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16  Using Arduino / Project Guidance / Re: GPS accurate to microseconds on: November 25, 2013, 11:43:36 am
If the two stations are remote you can use the GPS units to get a time stamp accurate to the accuracy of the system clock as the two recievers will get their pulse per second (PPS) within 10's of nanoseconds.  One way to sync the two units up is to use the PPS line (make sure the GPS unit you are using has a PPS available)  to drive an interrupt on both Arduinos. 

When the PPS interrupt gets triggered you immediately set the system clock to 0 and record the time stamp from the GPS.  Then when you get an interrupt from the zero-crossing detector immediately store the value of the system clock.  When you broadcast the data packet to the central station you send both the time stamp from when the PPS signal was received and the value of the system clock.  It is a good idea to send the timestamp from when the PPS was received in case you missed a PPS signal.

Now think about the "required" microsecond timing accuracy when you are measuring the time difference between 60 Hz signals, I think you are a little overkill.  Whether you need micro or millisecond resolution you still need a way to synch the remote clocks and the PPS from a GPS seems more than adequate for your application.

17  Community / Gigs and Collaborations / Re: Looking for an experienced programmer familiar with Oled displays on: November 12, 2013, 05:53:41 pm
In the past I have programmed quite a few graphic devices but not these, they are interesting enough that I will order 3 to work with and learn the environment given an Adafruit library there should be little problem,

Let me know if you are interested in having me work with you, I have quite a few years of programming experience and do this in my semi-retirement from Lockheed Martin.

18  Using Arduino / Project Guidance / Re: Arduino Due vs Galileo vs. TRE for FFT on Ultrasound on: November 09, 2013, 11:02:54 am
Sounds like a great project for an FPGA, due to its parallel nature.
19  Community / Gigs and Collaborations / Re: programmer/engineer needed on: November 09, 2013, 11:00:36 am
I've sent you a PM about this project.

Same here.
20  Using Arduino / Project Guidance / Re: Cannot find Affordable Precise Milligram Load Cell !! Help!! on: October 05, 2013, 10:38:19 am
Most digital balances with milligram resolution use magnetic restoring force as a sensor instead of strain gages.  I believe this is due to the drift in instrumentation amps.
21  Community / Products and Services / Re: Nokia5110 footprint compatible NEW 128x64 LCD on: September 24, 2013, 04:29:29 pm
Do you ship these to the US?
22  Topics / Science and Measurement / Re: Using an Arduino to process white noise into Random Numbers on: August 20, 2013, 10:20:46 pm
If it is good idea to process white noise to get random numbers it would be widely referenced in statistics literature so maybe you want to start there.  Once you find a algorithm from the statistical experts and scholars you could ask here how to implement them.
23  Using Arduino / Project Guidance / Re: IR Receiver Underwater? on: July 25, 2013, 08:23:29 am
IR gets absorbed by water very rapidly probably within 1,000 wavelengths or so so your comms range would be extremely limited.
24  Using Arduino / Project Guidance / Re: Data logging with Xbee on: July 11, 2013, 08:20:15 am
I have never bought a shield I usually breadboard up what I want to verify it works design a PCB send the files to Osh Park and populate the PCB when I get it back.  Shields work well if you want to stay within the Arduino form factor, at times I find I can greatly reduce the size if I break away from the shields.
25  Using Arduino / Project Guidance / Re: Data logging with Xbee on: July 10, 2013, 07:56:47 pm
You need a MCU on each end and an Xbee to do that, Arduinos can be used easily for this but on the remote unit you are going to need to watch for low power usage and maybe an energy source like solar, depending on how long you want to operate.  The XBee unit on the remote unit would look for a wake up from the unit in your hand and then do a data dump.  You could probably only turn the remote Xbee on say every 30 seconds to listen for the wakeup call.  The usnit in your hand would just have to broadcast its wakeup signal for 30 seconds every time it wants a data dump from the remote XBee.

A few details are probably left out but I think the overall framework would work.
26  Using Arduino / Sensors / Re: Wind speed and direction idea on: July 08, 2013, 09:49:04 am
To get an idea of what the working pressure take your pressure sensors and mount them on the roof of the car on a mast (say 12 inches) and drive it on a calm day and see what how the readings correlate to the speedometer readings.
27  Using Arduino / Sensors / Re: Sensor for stringed instruments on: July 04, 2013, 11:20:29 am
I would use a microphone because unlike a piezo element the mic has a much flatter response as the frequency is varied.  The signal would need to be amplified and then I would run the amplified signal into a comparator the output of the comparator could be fed into a digital input on an Arduino.  The Arduino could measure the time between signals coming and get the frequency and then use a look up table to determine which string got plucked.

This is not as hard as it sounds.  One issue that you will have to watch out for is harmonics of the fundamental freq of the string, the string will not give a pure tone but there will be signals at multiples of the fundamental freq. present.  By setting the threshold correctly on the comparator you will be able to filter out the harmonics.

28  Using Arduino / Project Guidance / Re: Need to shrink and package Arduino Project on: June 30, 2013, 10:29:36 am
To get airspeed you need the difference in pressure between the atmospheric pressure and the dynamic pressure caused by the motion of air into the Pitot tube.  Some applications use one probe with a tube pointing parallel to the center line of the fuselage and one port perpendicular to the first.  The first port gets the dynamic pressure and the second gets the static pressure (atmospheric).  These ports are connected to the 2 ports of your differential pressure sensor to get the differential pressure. 

Hope this helps.
29  Topics / Science and Measurement / Robust Data Logging on: June 23, 2013, 03:36:38 pm
I am logging data onto a PC using serial I/O with the USB cable.  Robust means that when the power cycles the PC will automatically continue to log the data without user intervention.

Does anyone know of a Windows 7 application that would do this?

30  Using Arduino / General Electronics / Re: Chinese Component House Starting w/ Tama??? on: April 22, 2013, 11:48:31 am
That is the one.

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