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1  Using Arduino / Sensors / Re: Distance Measuring sensor on: March 25, 2013, 05:52:18 am
I think you might need two (or more) to cover this sort of range.  I haven't seen one that can cover as far out as 10m and still get back to a very small measurement like 1cm. 

What sort of resolution is required?
2  Using Arduino / Sensors / Re: Tilt sensor question on: March 24, 2013, 08:11:33 pm

It can resolve the difference made by slipping a piece of paper under one corner of the board.

As small as this device is, it better be capable of that if I'm hoping for 1/10th degree resolution. smiley-grin

It probably doesn't belong in this section of the forum, but I'm currently reading to try and figure out if my Arduino Pro Mini 328 has enough on-board memory to log a few shots from the magnetometer and tilt sensor.  I'm trying to fit all of this hardware into a tiny space.  It's not impossible, just more design consideration and machine work on my part.  I was planning on mounting all of this in a Delrin housing I will machine on my lathe and mill, and then cartridge that into 316 stainless steel housing that will be water-tight (That's right, going underwater, Jack smiley-wink).

I'd like my apparatus to be able to go into an obscure area (under-water), take about 3 samples from each sensor, and store it to the "satellite" arduino.  I'll retrieve the data from the "satellite" arduino via a "mother" arduino or computer when I get it back to the surface.

Reading about storage is like a different language to me, but I'm learning (slowly).  Can this amount be stored on the Arduino Pro Mini 328, or do I need to implement a micro-SD portion as well.  Thanks for the help.  I'm sure it would save me hours.

I'm real excited to get this project into building mode, and I sure appreciate the help I've received thus far.  Good day.
3  Using Arduino / Sensors / Re: Tilt sensor question (Solved) on: March 24, 2013, 08:31:41 am
That sensor is an accelerometer isn't it?

Yes sir, and that's my point.  If I used the accelerometer we've been discussing teamed up with say a HMC5883L, I should be able to read inclination up to 15 or 30 degrees and know which direction the tilt is.

I could also use the accelerometer to tilt compensate the HMC5883L.

4  Using Arduino / Sensors / Re: HMC5883L Calibration? on: March 23, 2013, 02:28:29 pm

Explains declination adjustment, tilt compensation, etc.
5  Using Arduino / Sensors / Re: Proximity detection hardware suggestions needed on: March 23, 2013, 11:38:46 am
Yes, i'm trying to sense the fingering of a trumpet.

It's helpful when you let us know what you're working with.

I'm with Michinyon.  I'd recommend hall effect over reed switch; no moving parts = never wear out.  Mount hall effect in cap, fasten magnet to bottom of valve.  Proximity in which the sensor will "see" the magnet is entirely dependent on the magnetic strength of the magnet itself.  I buy my neodymium (rare earth) magnets from K&J magnetics, and they supply the gauss of each magnet on the website.  Compare to hall effect datasheet to see which magnet you need.

I use these hall effects from digikey...

If you go this route, the sensor only reads the south pole of a magnet.  Also, the data sheet is full of different applications these devices can be used for.  Really neat little device.

6  Using Arduino / Sensors / Re: Proximity detection hardware suggestions needed on: March 22, 2013, 03:27:38 pm
I'm not real familiar with the little infrared sender/receivers.  I have a few, but only know what I've read.  Like I mentioned, the only thing I've read that they're bad about is sunlight affecting them.  I have a phototach that I use to measure the rpm's of engines off the harmonic balancer.  If it's a sunny day, especially if there's a shiny spot on the balancer, it will make trouble for the phototach, which I believe is just a IR sender/receiver and a timing circuit in the inside.

However, I don't see how this would be a problem for you.  It's dark in there.  Plus, it's hard to beat the $2 price on the one I gave the link to.  You could rig that whole deal up f/ less than $5.

However, sparkfun also provides a setup already on a breakout board (grunt work already done)

Read the datasheet and see if it will work
7  Using Arduino / Sensors / Re: Tilt sensor question on: March 22, 2013, 03:11:54 pm
OK, so I would still only need 6 I/O pins from Arduino to talk with 3 sensor via SPI?  I would just have to check the data sheets to get the addresses of the devices programmed correctly.  Very good.

