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16  Using Arduino / Project Guidance / Re: closure logger on: June 30, 2014, 02:44:18 pm
For the life of me I can not find the example I am looking for but there are inexpensive linear scales http://www.ebay.com/itm/12-DIGITAL-DRO-TABLE-READOUT-SCALE-for-BRIDGEPORT-/310224430119?pt=BI_Heavy_Equipment_Parts&hash=item483ad12427 that people have written libraries to read them.  The scales provide pretty decent 0.001" accuracy and hold the readings for long periods of time under power.  Sorry I think in inches but 0.001" is about 0.025 millimeters so I believe your requirement is met and I am pretty sure they come in at least 25 cm lengths.

Someone else can probably chime in and direct you to the the code examples to read these scales.

Hope this helps,
17  Using Arduino / Sensors / Re: Material Transparent to Ultrasonic on: June 29, 2014, 01:37:12 pm
Or you could try using special thin latex or rubber that is commonly sold as "something for the weekend"

I imagine one should not go for the french ticklers but just the old plain ones.
18  Using Arduino / Project Guidance / Re: minimal 24h weather forecaster on: June 27, 2014, 08:54:48 am
How about monitoring the output of the panels and using them when the output is above some threshold.  You could buy a smaller solar panel that you monitor in real time for output then you would only turn on the larger array when the smaller one is above some threshold.

wade
19  Using Arduino / Project Guidance / Re: is there any anti jamming arduino module for GPS and GSM modem? on: June 25, 2014, 04:05:43 pm
The best way to help keep a GPS from jamming is to first realize that the GPS signal is below the noise floor and is exploited through coding so any noise in-band will cause problems.  I worked on early small UAVs and we used a lot of ripstop nylon that had EMI shielding on it, we would shield the noise emitters and the GPS module seaprately.

20  Community / Gigs and Collaborations / Re: Help save the Vultures with a 10DOF on: June 17, 2014, 12:08:59 pm
That is a face that even the mother couldn't love.

Even with the above comment I am willing to pitch in on this project.  I am an engineer by training so I try to frame any project early on with the requirements.  I understand that the requirements first route is kind of boring because we all would like to do something because that is exciting and fun, no chance of letting the magic smoke out when you are just working with pencil and paper.  Here are some questions I have after thinking about this project for 5 minutes:
  • Does the egg have to weigh roughly the same as other eggs to spoof the Vulture?
  • Can the egg be replaced if the battery life is a problem, you put the original in why not a second one?
  • Given the real eggs and the fake egg will have different weight distribution the fake will move differently from the real eggs, is this error going to be too high for the study?  One being liquid changing to a bird with structure makes it difficult to make a fake egg close to a real egg.
  • What is the maximum distance allowed between the egg and the RF recorder or repeater?
That sums up my concerns after giving the project a very small amount of thought, if you would like to have me help out leave me a PM.

Thanks
wade
21  Using Arduino / Project Guidance / Re: i need help for my graduation project on: June 16, 2014, 11:55:48 am
I would hate to be the test subject in the wheelchair during the test phase, or for that matter at any time in the life of the chair.
22  Using Arduino / Project Guidance / Re: eye blink sensor on: June 16, 2014, 11:45:17 am
I would urge caution on using an IR LED shining into the eye for long periods of time.  I know most of the IR LEDs you can buy are considered eye safe but I am not sure those thresholds take into account long exposures.
23  Using Arduino / Project Guidance / Re: Tracker Solar on: June 16, 2014, 11:33:29 am
So if you have GPS, you have the time, right?  The clock signal being broadcast by the satellite is atomic-based if I'm not mistaken, and will likely be way more accurate than your RTC.  Each satellite has been calibrated to the same time, and all they do is transmit an ID and the time continuously... I think?   Then the GPS receiver compares the time it took for each of the clock signals to come in and uses some trigonometry to determine your latitude and longitude.  I'm probably oversimplifying, but that's at least how I thought I understood how they work.

I mentioned the RTC as I was just going to use the GPS initially to get the position, enter it by hand and then take the GPS away.  Having an onboard GPS is a great addition.  The price of GPS modules with antenna have come down below $20 so adding a permanent one would not be a big issue.

With the proper equations and evaluation of the math using the GPS time stamp I doubt very much if the search method will beat it.  Also, you need to keep in mind that search/optimization routines can find local mins that many times are not close to the best solution.  I have done a lot of optimizations in a former career and was always anxious if I could not see the results.

wade
24  Using Arduino / Project Guidance / Re: Tracker Solar on: June 15, 2014, 10:57:21 am
There are equations that very accurately estimate the position of the sun based upon the tear, month, day, time and your location, by accurate I think the max error is under 0.5° probably better than a tracker will do.

With these well known equations why not put in an RTC so you know the time, and use a handheld GPS to get the location of the collector (a one time measurement).  Calculate the position of the sun and then just point to the sun, adjust every 5-10 minutes and sleep the rest of the time.  The lag time could be calculated beforee it "went to sleep" by

This method will provide at least as much accuracy and since the system is not always searching for the best situation the driving motors will last longer.
25  Community / Gigs and Collaborations / Re: Gig available: ultrasonic tank level indicator on: June 13, 2014, 07:19:30 pm
LKB,

I sent you a PM.

Thanks
wade
26  Using Arduino / Project Guidance / Re: i need help for my graduation project on: June 12, 2014, 01:59:51 pm
Doing degree completion for money could be disastrous because we would be unleashing completely unqualified engineers on the world and some of them will be designing things that could cause you harm.

With the internet and many documented  cases of plagiarism and cheating in school many students (the OP I am sure does not fall into this category) many engineering students have never been confronted with a problem that a million people have not already done, documented it put it on the web etc.  As I would tell my engineering students no one is going to pay you much money to answer questions that have already been asked.  The hardest problem assigned in your 4 years of class will be easier than a very simple project out in the field.
27  Using Arduino / Sensors / Re: IR reflectance sensor pendulum on: June 11, 2014, 03:40:46 pm
tape a narrow stick on the bottom of the bell and place a photo interrupter so that the stick blocks it as it passes by.

wade
28  Using Arduino / Project Guidance / Re: Help with rebuilding electric golf trolley. on: June 11, 2014, 03:38:00 pm
I personally would use a solid state relay as they have come down in price and controlling that much power is a trivial thing for an SSR as long as you use the spec'ed heat sink.  I may be a little biased but spending a little extra money and getting one a little oversized is a good thing.  It is hard for manufa, ctures to over spec things because they are making 100's, 1000's whatever and want to make as much profit as possible and compete, you are only doing one so you can overbuild it in places.

wade
29  Using Arduino / Project Guidance / Re: Help with Sound Sensor on: June 11, 2014, 08:30:00 am
If you want to amplify sound it will work.  You might want to state what you want to do before asking if it will work.

wade
30  Using Arduino / Project Guidance / Re: Positioning using NRF24L01+ radios? on: June 10, 2014, 09:46:57 am
Quote
If where to place out alot of NRF24L01+ on the racks could I then use a noter NRF24L01+ and arduino on the forks of the forklift to determine on what locator the forks are depending on the streanghts of the sorrunding radios?

Probably not. RF signal strength and distance measurement are really not reliable unless under very ideal conditions.

The advice you are getting is spot on, listen to it.

Maybe the way to do what you want is with RFID tags on the shelves.  The Forklift would have an RFID reader interfaced to an Arduino and the Arduino would be radio linked back to the display you monitor.  This would fail if the sizes of the shelves were too small so the RFID reader got signals from more than one shelf. 

Hope this helps,
wade
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