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46  Using Arduino / Project Guidance / Re: please help with my project since i do not want to fail on: May 15, 2014, 10:50:13 am
by fail i mean fail a high school class

Keep in mind that you are one who may or may not fail as such you should do what others have asked of you instead of ignoring them.  You need to do something to pass the course we do not.

Look up what it means to declare a variable in C, Google is your friend.
47  Using Arduino / Microcontrollers / Re: How To detection of explosives materials ....? on: May 13, 2014, 12:06:53 pm
Governments would monitor this discussion only if they thought they might gain information about explosive detection, they would really like to have better ways of doing explosive detection and would take it from any source and validate on their own.  There is nothing wrong with people researching, building, talking about, ... explosive detection, now if we started to explore defeating the existing technologies they might get concerned. 

Someone who is stupid enough to be discussing nefarious affairs with explosives on an open forum with the readership like this one is very probably too stupid to build a device that would work. 
48  Using Arduino / Project Guidance / Re: How to synchronize many arduinos - shared clock on: May 13, 2014, 09:26:47 am
Probably the most accurate time base you can provide remote Arduinos is using the pulse per second (PPS) option on GPS receivers assuming you have receivers at each Arduino, it is used to re-zero the clock, but the Arduino crystal is still the timer.  Trying to provide resolution of 10-9 sec with a clock that has a crystal with a period of 6.25 x 10-8 sec. is not going to work.

How is the device going to ingest the data from the four Arduinos at the same time without some buffering?  Do you have 4 receivers or does the receiver have a baud rate fast enough to collect 4 messages inside of a couple nanoseconds.

I think you need to explain in detail what you are trying to do and then the incredible body of experience here may be able to help, all we can do without detail is tell you why it won't work not how you achieve your desired result.
49  Using Arduino / Project Guidance / Re: Which flight controller should i use for a fully autonomous Quadcopter ? on: May 11, 2014, 10:09:46 pm
The FAA is the agency to worry about.
50  Community / Gigs and Collaborations / Re: Need help to finish coding Arduino for a Zombie Sensor on: May 08, 2014, 07:34:48 am
The false positive would be indicated if it ever detected a zombie.
51  Using Arduino / Project Guidance / Re: sim card for GPRS shield in USA on: April 21, 2014, 01:32:26 pm
I went with these guys http://www.gprssim.com/index.php?route=common/home
$5/month for 500k and $10 for the SIM card.

$5 per month was what hooked me for development I am not worried about the 500k limit, if I need more I may look around a little bit more.  I just ordered the SIM so I do not have much idea about their service ask me in a bit.

Thanks
wade
52  Using Arduino / Project Guidance / Re: solar tracker problem on: April 19, 2014, 04:23:14 pm
I like the idea of LDRs for tracking the sun. It is wonderfully simple.

I find calculating the positions of the sun easier and less prone to error, the math is not that scary.
53  Using Arduino / Project Guidance / Re: solar tracker problem on: April 19, 2014, 09:39:02 am
The location of the sun in the sky as a function of time and location on the earth has been well known for a very long time.  Instead of "searching" for the sun Google the equations for location of the sun and apply those to your system.

To do this accurately you will need to know the location of the system, a GPS is more than adequate for that and you will have to go through some trigonometry to do the translation.  Keep in mind all trig functions I have ever seen on a computer use radians as the unit for input and output, you will need to convert degrees to radians and back.  Once again use Google if you do not know the conversions.

Hope this helps.
54  Using Arduino / Sensors / Re: Laser Measurement (SF02) Setup & Library on: April 16, 2014, 10:51:54 am
My first thought was to rotate the laser range finder (LRF) in a plane that id parallel to the ground and make measurements of the range as a function of rotation angle to build a low budget LADAR system.  I looked at the data sheet and the max sample rate was 12 Hz so the system would have to rotate very slowly to get a reasonably good picture from the LADAR.  You would not have to rotate the system through the entire circle if you only need it for guidance because you only need to get a picture of where you are going not where you have been, in this case 12 Hz may be fast enough.
55  Using Arduino / Project Guidance / Re: gaining accurate time on time sensitive measurements. on: April 16, 2014, 10:40:34 am
When you say you need accurate timing does that mean the intervals between your 20 Hz times have to be accurate or are do you mean the absolute time of the measurement (day, hour, min, sec) has to accurate?  These are two different issues and need to be addresses separately.

Address the interval timing issue:
You say you want the error/uncertainty small, you should do the analysis to see how small this has to be first and post this metric.  Maybe a standard external crystal will be accurate enough to meet your needs or maybe you need a temperature compensated oscillator or something more accurate.  Without knowledge of how accurate it has to be you can spend a lot of time and money coming up with a result that is two orders of magnitude better than what you needed.  Possibly using the PPS signal from the GPS to zero the timer as a means of reducing drift would be enough.

The absolute timing issue:
In this case I assume you are concerned about making sure your measurements where the time stamps compare very well with the time stamp on measurements collected from another instrument located in a different location.  This case can be helped dramatically by the PPS signal from the GPS, I have used this when making acoustic measurements over an RF networked group of sensors.

Hope this helps,
56  Community / Gigs and Collaborations / Re: Have a great idea. Need technical expertise and development. on: April 12, 2014, 09:28:09 am
PM Sent

Thanks
wade
57  Community / Gigs and Collaborations / Re: Co2 Controller on: April 10, 2014, 08:03:52 pm
Nice Sensor
58  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.
59  Community / Gigs and Collaborations / Re: Paid project - Peltier driver/controller on: March 26, 2014, 12:01:26 pm
Andy,

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

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

Did you get my PM?

wade
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