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826  Using Arduino / General Electronics / Re: FYI: Mounting your PCBS etc. to the inside of an encloser on: March 31, 2014, 08:22:21 am
Enclosure ?
827  Using Arduino / Sensors / Re: How to determine GPS accuracy? on: March 31, 2014, 07:32:04 am
Quote
I've read elsewhere that this is a good GPS chip.  In fact, many RC airplanes/copters/quads use this chip for auto-stabilizing flight.

You've read a lot of rubbish elsewhere,  then.   GPS has no useful function for "auto-stabilising" flight.

If you leave any GPS running with a good view of the sky,   the position will slowly wander around ,  and up and down.   If you are lucky,  about 50% of the time,  that position will be within a 3m circle of your true position,   and the other 50% of the time,  outside it.  The "accuracy" for altitude is much worse.









828  Using Arduino / Sensors / Re: Reading Freescale MPX2202 series pressure sensor on: March 31, 2014, 07:25:14 am
did you notice that this device wants a 10 V power supply ?
829  Using Arduino / Sensors / Re: An idea for wind speed and direction sensing - evaluation please! on: March 31, 2014, 07:13:58 am
It seems to me,  even if you want to bother polling the device often enough to observe the oscillation in rotary speed of the anenometer,   you will have trouble calibrating that oscillation to an actual wind direction.    Particularly as any relationship you determine between the phase of the speed fluctuation,  and the wind direction,  will probably only apply at a particular wind speed,   and will probably vary in an unknown,  non-linear, way.

Determining the actual relationship between a well-balanced anemometer and wind speed is a non-trivial problem,  by deliberately unbalancing the anemometer,  you are making that problem worse.
830  Using Arduino / Sensors / Re: ADXL 345 no reading with SPI on: March 31, 2014, 07:08:21 am
The instructions for chip select are very confusing.  Chip-select = pin 10 is for when you want the arduino to be the spi slave device controlled by something else.    which you usually don't want,   when interfacing with sensors.   Try using a different pin for the chip select signal to the sensor device.
831  Using Arduino / Motors, Mechanics, and Power / Re: Selecting a battery that can handle my current draw on: March 31, 2014, 06:52:54 am
The other solution,  which is not very good,  is that if you get your pump to run from a 9V battery,  well then do it.   And use a separate 9V battery to run the arduino.
832  Using Arduino / Motors, Mechanics, and Power / Re: Selecting a battery that can handle my current draw on: March 31, 2014, 06:49:53 am
Quote
Anyway, I've been shopping around and noticed that maximum current output doesn't seem to be a standard spec for batteries which seems odd to me.

I think you are mistaken about this.   Any battery capable of providing current to drive a motor or other power-consuming device will specific it's current capability.   Perhaps not in an obvious form.   All those C ratings for Lipo and LiFepo batteries are a current rating.  20C  which is typical,  means that the battery can supply all of its available current in three minutes.
833  Using Arduino / Programming Questions / Re: Weird little math problem on: March 31, 2014, 06:42:33 am
Quote
My guess is that this works because the compiler optimises the expression to

Code:

target_rpm = (8 * (potvalue/1000) ) + 1000

Well close,  but no cigar.

8000*potvalue/1000    would optimise to  8*potvalue ,   not to 8*potvalue/1000
834  Using Arduino / Sensors / Re: waterproof sensor dor distance range up to 50 meters on: March 30, 2014, 12:38:03 am
So,   you want this gadget to notice your head,  when you come up for air and you are 20 metres away from it.

That is not a particularly simple problem.

The only way I could see to solve this,   would be to attach some kind of light to your head.   Could be an IR led, or a laser,  or some kind of noisy device.

And then build either a rotating sensor or a conical omnidirectional sensor on the buoy,   which is going to detect the light on your head and steer towards it.   

This seems not impossible ,  but rather complicated and tricky.

If I was going to try this,  I'd start by getting maybe 20 IR photodetector diodes,   and glue them in a circle facing outwards,   and then try steering towards the one which is picking up the signal.       But getting a range more than about 5 metres from them seems to be problematical.

835  Using Arduino / Motors, Mechanics, and Power / Re: turntable: need some advice on motor etc on: March 29, 2014, 10:28:32 pm
You might have a problem with stepper motors being a bit jerky particularly if you are trying to make video.

There is an inherent conflict in designing turntables,  between having enough mass for smooth operation and constant speed,  and having low mass so you can change the speed easily.
836  Using Arduino / Programming Questions / Re: GPS with Arduino UNO. on: March 29, 2014, 10:04:22 pm
You should also consider the possibility that your GPS is not outputting text data at all,  it might be outputting a binary data format.
837  Using Arduino / Programming Questions / Re: EOF --Stop HTML code from being displayed in text file on: March 29, 2014, 09:49:39 pm
You need to be a bit careful when you are talking about an "FF"  character,  because that could mean different things.

There is 0xFF,   which is binary 11111111  ,  equivalent to the integer value -1

and there is 0x0C,   which is binary 00001100,   which is "FF",  the form-feed character,  which is used to advance to the next page in old-style printers,   and has been used with other meanings in various obsolete text file formats.

I read about halfway through this thread before I got confused about which FF  you were talking about.
838  Using Arduino / Programming Questions / Re: Data type troubles on: March 27, 2014, 02:28:58 pm
You are better off shifting your bytes to the correct position,    than trying to do those multiplications.
839  Using Arduino / Programming Questions / Re: Parsing GPS Altitude Data for 16x2 LCD Display on: March 27, 2014, 02:26:59 pm
GPS altitude data is not very reliable.
840  Using Arduino / Programming Questions / Re: Loading a "long" value into eeprom? on: March 27, 2014, 02:23:00 pm
Code:
buf[0] = byte (f1);
buf[1] = byte f1 >> 8;
buf[2] = byte f1 >> 16;
buf[3] = byte f1 >> 24;

What computer language do you suppose this is ?
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