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76  Using Arduino / Sensors / Re: FREESCALE MPL3115A2 PRESSURE SENSOR on: November 09, 2012, 10:17:04 am
Without a schematic and your modified source we are going to have difficulty helping you.
77  Using Arduino / Project Guidance / Re: Project - Arduino to know the difference between 2 objects on: November 09, 2012, 10:05:44 am
If I was looking to do this in volume I would try to find a material that was opaque in the visible yet transparent in the IR and another material that was opaque in the IR and transparent in the visible and arrange matching photodiodes/transistors.  When the objects were brought in they would block the photodiode from its inband light and you could read the values on the PD's to determine what was in front of it.

I say in volume as it may be expensive to set up a run initially for the "water" and "food" objects.
78  Using Arduino / Project Guidance / Re: GPS accurate to cm's? on: November 08, 2012, 04:45:48 pm
You might want to do a SLOC count as a rough metric of whether the processor has enough memory to handle the size of the executable.  I do not have the time to do this and if I were to build a system like this I would port it to a processor that has enough power to do near real time updates.
79  Topics / Science and Measurement / Re: Help with Measuring Load Cell Voltage on: November 04, 2012, 11:29:59 am
For load cells I have good luck with simple instrumentation amps like TI's INA122's powered off the 5 V line from Arduino, the output on it is 0 - 5V.  In your case I would check if you can operate your amp with a lower voltage so your output does not exceed 5 V.  Alternatively, you could probably use a simple voltage divider with two resistors.

80  Topics / Science and Measurement / Re: Help with Measuring Load Cell Voltage on: November 02, 2012, 10:33:15 pm
Listen to Lefty he is making good sense, pat manufactures  and numbers and a schematic would help,
81  Development / Other Hardware Development / Re: Arduino Laser Range Finder on: November 02, 2012, 01:05:33 pm
You may find a pretty good market for these LRFs in the small UAVs to be used for landing aids some of the smaller UAVs land by a controlled crash method as they do not have a reliable idea of how high above the landing surface they are.  A controlled crash from 5 feet is much preferable to one from 50 feet.
82  Using Arduino / Sensors / Re: HELP!.. Does this kind of Transducer Works Underwater? on: November 02, 2012, 12:47:51 pm
That you have made a number of related posts and this kind intrigues me, if you had read that the ultrasonic transceiver worked for your application based on a DIY ROV forum why do you ask here?  It would seem that the ROV forum would have a higher IQ for your ROV application then this forum.

Most of us have been in similar circumstances that you find yourself in and realize we are just going to have purchase the hardware required and try it out on our application and see if it works.  R think you are at that point right now.
83  Using Arduino / Project Guidance / Re: Lone Worker on: October 31, 2012, 02:32:53 pm
I like your idea of the PIR sensor and I think with some logic and a IR tripwire sensor and a magnetic sensor on the door you may be able to have an autonomous system. 

The order in which the tripwire and the door magnetic sensors are triggered could determine whether a person entered the room or left and the PIR sensor could tell you if there was movement in the room.  If there was no movement for a period of time and there was a person in the room an alarm would be triggered.  The benefit of the no movement indicator causing an alarm would give you a better response time if measured between the time someone had an external electrical caused heart attack and when someone brought in some basic life support.  We installed some sensitive PIR in a secure room that would get triggered by mice running on the floor so they can pickup minor motion from a human.

Just some thoughts and I believe there are some holes in the above that can be filled in to create a functional system, but then aagain I may well have missed the boat entirely.
84  Using Arduino / Project Guidance / Re: Guidance on an outdoor surveillance application on: October 31, 2012, 02:20:42 pm
Getting analog signals out that are repeatable and produced by movement is great, what signal off the camera are you reading?  I would think the only signals output would be NTSC or PAL depending upon which side of the Atlantic and to a lesser extent the Pacific you are.

85  Topics / Science and Measurement / Re: Determining accleration due to gravity on: October 31, 2012, 11:54:36 am
Yes I made a huge error I thought for some strange reason the poster wanted to determine the direction of the magnetic field and not the acceleration due to gravity.

I believe with a full-up IMU you could get the direction of the acc. due to g.

86  Topics / Science and Measurement / Re: Determining accleration due to gravity on: October 31, 2012, 10:30:41 am
How about a magnetometer if you only want to measure the direction of the acceleration due to gravity.  I am pretty sure that a magnetometer will not be affected by linear or rotational acceleration.
87  Using Arduino / Sensors / Re: [HELP]Interfacing a Fish Finder's Transducer Sensor on: October 30, 2012, 02:19:12 pm
In air the sensor works from 10-80 cm and you want to get 2 feet ~50 cm through water??

My guess is that if you have the sensor above the water it will tell you the distance to the water, and if you put it underwater as is it short out.

I have stated a couple of times that water greatly attenuates the IR signal but you keep asking about it so I would recommend you buy one of these sensors and try to see performance you get.  The sensors are pretty cheap in the US, can't say for other sources.

I spent a good chunk of my career working many aspects of IR detection and propagation and it would a lot easier for me to buy the sensor and test its performance than try to predict the performance with high accuracy.  But I will say my gut feeling is this sensor will not work for at 2 feet, but you should buy and test its performance and let us know what the performance was in a future email.
88  Topics / Science and Measurement / Re: Determining accleration due to gravity on: October 29, 2012, 10:49:47 pm
Why is the photogate method I described a far easier method of measuring gravity than an accelerometer?

Well there was quite a bit of discussion about using cheap off the shelf accelerometers and I never did see anyone having a solution that actually did measure the acceleration due to gravity, without first assuming what it was to begin with.  By using the photogates you can easily derive the solution for the acceleration due to gravity based on first principles, and not by assuming what the result is you are looking for.  The photogate method is used in first-year physics labs everyday, I used to have my first year students derive the solution for homework, tests, or labs.
89  Using Arduino / Networking, Protocols, and Devices / Re: Wireless sensor network on: October 29, 2012, 04:37:27 pm
What clock source are you using for the time stamping?
90  Using Arduino / Sensors / Re: Long range motion detecting on: October 29, 2012, 04:23:43 pm
Out that far you may have to resort to imaging sensors and use change detection algorithms to detect motion.  Just about anything with images is beyond the capabilities of the 8-bit Arduinos but should work fine on the DUE once all libraries and some more get ported for that processor.  At night with no limited illumination you would probably have to rely on IR imagers, think a lot of money.
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