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46  Using Arduino / Project Guidance / Re: strange input values in my first helloworld on: February 21, 2014, 01:30:02 pm
Try some smaller resistors and remember that 1) it takes time, albeit a fairly short time, for the ADC caps to charge. that time depends upon the amount of current feeding the analog pins.  you may be sampling before full charge, 2) the value of the resistors change with thier tempreture and thus, supply vayring amounts of current, and 3) you can be picking up some stray volts from surronding electricals and electronics.
47  Using Arduino / Project Guidance / Re: Photosensor activated LED's and Piezo? on: February 21, 2014, 01:22:28 pm
And, one way to gain knowledge is to follow your imagination (until something goes poof...) and another is search and read.

Good luck and have lots of fun.
48  Using Arduino / Project Guidance / Re: Second ATMega chip? on: February 21, 2014, 01:18:56 pm
Then your chip is a Surface mount.  Reread CrossRoads' reply and look up ICSP.  DO NOT attempt to remove the chip. How would you use it in a breadboard setup anyway?
49  Using Arduino / Project Guidance / Re: How to read power measurement with Arduino analog input ? on: February 21, 2014, 01:10:59 pm
I believe the idea is to scale your input voltage to the Arduino analog pin with the voltage divider, such that the input voltage at the analog pin never exceeds the Analog reference which you are using (5V or 3.3V).  The ratio of R2/(R1+R2) gives you the scaling factor (ie: R1= 8K, R2= 2K,  2/10= 1/5= 0.2, so with a maximum of 25V applied to the top of the voltage devider, you would see a max of 5V (25*0.2) at the junction of R1&R2, this applied to Ax would give a value of 1024, using Saravan's 4.883mV, you would calculate 1025*0.004883= 5.000193V, THEN you have to apply the scale factor (0.20) to get back to the actual (approximately) voltage applied to the divider: 5.000193/0.2= 25.00096).  At least I think that's how it works....... fuzzy old fart, forgets a lot of stuff...  

You should also remember that the ADC needs a certain amount of current to charge up the internal caps, so.... you have to limit the total resistance of R1+R2 to keep the conversion time reasonable.  
50  Using Arduino / Project Guidance / Re: Connect 2 or more MPU6050 on board arduino Uno R3 on: February 20, 2014, 11:55:40 am
MPU board 1, tie AD0 to GND (causes board 1 to have an I2C address of 0x68, decimal 104),
                    tie GND to GND of board 1, tie Vcc to Vcc of board 2,
                    tie SCL to XCL of board 2, tie SDA to XDA of board 2,
                    Leave XCL & XDA open, INT depends on whether or not you intend to use it in app.

MPU board 2, tie AD0 to Vcc through a 1k to 10k (your choice) resistor (caused board2 to have an I2C address of 0x69, decimal 105),
                    tie GND to Arduino GND, Vcc to Arduino +5V,
                    tie SCL to Arduino SCL (A4 or A5, don't rember of hand) and through a 4k7 resisror to Arduino +3.3V,
                    tie SDA to Arduino SDA (A5 or A4, don't rember of hand) and through a 4k7 resisror to Arduino +3.3V,
                   INT depends on whether or not you intend to useit in your app.

The stock WIRE lib used A4 & A5 for I2C SCL & SDA. If you want to hook up more than two MPU's, you will need to setup another I2C channel. one way is to initiate another instance of WIRE, using another Analog pin of the Arduino as the SDA for that channel ( and hook up MPU's as above).  Another way suggested is to multiplex the SDA lines with hardware.
This is from memory, but with a little reading, you canget the corrected details. check out the MPU6050 data sheet and the ARDUINO playground.
51  Using Arduino / General Electronics / Re: how to construct this circuit.. on: February 18, 2014, 03:20:59 pm
Why?  I/O9 is only used in one of the two circuits.
52  Using Arduino / Project Guidance / Re: Position Locator on: February 14, 2014, 08:50:48 am
"If it happens to be buried, there will be an impact crater ",,,,  and it will be easy to collect most of the peices.... Not too encouraging a project description.

