 said:
Most accelerometers can detect their orientation by measuring the acceleration due to gravity so one would suffice. They are actually quite accurate as well.
I'd thought about that too, but many of the manufacturer's of the gyro stabilized yaw sensors note that vibrations can severly limit the data rate using only a gravity reference, that the low pass filtering required limits the data to like 5Hz or less. Of course I'm still trying to figure out how a tuning fork is similar to a gyroscope enough to label it that way...but the literature is pretty convincing on both counts. I'm also not sure how much of that potential FUD is in the incliometer realm but not in the realm of yaw.

And how would one accelerometer measure yaw? Roll and pitch make sense with a 3-axis, but I'm drawing a blank on how yaw would be determined.

dlgoff - do those devices just adjust the PWM signal to the servos to try to maintain heading? So I could just send in a simple fixed-width pulse and measure the output width to deduce the yaw? I also couldn't find the 611 but they have a 613 that sounds like it does yaw as well.

#### dlgoff

Gold Member
Cliff_J said:
dlgoff - do those devices just adjust the PWM signal to the servos to try to maintain heading? So I could just send in a simple fixed-width pulse and measure the output width to deduce the yaw? I also couldn't find the 611 but they have a 613 that sounds like it does yaw as well.
I've never used any of these devices but I think you're right about them adjusting the PWM signal. From catalog 38 discription, their sensitivity can be controled from the transmitter. And it "...has automatic fading which gives strongest heading control when transmitter control stick is in neutral...".

This old catalog also has a 612 (for 2 aileron servos) for $84 and a 615 (extreme tiny) one for$65.

Regards

#### faust9

Cliff_J said:
I'd thought about that too, but many of the manufacturer's of the gyro stabilized yaw sensors note that vibrations can severly limit the data rate using only a gravity reference, that the low pass filtering required limits the data to like 5Hz or less. Of course I'm still trying to figure out how a tuning fork is similar to a gyroscope enough to label it that way...but the literature is pretty convincing on both counts. I'm also not sure how much of that potential FUD is in the incliometer realm but not in the realm of yaw.

And how would one accelerometer measure yaw? Roll and pitch make sense with a 3-axis, but I'm drawing a blank on how yaw would be determined.

dlgoff - do those devices just adjust the PWM signal to the servos to try to maintain heading? So I could just send in a simple fixed-width pulse and measure the output width to deduce the yaw? I also couldn't find the 611 but they have a 613 that sounds like it does yaw as well.
My team uses these on our race car. The car's data acq system is not mine(I do engine controls) but I know we use a few accelerometers to determine evrey conceivible aspect of the cars orientation as well as suspension system orientations. I'll talk to the person who actually works with these to see what he has to say.

A yawing motions will still producing an acceleration about a vehicles CG though so an accelerometer would be able to determine the yaw based on the acceleration detected.

#### Cliff_J

dlgoff - your're speaking my langauge, those prices look nice.

faust9 - thanks, accel about the CG makes sense. Anything you can find out from the data acq guy would be awesome.

I'd love to just buy a vbox (and a tire pyrometer) work on car setup and driving skills but that money could buy a nice set of coil overs (ok, no motec or anything but the Ground Control shocks look attractive with comp/reb knobs and rebuild/revalve ability) and I'd like to think I can try to do it on a beer budget with a laptop and basic data acq. Maybe I'm just throwing more mud at a teflon wall and I think I should first figure out how to make this a business instead of an expensive hobby...

Also I'm thinking maybe I should offer to take out the trash at night up the road at Panoz and see if they throw away anything useful. LOL

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