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121  Using Arduino / Project Guidance / Re: Robocup on: October 08, 2012, 10:26:16 am
I will chime in about the IR sensor and maybe that will get the ball rolling.

Is this soccer game going to be outside?  I ask because the IR sensors either photodiodes or transistors will not work outside because the amount of nearIR light in ambient outside light will probably saturate the sensor.  In the event the sensors is not saturated the IR from the ball will probably be far less than that from the sun and the signal may get lost.

You might want to put more thought, or show us that you have thought about, a project if this magnitude before asking us to provide that many general questions.  Google works real good for a lot of general questions and forums for finer points.

122  Using Arduino / Project Guidance / Re: Arduino for Dummies: Using Arduino to turn on light when someone screams on: October 08, 2012, 10:18:11 am
The output from the electret microphone will probably need to be amplified.

123  Using Arduino / Sensors / Re: Accelometer Question on: October 07, 2012, 12:34:41 pm
Remember Google is your friend, I googled 'arduino Wii Nunchuck' and got the following top hits
and closer to home

See if these help,

124  Using Arduino / Sensors / Re: How to obtain values from my 6DOF? on: October 04, 2012, 12:06:10 pm
Have you tried I2C, this is the way it is designed to communicate with other stuff.  Look up I2C on this site and see if you can follow the examples and try it on your sensors. 

You may still have problems as it may be your first attempt at I2C so post back here what your problems are and the sketch that you wrote and then people can give you specific help.
125  Using Arduino / Microcontrollers / Re: Due? on: October 04, 2012, 12:01:13 pm
Maybe it should be called OverDue??
126  Using Arduino / Project Guidance / Re: incorporating GPS in a pan/tilt mount on: October 03, 2012, 08:14:39 pm
The BMP085 you specc'ed has typical error of +/-1hPa which corresponds to almost +/-10 meters of difference in density altitude.   How does the error in density altitude affect your system, the error causes your system to have an error of +/- 10 m so when the calculations are made to calculate the pointing direction of the pan tilt system.  There will also be error in Lat and Lon from the GPS uncertainty so this will cause an error in the pan tilt calculations.

Are these errors too large?  Whether the error will cause problems for you is dependent upon the distance to the objects of interest and the field of view of your camera, to name a few.

127  Using Arduino / Project Guidance / Re: Weather Station / Data Logger on: October 03, 2012, 09:29:18 am
A note on using 2-3 decimal points as an accuracy metric or for that matter any figure of merit.  Assume I make a measurement of a 1.0 centimeter this is 0.00010 kilometers.  The first result has one decimal place and the second has 5, is the measurement any different by only changing the coordinate system?

You need to be a little more quantitative when making requirements on accuracy.

In my research on weather sensors it seems the humidity is hard to measure to within say +/-3% without spending a lot of money and doing occasional instrument calibration.  Buying the equipment for calibration will drive the cost up very quickly.

When starting out on a design of a sensor system making it very accurate is always the initial response.  Somewhere along the design process you need to ask yourself what it is you need to accomplish with the instrument and let that drive your accuracy requirements.  In my first reply I talked about using a humidity sensor that was accurate to +/-5% and saying that was good enough for my application, density altitude measurement.  Humidity's influence on the density is very small so I could get away with a lower quality measurement of it, ther +/-5% error on the humidity did not map over to a +/-5% on the density altitude.

On to sensors, for measuring pressure Freescale was a great line of MEMs sensor and I would encourage you to look at their website.  MEMs sensors was dramatically driven the cost and size of the sensors down and you probably want to exploit that.

128  Using Arduino / Project Guidance / Re: Weather Station / Data Logger on: October 02, 2012, 10:35:28 pm
I have some boards at the fab shop for what I call my Weather Board, it will report air pressure, temperature and rel humidity on I2C.  The overall size of the board is just over a square inch.

