skookum

[rickn816]

The MEMS unit is an accelerometer.

Rick

[MrMel]

Quite sure there is two different things ;

Accelerometers
http://www.analog.com/en/mems/low-g-...s/product.html

Gyroscope
http://www.analog.com/en/mems/gyrosc...s/product.html

Both are MEMS, one can only detect rate changes (gyroscope) and one can detect gravity (accelerometer)

Below a good description on the difference

To explain the difference: While the Acceleration sensor measures LINEAR ACCELERATION (which is the CHANGE of speed), the gyro sensor measures ROTATIONAL SPEED (not acceleration).
It's important to always remember: Speed is the change of position (how fast am I moving from a to b ), and acceleration is the change of speed (how fast am I going from slow movement to quick movement, for example).
Both of these quantities can be linear, like "from here to there", or rotational, like "how much or how fast is this thing spinning"...


So, that's easy to understand: The gyro measures rotational speed. 0 means, no rotation around that axis, and a value of x means x degrees per second, fine. (You can also see the rotational acceleration, when you just look at the speed x changing: if it goes from to 100, you know the spinning has accelerated).


The big problem or feature with the acceleration sensor is gravity. Gravity is an acceleration towards the center of the earth. It's hard to understand at first why it is an acceleration, but that's not a problem right now. When using the accelerometer, you always get a reading of 1G pointing down. That's gravity, ok, no surprise.
This HELPs you when trying to sense tilting. Once you see the 1G pointing to the side somewhere, your sensor is "not straight" anymore. Much like when you hold a jo-jo or a pendulum inside a stopped car that is parked on a slope / hill. Even without looking out of the window, you can tell that the car is "not straight", if the jo-jo is not pointing straight to the ground.

So far so good. Now, when you move the accelerometer, you change its speed. And that's an acceleration. If you were in space, that wouldn't be a big problem. You could always tell you're changing the speed of the sensor (and hence the speed is changing it's position, if you want to put it that way), and you could work out where it is.

But now, on earth, gravitiy and the movement of the sensor mix, and it's hard to seperate them. If you see a picture of the inside of your car, with the jo-jo (pendulum) NOT pointing straight to the ground, you'd immediately think: Hey, that's a car parked at a slope.

BUT: It could also be a car on a perfectly level plane, accelerating....

This is just the beginning, behind all of this is plain physics (mechanics) :-)

And now, the last thing: Accelerometers can't detect rotations around their center. Basically the sensor doesn't notice this rotation as you don't move it along a certain length. You'd need a compass or a gyro to detect this rotation.

However, if an accelerometer is rotated, but not around its center -- you can detect that. If you were to grab the accelerometer by its cable and spin it around yourself (like a hammer thrower), you could detect that. It's just a bit more complicated (you'd get sinus-like accelerations on different axes)

[rickn816]

https://www.helifreak.com/showthread.php?t=76808

Rotational acceleration.

[MrMel]

Rotational acceleration.

??

Mems Gyroscope is a Gyroscope (20 dollar part), Mems accelerometer (2 dollar part) is a Accelermoter, they are not the same was what I mean, they call it Gyroscope as where accelerometer is a specific part.
You need both of them as a accelerometer cannot do gyro stuff, and gyro cannot do leveling like bailout.

[c_forthofer]

I dont know if this will claify anything but my understanding of these difference between these things is this:

A gyro monitors the motion of an axis, and depending on how its programmed it can stabilize that motion or hold that axis in a paticular orientation.

An accelerometer measures the RATE at which the motion of an axis is changing. I.e. how quickly the motion in a paticular axis is changing. Or in other words Velocity (how fast) is not what an accelerometer measures... accelerometers measure CHANGES in velocity.

Chris.

[flatin]

Originally Posted by c_forthofer

A gyro monitors the motion of an axis, and depending on how its programmed it can stabilize that motion or hold that axis in a paticular orientation.

A gyro(meter) measures change of rotational speed around an axis. It'a also called a rate gyro. A position gyro integrates rotational speed with time to get the position. Example: If you have rotated with 15 deg/s for 5 s, you have rotated to a position 15*5=75 degrees different from where you started.

An accelerometer measures the RATE at which the motion of an axis is changing. I.e. how quickly the motion in a paticular axis is changing. Or in other words Velocity (how fast) is not what an accelerometer measures... accelerometers measure CHANGES in velocity.

Change in velocity = accelleration. So yes, an accelerometer measures changes in velocity. The rate of change of velocity. It's measured along the axis. If we integrate acceleration with time, we get velocity. And velocity integrated with time gives distance. If you accelerate with 2 m/s^2 for 3 seconds, your speed is 2*3=6 m/s. If you move 6 m/s for 5 seconds, you have moved 6*5=30 meters.

With gyros and accelerometers in 3 axis, X - Y - Z, you can keep track of the position and orientation.

Take a look at this circuit; tri axis gyroscope and tri-axis accelerometer: http://www.analog.com/en/sensors/ine...s/product.html

[6sic6]

Skookum,
You mention that the first add-on will be GPS. Sorry if I've missed this, but are waypoint capabilities to be expected? tnx

[Slyster]

AND.... anymore clues on ETA?

[gpach]

I have 2 FBL heads sitting at the post office waiting for pickup (RJX for 500 and 700). The machines are sitting there waiting. I just put one on my 600 and decided to install one of my 360's. I have one unused 360 left but would rather install a 720.

Art, throw us a bone and maybe hint where you are at. Have you done preliminary release (beta). Anything.

[t2o]

Which ever comes out first the 720 or the Total-G I am buying and donating to inside- heli for a Radikal review!


There... that will get them moving!

Seriously though, the part about which ever comes out first is truth. My Predator 90 is waiting and ready for a controller.

[airnoob]

C'mon, don't make me beg.

Will it work with a DX6i and AR7000 or would I need a DX7?

I need to be ready for the blessed day.

[Slyster]

We know it will work with anything... since for FBL you only need a 1 servo swash.

[t2o]

The 360 had bank-switching and remote-gain so it is nice to have the extra channel of a 7 channel Tx//Rx if you are interested using those features. The 720, I believe uses the mini satillite recievers so your ar7000 won't be needed. But you will need the satillite and I guess an extra satillte also if its a larger heli.

On a side note the Total-G was rumered to be out late 2009, its getting late I think.

[rickn816]

Originally Posted by t2o

The 360 had bank-switching and remote-gain so it is nice to have the extra channel of a 7 channel Tx//Rx if you are interested using those features. The 720, I believe uses the mini satillite recievers so your ar7000 won't be needed. But you will need the satillite and I guess an extra satillte also if its a larger heli.

On a side note the Total-G was rumered to be out late 2009, its getting late I think.

Apparently is it more difficult to construct these little boxes than we imagined.

Rick

[t2o]

Originally Posted by rickn816

Apparently is it more difficult to construct these little boxes than we imagined.

Rick

Yea, you are certainly correct and in all truth, I would rather have it right, then have it right now.

These new features are wanted, in particular (for me anyway) the dropping of the Rx to clean things up and reduce connections. I have considered just bailing out and buying another 360 but then again....I'll wait