Says the guy named 1-2-3-Splat smiley-grin

How do you think I got the nickname?
53  Using Arduino / Project Guidance / Re: Creating a 5 dot matrix large scale printer on: February 14, 2014, 08:43:23 am
If it is a fixed message, load the message's character array into eprom and read in a coll at a time, burn move head (or material), read in next coll, burn,,, ans so on.
54  Using Arduino / General Electronics / Re: Arduino to Amplifier to Ultrasonic Transducer on: February 13, 2014, 03:18:43 pm
Google 'NE555 oscillator' or 'NE555 astable' (LM555 is same thing), 'optoisolator' and 'Triac'.
Hazardous project.  Beware of LETHAL currents and voltages (i.e. don't try this at home,,, unless you KNOW what you are doing).
55  Using Arduino / Project Guidance / Re: Arduino cat feeder on: February 13, 2014, 03:10:56 pm
What do you have against fat, happy kitties?
56  Using Arduino / Project Guidance / Re: What to do with your Arduino on: February 13, 2014, 03:08:58 pm
Top of the page, funny color line with Arduino logo.  Below that the words Home, Buy, download, products, learning, reference, support, & blog.  Put your cursor on 'Learning' , left click...
See the words 'Getting Started', put cursor on that and left click.  Start reading there.

I work cheaper than Liudor.
57  Using Arduino / Project Guidance / Re: Arduino cat feeder on: February 13, 2014, 02:54:13 pm
Option four: buy a better cat feeder.
option five:  buy a 50lb. bag of kittles, rip the top open and gently lay it down on the floor.  (Disaster is in the eye of the beholder) Best solution for fat, happy kitties!

Sorry I cannot offer any real help, I can't tell a thing from those pictures.

That said, AA's will give pretty good service, but you'll need 4, or more, to get enough voltage to run arduino and peripherals.  you may want to rething and go with C or D cells.
58  Using Arduino / Project Guidance / Re: Creating a 5 dot matrix large scale printer on: February 13, 2014, 02:42:12 pm
5 by 5 character matrix (not much resolution, but OK) = 5 bit positions (y axis) x 5 time positions (x axis)
with 5 time positions for space (one after each dot) between characters, correct? Example:
      T0   T1   T2  T3    T4  T5   T6   T7   T8   T9
Y3 OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF  = . . . . . . . . . .  ==> .....
Y2 OFF  ON OFF  ON OFF OFF OFF  ON OFF  ON   = . x . x . . . x . x ==> XX.XX
Y1      and so on and so on

If you plan to use lineprinter  style (print a line at a time) move the printhead along the x axis for each print line (Y4 to Y0) and then shift the printed material up or down a line space (space between printed lines). you need a laser print head with 5 lasers and 5 bits in a shift register to represent the drive state of each laser (bit on, laser on,, bit off, laset off).  You shift the bit pattern which represents your T0 (left most) row of your dot matrix for that character, into the shift register. Then latch the shift register, drive the lasers with TTL modulation from the five bits of the shift register, for one second. Save the millis value when you stop the laser drive. move the print head to the T2 position. load the T2 bit pattern into the shift reg. when millis now - millis laser off = 1 second (1000), or better, latch and TTL drive the lasers for T2 pattern.  Assuming that the one second off time is to cool the laser head. With proper design of your laser head, you probablly wont need the one second off after each burn, just add one at the end of each character.

You could simplify your print bed design by printing each Y position simultaneously, but your print head would then have to consist of one laser for each printable bit position in X.  you'll also need a shift reg bit for each printable bit and a buffer in working storage to bild each Y line.  You load the Yx bits into the shifr reg. burn for one sec. shift the printed material up one Y position, latch and burn the next Yx line. and so on and so on.  (not really a good idea, but at great expense in hardware and software resources, gives much faster print time for each message line, and is easier on the lasers).

I may have mis-interpreted your meaning, but I think you should be able to get an idea from the above.
This is NOT the grail of how to do it, just my vision of same.  Good luck!

Depending upon your material and how sensitive it is to the lasers, suggestion 2 is basically how most 'laser' (xerox) printer do it. A print bar out of a dead laser printer may help.  Old IBM 3800 or Xerox 9700 printer systems use heafty IR bars.
59  Using Arduino / Project Guidance / Re: Best product to connect 5 ADXL335 and one MPU-6050 on: February 13, 2014, 01:39:18 pm
While the ADXL345 used I2C, it still only has two I2c base addresses (selectable by hardware) available, and you have a chip select to decide how to handle, so you are still limited to two per channel, or tying up another pin(s) for chip select.  While the MPU6050 is more expensive, it has the same addressability constraints, but offers more data and does most processing requirements on chip.  Makes your job much simpler on the micro-controller side.
60  Using Arduino / Project Guidance / Re: Analog Camera Vision system. on: February 13, 2014, 01:14:50 pm
Why use a camera (for flicker detection? that's a new one to me)?

If your detector is insitu, why not use IR differentiation (unless you don't like the 'it's already been done aspect')?
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