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76  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.
77  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.

wade
78  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.
79  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?

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

Thanks
wade
81  Using Arduino / General Electronics / Chinese Component House Starting w/ Tama??? on: April 22, 2013, 10:30:23 am
A while back someone on this forum pointed me to a component supply house whose name I belive started with Tam.  Does anyone know the source I am referring to.

TIA
wade
82  Community / Products and Services / Re: Square Inch PCB from Electronic Interconnect. on: April 16, 2013, 05:43:55 pm
$3 per square inch is that for 1 or a 100 boards??

I agree that having to create an account to see the prices or post a message here about how good are prices are without a decent disclosure as to what their prices are.  You have heard from any number of people that are not happy to create an account to see your prices.  Claiming to have over 3000 happy customers in response to customers that are not happy with your hidden pricing information is not being very customer friendly.

I do not understand hiding your prices on an instant quote system as any of the competitors could easily use a throw away email account and get your prices easily. 

I am always suspicious at comapanies that are not proud enough of their pricing to advertise up front and out loud, it sounds like I am not the only one.  In today's information age we have all been conditioned to instant gratification in terms of pricing and I think the vendors who realize this will prosper on the bones of those who don't.

wade
83  Using Arduino / General Electronics / Re: altitude detector on: April 05, 2013, 11:08:32 am
If all you want is relative difference in altitude between your location and some other location, say a low-altitude weather balloon, you can use a MPL115A2 on the balloon and one at your location and the difference in atmospheric pressures will tell you the difference in height.  Using the differential pressure method reduces the effects changes in the weather, note I said reduces the effects not eliminates.  After working on systems like this I can tell you the baro method of height estimation will be more accurate then the GPS method in the majority of cases.
84  Using Arduino / Project Guidance / Re: Building a Spring Tester on: March 22, 2013, 09:48:42 am
Have you thought of interfacing to a digital linear scale to make the linear measurements of the spring position?  There are quite a few web pages that discuss interfacing an Arduino to linear scales, I have not checked whether they have the requisite resolution.

To get the required motion you could use a linear actuator rated for the force required and use the arduino interfaced to a motor control board.

Free advice and worth every cent!
85  Using Arduino / Project Guidance / Re: Load sensor amplifier on: March 05, 2013, 12:11:56 pm
I would buy this IC http://www.ebay.com/itm/INA125-Instrumentation-Amplifier-w-precision-voltage-reference-INA125PA-OpAmp-/181049159026?pt=LH_DefaultDomain_0&hash=item2a275eed72
I have used INA125's for load cell amps in the past and this has the benefit of a precision voltage that you can excite the load cell with.

For schematics get the datasheet for the IC and read it.
86  Using Arduino / Sensors / Re: Sound Sensor on: March 02, 2013, 01:53:37 pm
I think you could build a small sensor board that would trigger an alarm based simply upon the volume.  The false alarm rate would probably be very low given that the ambient noise level in the kennel probably rarely gets to a volume close to that of the dog barking.  I do not think you need a noise canceling system given the relative volumes. 

You could set up the sound sensor to light an LED and monitor it to see if you have a false alarm problem so as not to confuse the dogs.  Running just the LED with the sensor would also be required so you could set the threshold at a level to ignore ambient but trigger on barking.  A filter on the sound sensor based on frequency could further reduce the false alarm rate.
87  Using Arduino / Sensors / Re: Self-Levelling with MPU 6050 and 2 servos on: March 02, 2013, 11:55:36 am
Search this site directly or Google the world and you will find places to start and then you can help us by asking direct questions about aspects that you do not understand.  Starting out with the broad type of question like you have will neither help you or us.
88  Using Arduino / Project Guidance / Re: arduino +100Mhz radio jammer on: February 23, 2013, 03:19:11 pm
I am getting great chuckles that anyone over the age of 10 years of age would except what is said on any Wiki page when it comes to laws.  I do not think the I read on Wiki-XYZ would be a very strong defense, at least not strong enough to bet on. 

But hey go for it! You could be setting precedents and if not you may get to meet a bunch of people that you normally don't in your normal walks of life.
89  Community / Products and Services / Re: PCB online service - best price - fast delivery - NO TOOL cost on: February 22, 2013, 11:54:55 am
PCBoards,

It is dangerous to advertise things like the best prices especially in the Google age, I used your online pricing tool to estimate the cost of a small board and it was at least 10 times more expensive than some of favorite vendors like Seeedstudio.com.

Good Luck
90  Using Arduino / Project Guidance / Re: Senior Project (Kickstart) on: February 22, 2013, 11:24:26 am
I worked as the technical director for the Desert Hawk UAV product while at lockheed and one of the difficult problems for small UAVs is an accurate altitude solution.  Actually I should say the height above ground mainly when coming in for a landing, if you have an altitude that is accurate within say 10 feet you can localize your landing much better and reduce damage also from landing.

People have thought of laser range finders but they are a hard nit to crack given the timing and expense of the APD.  Radar is a possibility as is differential baro altimeters, the GPS vertical error is too high to work for this app.  The differential baro would entail putting one of the high accuracy MEMS baro on the bird and one on the groundstation.  The mission time is too long for you to rely on the original baro reading that you took off with so as you approach for landing you send the current baro at ground level in the landing area to the bird.  The height above ground is a simple calculation based on the difference in baro readings, thus the term differential baro. 

Building a small radar altimeter may be a better approach as then you do not need any changes to the ground station and is a little sexier than measuring the air pressure.  The folks over at DIYDrones may help you on test flights if you share some of your completed hardware, trust me that is very cheap flight testing.

wade
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