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61  Community / Gigs and Collaborations / Re: Co2 Controller on: April 10, 2014, 08:03:52 pm
Nice Sensor
62  Using Arduino / Project Guidance / Re: long range wireless link to arduino on: March 27, 2014, 09:50:01 am
I think a network of XBee 100 mW 900 MhZ transceivers would work for you.  Set up the network of XBee so that each unit sees the unit behind and in front of it.  The XBees will set up the necessary networking if you have the correct setup so it is a pretty easy solution for low data rate data collection systems.

Small solar cells and batteries could be used to power the intermediate transceivers and to conserve power the radios could be turned on once an hour to broadcast the collected data and then go silent.
63  Community / Gigs and Collaborations / Re: Paid project - Peltier driver/controller on: March 26, 2014, 12:01:26 pm

I have worked up a bid, please check your PM's.

64  Community / Gigs and Collaborations / Re: Paid project - Peltier driver/controller on: March 26, 2014, 08:51:53 am

Did you get my PM?

65  Community / Gigs and Collaborations / Re: Paid project - Peltier driver/controller on: March 25, 2014, 03:34:14 pm
Granted LCD screens can not be used for input I assume that Andy meant to display the parameter value in real time as it is adjusted opposed to blindly setting it and waiting for the system to reach its equilibrium to see what effect your adjustment had on the system.  Add a pot or rotary encoder to set the parameters and the LCD to display the value RT and you are good to go.

A temperature delta of +/-0.2° is tight but is simply a matter of selecting the correct sensors and signal conditioning components and gains on the PID algorithm.
66  Using Arduino / Project Guidance / Re: Function to reverse OPERATIONs of another function on: February 26, 2014, 12:44:13 pm
Functions that undo other functions are called inverse functions.  In standard C that are limited to trig function, exponentials and logs pretty much.

Hope this helps,
67  Community / Gigs and Collaborations / Re: geophysics on: January 19, 2014, 09:23:12 pm
The accuracy usually stated in the GOS specs are the horizontal uncertainties, the vertical uncertainties are much higher.  You can get sub-meter vertical accuracy with additional GPS units and some pretty intense processing, but not with a signal GPS receiver.
68  Community / Gigs and Collaborations / Re: Yet another project: a DAQ on: December 17, 2013, 04:39:53 pm
So, I asked him if I were to make an Arduino alternative. He politely answered, "You will find online software for an oscilloscope and the function generator. Maybe a DMM too. But the spectrum analyzer will be harder and we supply some special instruments written in LabVIEW. Be interesting to see how far you get! By the way, we looked at the Arduino choices early on and none of them had the capabilities and performance we needed."

Can we prove him wrong?

I doubt he will be proven wrong unless someone has the resources to assemble a strong team of hardware and software engineers together, especially given the time restraints.  NI has some amazing software for data acquisition, probably not the best available for a dedicated task but the range of what their software does and the ease it does it is amazing.

I spent a lot of time developing data acquisition software development back when a C compiler fit on a 360k floppy disk and the libraries were on another floppy.  I wish labView would have been available and could have spent the time programming doing Physics, buy alas I was a few processors too early.

Not Much Help,
69  Community / Gigs and Collaborations / Re: Arduino Solar Tracker on: December 17, 2013, 10:50:31 am
Why do people use sensors to track the position of the sun when we know where it is and accurate equations have been developed to calculate the position of it. 

I would recommend google to find the equations that will give you the position of the sun in the sky based on your location on the earth and time of day and point you mirror that direction.  Granted this way you will have to do some geometry work on paper, or similar, but once that is done and verified you are done.  I believe this is a safer, and faster method in addition your part count and circuit complexity drops and this is always a great.  Getting the same thing done with a lower part count is my idea of a very good thing.

One cautionary tip is remember that all of the standard trig functions take the angular argument in radians and also return the angular result in radians, so you will need to convert from the degrees you probably use to radians.  Failure to use the correct angular unit in trig functions will cause you a nightmare or two, I started making that mistake about 35 years ago and seem to make it about every 7 years since.
70  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.

71  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.

72  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.
73  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.
74  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.
75  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?
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