SparkFun Forums

[justincoty327]

I am using the ITG-3200 Sparkfun Gyro and am wanting to obtain the rotation of the wheel. I plan on placing the gyro in the center of the rim, and obtaining the z-axis reading. However, I am not sure how to do this exactly, or if this is the best way to do so. It is going to be placed on a racing quad so the rpm's will be rather high. I am then going to use the rpm's to calculate the wheel horsepower and torque and log it to an sd card. I am just not sure how to go about reading the z-axis and converting that reading into actual rpm's. Can someone please help me with some basic code. I am new to electronics, but not programming. I know several programming languages, HTML/CSS, Visual Basic 6, VB.NET, C++, C#. I know logically what to do, I just don't know a lot about sensors. Thank you all in advance for the help.

[skimask]

Or...put a hall effect sensor on the half shaft.

[justincoty327]

Well I just realized that I misread the formula for torque and hp. Seems you must know the rpm and either the torque or hp to calculate the other. So now I am stuck trying to figure out how to either determine the torque or hp.

[Ross Robotics]

I assuming this is for a school project and you have to use a gyro??

[justincoty327]

Nope, its for my own entertainment. I have no actual dynos that I can go to around here, and I race and tune drag atv's. Which is hard to do without numbers. So I am trying to find a way to create a portable dyno.

[Ross Robotics]

Then why are you so determined to use a gyro? There are simpler ways to get the end result.

[justincoty327]

I assumed it would be the easiest considering it calculates the angular velocity of the z-axis which can be directly formulated into rpm's.

[skimask]

Or put a hall effect sensor on a driveshaft...or multiple hall effect sensors on a driveshaft

RPM = measure time between pulses on the hall effect sensor. 1 hall effect sensor = 1 pulse per second = 60 RPM, 2 pulses per second = 120 RPM...and so on...

Or use a gyro...

RPM = a crazy bunch of math calculating the angular velocity of the z-axis of a gyro, assuming your sample rate is fast enough (read that as VERY fast), your math precision is tight enough (easy on a PC, not so easy with an arduino/etc), and the gyro's sensitivity thru all ranges would be linear enough (it won't be).

Easy for me, easy for a bunch of people...on paper...
Not so easy when you end up limited to a handful of bits, single precision math, and some tables using linear interpolation.

Now which method do you assume is easier?

[justincoty327]

You all are really up tight lol I just wanted to do something on my own to be honest, Im no engineer, I can program and thats it. Just wanted to have some fun, but heck Ill just buy one.

[Ross Robotics]

Not uptight about anything. You have to understand that we have "children" who post in here thinking that their projects are easy but don't want to do the work. It's rare to have someone that is willing to start a project like this and see it till the end. By all means, go for it. If you have any issues, please ask for some help with it.

[skimask]

<"children"> lol
eg. students of all ages. rofl

Maybe it's going to be a Rube Goldberg tire rotation sensor. lshism
(only because I absolutely hate "lol" and "rofl")

[justincoty327]

Well by no means am I a child. I have three college degrees. I am working on my fourth right now. The only reason I placed lol in there is to try and break the tension a little. All I am saying is that you all came off a little up-tight. I clearly stated I was no engineer. I have programming experience but thats it. I develop programs using c# in visual studio. My software coding is more computer based, not hardware based with sensors. I just had an idea and wanted to run with it. Not trying to be the next millionaire or anything like that. There are no dyno's in this area. So thats why I want to create one that I can use.

[satacoy]

Read up on "rotary encoders". That's what I've used in the past to determine RPM.

[Valen]

Even if the conversion of the gyro signal to RPM was possible (theoretically it is) and computationally efficient (not really), I would foresee many a problem in getting it fixed to the wheel and not fly off on high RPM, providing it with power or getting the gyro data off the wheel without wires getting tangled around it. I don't mean to put you down. But that's not the way to go.

Getting torque data is equally hard, as it can only be measured inside the wheel-, gear- or motor-axle when the quad is driving. You need some kind of strain-gauge sensor on it. Which has the same problems as indicated above. Is your intend to get the data while the quad is on the road, or even on an off-road track? Or do you intend to sample your data on a static quad setup, with some form of external mechanical load like a rolling bench (or more for engine performance testing: water-brake) ? Obviously the on/off-road situation is a lot harder to do. Getting the sensor away from the quad, so on the external load (bench/brake) would simplify things a lot.

[Valen]

p.s. What's a "dyno"? Other than the extinct ones, that don't fit the context.

Nevermind: dynamometer , https://forum.sparkfun.com/viewtopic.php?f=42&t=40686

I guess there are more ways to skin this cat than straingauges.