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Old 05-30-2013, 01:52 AM   #52 (permalink)
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Originally Posted by jeff88 View Post
I can't seem to find one that is an analog output. The MPU-6050 says "I2C Digital-output of 6 or 9-axis MotionFusion data in rotation matrix, quaternion, Euler Angle, or raw data format". Is the 'raw data format' not analog?
Other than superseded Sparkfun boards, I couldn't find one either (but I haven't looked particularly hard for one). Maybe you will have to use two separate (analog) boards or figure out how to use the I2C.

My interpretation of "I2C Digital-output" is that the output is only as I2C.

What about this one: L3G4200D It says it has the option to output in SPI. I've tried looking that up, but can't find if it is analog or digital. Would SPI work for me?
It's not something I have done but Arduino can use SPI:

Arduino - SPI

What does the wattage rating mean? Is it the max watts the resistor can handle? So if I happened to buy 1W, that would work (just be a little overkill)?
The power that the resistor can dissipate. Use P=V x I to get the power in Watts. V is the voltage dropped across the resistor. To continue with the earlier example, 5V supply, 3.3V dropped across the LED, 30mA current limit, no other voltage drops in the circuit:

P = (5-3.3) x (30/1000)

P = 0.051W

1W will work. What you may find is that not all of the standard resistances are available in each of (1/4, 1/2, 1W) the low power resistor types and 1W
will likely have a wider tolerance than the other types of resistor.

OK. As a side note, how does it determine the speed, the size of the wavelength?
Exactly that. At 50% duty cycle the time spent high = the time spent low so measuring the time spent high and doubling it gives the wavelength, which can be converted into a frequency.

There are a couple (that I know of) frequency libraries for Arduino around that makes it a bit easier to implement than doing it from scratch.

So something like this then?:
That looks good.

I was looking for a DMM on Amazon and of course, about a million different ones came up. I want an inexpensive one, but is there something I should look for?
At a minimum it should have that >10M Ohm impedance, other than that...

On a car most of what you will use it for is DC voltage and less than 20V.

Duty cycle is nice to have, as is a tach. function. DC frequency is a workable proxy for the tach. and vice versa (you can convert from and to a frequency using a low tension ignition signal and the firing frequency of the particular car, or from a sensor signal).

Some ignition, wheel and road speed sensors do put out an AC frequency signal so that would be useful also.

3.5 (0-1999) or 3.75 (0-3999) digits is enough.

Somewhere between $20 and $60 is probably about right.

Any idea on what size veroboard I will need (approximately)? Would a 2x3" board be big enough?
It depends upon what you want to mount on it. I'll attach a circuit board image for a dual 7-segment display as an example. (Also, a schematic of a display circuit using the 4511. The resistor values are typical but you should check them for yourself.) A good standard hole spacing to use is 0.1". 5 holes (with the wires passing through holes 1 and 5) will be about right for a (1/4;1/2;1W) resistor or a diode.

You might prefer perfboard instead. It depends upon what you find easiest to use (which can in turn depend upon the particular project).

You can cut the boards to size with a fine toothed (~30+ tpi) hacksaw.

Originally Posted by IamIan View Post
?? I don't see how it could possibly tell the difference ?? ... From it's point of view force is force in x direction is force in x direction ... be it Gravity ( incline ) , or vehicle ( sensor ) acceleration.
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