I'm also trying to decide if I need a gyro at all.  I've read and read about gyro's and can't seem to understand why you would need one with an accelerometer...for my application where I am measuring the angle of inclination in a static situation.

If I just want to know angle of inclination and which direction that angle is, can't I get it done w/ a low-g accelerometer and magnemometer?

8  Using Arduino / Sensors / Re: Sensing mechanical alignment on: March 22, 2013, 02:54:18 pm
I don't mean to de-rail the whole plan here but would it be possible to have a spring between the solenoid plunger and the pin, run the detection apparatus you described, and fire the solenoid a little early?  The spring pressure between solenoid and pin would cause the pin to drag across just outside the hole, but you don't have to be near as accurate.  The moment the holes are perfect, the tapered pin should seat completely, or engage completely.

Or, depending on what type of material we're talking (I'm assuming steel), it might not hurt to not even run a spring and just engage the solenoid early.  If the pin is made out of 4140 pre hard, it won't hurt it just dragging across 1018 mild steel.  Might make a groove in the mild steel, depending on how many times you're planning on doing this; and how much force the solenoid is applying.  If it's a lot, you could put a bronze 660 tip on the pin.

Just a thought

9  Using Arduino / Sensors / Re: Proximity detection hardware suggestions needed on: March 22, 2013, 01:23:02 pm
Perhaps using an infrared emitter / detector pair would be cheaper / easier.  Since it's enclosed, ambient light is a non-issue.

Here's the schematic...

Are you planning on doing a little machine work to the cylinder cap to mount whatever you decide to do, or what?
10  Using Arduino / Sensors / Re: Tilt sensor question on: March 22, 2013, 01:06:36 pm
I appreciate the help.

This part is one piece of the puzzle.  I am having to build my own IMU which will include a magnetometer and gyroscope.  If I'm understanding pg.10 of the datasheet correctly, each of these devices can share the data in, data out, and serial clock lines, right?  The chips would be SS0, SS1, and SS2.  Is this how SPI is intended to function?

11  Using Arduino / Sensors / Re: Tilt sensor question on: March 22, 2013, 12:44:27 pm
Thanks Mike.  I have no experience with SPI, but a wiring diagram is provided at the bottom of the datasheet.  Would you recommend using the 5v output of the Arduino to power the device, or would it be too noisy?  Or, is that only an issue in an analog setup?  I reckon I can figure out the rest of the connections to Arduino from the playground.
12  Using Arduino / Sensors / Tilt sensor question on: March 22, 2013, 12:28:10 pm
I am considering buying one of these little smokies...

I need a tilt sensor that can measure within 1/10 of a degree of accuracy.  Everything looks good, however I noticed that the information from the chip is sent via SPI in 11-bit.  It's my understanding that the ADC on my Arduino Pro Mini 328 is only capable of 10-bit.  It appears to me, if you look at the chart on pg. 13, that the 10-bit capability of the Arduino will limit me to only half the resolution of the sensor, as 1024 is at 0 degrees.  Therefore, I can only read positive x, but not negative x; positive y, not negative y.

I hope I'm just not understanding something correctly.  I've had a tough time finding a low-g accelerometer that will mate nicely w/ my 5v Arduino.  Thanks in advance.
13  Using Arduino / Sensors / Re: Autonomous Lawn Mower Navigation on: March 22, 2013, 12:18:41 pm
Perhaps you could use one of these to cover the differential aspect.

I would imagine with some basic calculus programming you could at least know fairly accurately your relationship
with your starting point or any other via you have exact coordinates of.

I read quite extensively about this IMU until I realized the accelerometer wasn't accurate enough for my project.  Seems like a pretty good product.
14  Using Arduino / Sensors / Re: Trigger level of water in a small glass tube on: March 22, 2013, 12:11:39 pm
I would suggest a hall effect sensor.  Place a rare earth magnet inside the tube in something that floats, cork or whatever, and mount
a hall effect sensor on the outside of the tube.  Put one hall effect up top and one on bottom.  I've thought about doing something similar
to your project to monitor fluid levels in tanks.  I can't think of a more economic or easier way.
15  Using Arduino / Sensors / Re: Sensing mechanical alignment on: March 22, 2013, 12:05:18 pm
What are the dimensions of the holes and pin?  Are we talking 0.000" type fit? or 0.030" loose?
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