Replies to This Discussion

3D RoboticsPermalink Reply by Chris Anderson on November 29, 2009 at 12:39pm

No, you wouldn't use both. They do the same thing, via different methods. At the moment, the IMU is a stand-alone product and is not intended to work with ArduPilot.

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3D RoboticsPermalink Reply by Chris Anderson on November 29, 2009 at 12:54pm

Sure. But why? What does the Thermopile give you that the IMU does not?

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3D RoboticsPermalink Reply by Chris Anderson on November 29, 2009 at 1:03pm

Good answer ;-)

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Permalink Reply by Andrew Whipple on February 14, 2010 at 12:50am

how so? GPS isn't even mentioned in this post.

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ModeratorPermalink Reply by Morli on November 30, 2009 at 8:00pm

@Monroa,
Which is what I am hoping( PnP) for some day soon, :)) , best of both worlds

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DeveloperPermalink Reply by Doug Weibel on November 30, 2009 at 4:51pm

I like the Ardu too, but seriously, for a lunar lander???

Also, GPS only corrects the yaw in ArduIMU. You get no yaw information from the thermopiles, so actually no GPS is not a good reason to use thermopiles in conjunction with ArduIMU. There may be other good reasons however.

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Permalink Reply by Andrew Whipple on February 14, 2010 at 12:59am

i assume u mean laser range finder, but that wouldn't help correct imu drift

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Permalink Reply by Pwar Gyi Sayar on December 7, 2009 at 6:06pm

Hi all,

I don't want to create unnecessary another topic. I just want to know a bit about IMU 6DOF razor (Red) from sparkfun, where it stated required 3.3V regulator. Not mentioned about Vrefs for gyro chips. Which I believe will require 1.23V right?? Funny thing is it is connected to OUT pins where LPF part and also connection for external Vref. I didn't give any to those pins as i was not aware. But It seems to be giving out correct zero rate value. So i don't really know if i need 1.23V ref or not. Can u suggest n e ??

Regards
PG

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Permalink Reply by Ken on December 7, 2009 at 7:22pm

Spell it with me: T H E R M O P I L E. One "h."

A thermophile is something which likes heat. For example, teenagers residing north of the Mason-Dixon line when spring break comes. Or certain, rather disgusting, little creatures living near undersea vents. Which may be the same thing...

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Permalink Reply by Daniel Wee on December 10, 2009 at 10:19pm

Don't forget - on the moon you will get different gravitational readings so your accelerometric code will have to handle that as well.

Daniel

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Permalink Reply by Ken on December 11, 2009 at 4:57pm

Yeah, there are quite a few things that are tough to test in the garage, tweak, upload, tweak, upload, eh!

I'm worried about cold spots -- deep shadows -- on the ground, and the rather abrupt ground to space horizon transition without any atmosphere. Mostly the former.

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Permalink Reply by Greg Fletcher on February 16, 2010 at 7:41pm

I don't think thermopiles will work on the moon. You would be seeing the moon's surface temp or the temp of space which I think is pretty low (3 deg K ?). This is out of the range of the sensors. This would definitely be something to consider, but impossible to test unless you above the moon. It might work just from the how much of the surface is in the field of view.
If I had the resources for a moon landing I would use a machine vision system to back up and correct the gyros. I hear visibility is all ways near infinity on the moon.
Check out the Paparozzi site. Some where they explain how thermopiles work for autopilots. IMHO you might just want to use a triple redundant system using higher quality gyros.
Who's has a big enough rocket to get to the moon, let alone into LEO?
If this is one of those tests I've seen in the desert, then it would work, but that would be cheating if it wouldn't work in space. :)

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