Keeping the price of the board down I made some choices of the sensors that may or may not meet your "very accurate" threshold.  The accuracy thresholds may be a problem for relative humidity as the main need for the board was to measure the density altitude and humidity is least significant of the 3 measurements.  You might want to tell us what "very accurate" means so then myself and others know if what have is good enough to help you out.

Being I2C for all the sensors it can easily be used with an Arduino and implemented with GPRS shield.
129  Using Arduino / Microcontrollers / Re: standalone programmer on: October 02, 2012, 08:54:41 am
I use Atmel's AVRISP MkII, it will everything you ask and works well with AVRDude so all you would have to do is write a short batch file and the users could very easily do what you need.  If you need a GUI to do the tasks you could download AVR Studio, Atmel's free IDE.

Here is a link to the MkII

130  Using Arduino / Sensors / Re: The proper way to integrate the MCP9700 temp sensor into an arduino on: September 29, 2012, 06:15:59 pm
Are you using the USB cable to power the Arduino and then the Arduino to power the sensor, if so that may be your problem as the voltage out of the USB can be noisy.  Try using a different method of powering your Arduino like a wallwart DC source of say 9 volts plugged into the DC socket on the board, this may solve your problem.  Alternatively, you could find a USB hub that supplies the 5 V line through its own power supply.


131  Using Arduino / Project Guidance / Re: Altimeter Interfacing on: September 29, 2012, 05:15:21 pm
I misspoke when I said it was only a logger, it also provides altitude data on a serial port here is the description of the serial port settings direct from the manual

"Serial port settings should be configured for 9,600BPS, 8 data bits, no parity, and 1 stop bit. Output data format from the altimeter is ASCII text based, with a <CR> and <LF> character appended to the end of each line."

So you could take the TX port on the logger and wire it to the RX pin on your Arduino and make sure the serial parameters on the Arduino match those stated above and you should be able to read the altitude directly and set thresholds in your sketch to trigger events based upon altitude.

132  Using Arduino / Project Guidance / Re: Altimeter Interfacing on: September 29, 2012, 04:33:54 pm
It does not look like your choice of altimeter allows for direct reading of the altitude as it just logs the data for analysis after the flight.  You could probably hack something if you had the schematics and/or the datasheet on the baro sensor used.

You might be better off starting off with MPXH6101A which measures pressure from 5 to 105 kPa, is 5 kPa low enough?  Although it is surface mounted module I have hon soldered quite a few of these very easily.  Build the basic circuit as shown in the datasheet and either take the output from that circuit directly into the ADC on the arduino.  If the 10-bit ADC does give you enough resolution run it into a separate 12-bit ADC and have arduino read that.

133  Using Arduino / Project Guidance / Re: Arduino + load sensors - sensing people jumping on: September 23, 2012, 11:38:35 am
The load cell you mentioned in principle would work you would probably need multiple cells to get the capacity required.  Most load cells require an instrumentation amp to amplify the signal coming from the wheatstone bridge inside the load cell.  I have had good luck using TI's INA122 for this type of application.  The output from the instrumentation for each load cell would be wired to analog input individually.  To read the total load (weight) you would read all of the load cells convert the voltage read to weight based upon your calibration data, add up all the weights after conversion.

134  Using Arduino / Sensors / Re: How to use RAZOR 9DoF AHRS for positioning on: September 22, 2012, 10:57:51 am
In most circumstances GPS will give you the position of a car much easier than an IMU.  Trying to get your position in an urban canyon with GPS can be difficult because you may not have large enough view of the sky to be able to connect to 4 or more sats, in this instance you may want to try an IMU and update the the position as soon as you get a GPS lock to correct the drift the IMU WILL have.

135  Using Arduino / Project Guidance / Re: PID library multi relay output on: September 20, 2012, 11:37:52 am
No comments on the code.  I wanted to add that solid state relays are great for applications like this.  I have gotten any number of good SSR's from ebay and Criagslist. 

One thing you must do is make sure you have a heatsink on the unit as it does not much inefficiency at 1000 Watts to toast out a solid state device.

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