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6406  Using Arduino / Storage / Re: Problems with parallel sram on: July 15, 2011, 07:17:39 pm
Without looking at the code yet, I would remove ALL those caps and put them in the right places. Most of them go from 5v to VCC ! others go from GND to GND, and some are on data and clock lines.

All you need are caps from VCC to GND near each chip.

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Rob
6407  Using Arduino / Microcontrollers / Re: One arduino - 2 baud rate? on: July 15, 2011, 06:53:03 pm
It looks like you have a more or less valid GPS sentence, it's just spread over 20 lines smiley

But where are the dual baud rates? Is this still the deal? What's is "bmp085"?

Can you post all the code?

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Rob


6408  Using Arduino / Programming Questions / Re: array "has not been declared"? on: July 15, 2011, 11:32:02 am
I think it's this line

  int SenseRoutine(int emitter, int counter, byte LEDcathodes[][16], int column)

There was no type so the compiler thought it was a class which of course had not been declared.

Also, AFIAK these are not a valid lines (or if they are I haven't seen that syntax before)

for(int emitter=0, int column=0; emitter<=16, column<=16; emitter++, column++){

SenseRoutine(emitter, 10, LEDcathodes[][16], column);


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Rob
6409  Using Arduino / Project Guidance / Re: Providing short term power to Arduino once main power source is turned off. on: July 15, 2011, 10:51:18 am
Yes I get it, that's why you would need two 12v wires, one switched (for the Arduino) and one not switched (for the LEDs). But if you can't run the extra wire then all bets are off and you're back to supplying 300mA from the backup which is the original problem. 

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Rob
6410  Using Arduino / Project Guidance / Re: Providing short term power to Arduino once main power source is turned off. on: July 15, 2011, 10:34:53 am
@deejayspinz The problem with your drawing is that you are taking the LED power from the "backup power", if you take it from the raw 12v you don't have the huge current draw on the backup.

12V battery
  |->> 12V ign
  |       |->>12V backup pwr (using some circuit [give 5 seconds pwr after car is powered off])
  |       |      |->>>  regulated to 5V for Arduino to power it (and keep it running for 5 secs)
  |->>12V to LEDs (ramp up controlled by arduino via MOSFET and also backed up for 5 secs)

Quote
However, I don't want to have the arduino being powered 24x7 - even though the current draw would be minimal.  I also don't want to source / run a dedicated line for 12V constant
That changes things then, the above does require a second 12v wire.

I think you're right, this is too much trouble for some fading LEDs smiley

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Rob
 
6411  Using Arduino / Project Guidance / Re: Providing short term power to Arduino once main power source is turned off. on: July 15, 2011, 09:54:58 am
Quote
The LEDs will be powered from the 12 source direclty, but the Arduino will use a PWM pin to ramp the LED up from 0 to 255 via a MOSFET.
In that case the current drawn from the cap/battery is just that of the standalone Arduino, well under 10mA I think.

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Rob
6412  Using Arduino / Project Guidance / Re: Providing short term power to Arduino once main power source is turned off. on: July 15, 2011, 08:16:37 am
What if you power the LEDs from the raw 12v, that way they don't need to be powered by the cap. Then you just have to deal with the processor.

Rugged Circuits has an example circuit to do this.  http://ruggedcircuits.com/html/circuit__13.html.

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Rob
6413  Using Arduino / Sensors / Re: Specific gravity sensor, any ideas? on: July 15, 2011, 08:01:37 am
Quote
a potentiometer with (ideally) zero physical resistance,
I doubt such a thing exists.

I tried Googling "Digital hydrometer" and got many results, however most seemed to be very expensive industrial grade or the poster got confused with a "hygrometer" which I think measures humidity.

I gather you're happy to let your existing hydrometer float permanently in the brew, you just want to read it's level.

I do home brew and would like something similar, but no obvious method springs to mind.

Maybe if you confine the hydrometer in a tube that's open to the brew, place a light-weight disc of material on top, then read the distance from the lid with ultra sonic or one of those nifty (Sharp?) range finders.

EDIT: It is Sharp, http://www.acroname.com/robotics/info/articles/sharp/sharp.html#e2

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Rob
6414  Community / Website and Forum / Android/ADK on: July 15, 2011, 07:19:46 am
I know 2/5ths of 5/8ths of naff all about Android and the ADK, but I don't think you have to be clairvoyant to see this will become a big subject on this forum.

When we moved to the new forum we said we'd monitor topics and add/delete as required according to the traffic. Will it be time soon to add an Andriod/ADK root-level topic?

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Rob
6415  Using Arduino / Project Guidance / Re: Mega ADK? Or just a homemade clone for Android based dev. on: July 15, 2011, 07:15:04 am
I'd be inclined to buy a board to start with, but you seem to have a handle on it.

I think subjects about Android/ADK are going to be pretty common in future, maybe it's time for a new top-level topic.

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Rob
 
6416  Using Arduino / Project Guidance / Re: Three voltage measurements + output to a LCD screen on: July 15, 2011, 07:04:03 am
Yes it's very possible, dead simple in fact. In a nutshell the code will be

Serial.print ("Input 1:");
Serial.println (analogRead(pinNumber1));
Serial.print ("Input 2:");
Serial.println (analogRead(pinNumber2));
Serial.print ("Input 3:");
Serial.println (analogRead(pinNumber3));

There will be more but that's the guts of the matter. When you get your hardware and start writing code we can answer more completely.

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Rob
6417  Community / Website and Forum / Re: PinMapping2560 page inaccessible on: July 15, 2011, 07:01:00 am
I get the same. It's either a bad link or not open to the public (can't imagine why and if so the link shouldn't be there in the first place).

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Rob
6418  Using Arduino / LEDs and Multiplexing / Re: sensor array time critical on: July 14, 2011, 07:37:50 pm
I checked out the 2560 data sheet, it only has 3 PC interrupts, thats 24 pins so that won't work either without extra hardware. Personally I think it would work if there was 6 PC interrupts but there ain't so that's that.

I think Mike's IO expander is looking like the best option. The MCP23017 can be configured to interrupt on any change of state on the pins. I don't think it latches the inputs though so you still have to read them as the ball passes but that should be a pretty fast affair.

After that the code logic is as has been described to find the centre, do some trig to get the distance travelled etc.

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Rob
6419  Using Arduino / Project Guidance / Re: More is better: I need LOTS of sensors --> Multiplexer? AD Conversion? on: July 14, 2011, 07:11:39 pm
There are a lot of ADCs around with SPI/I2C interfaces. If you get say 6 octal ADCs you can read 6 inputs at a time to increase the reading speed. So reading 48 inputs is done in the time it takes to read 6 (plus overheads).

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Rob
6420  Using Arduino / LEDs and Multiplexing / Re: sensor array time critical on: July 14, 2011, 10:12:57 am
Quote
Am I correct in understanding that wired "open collector" would mean I can connect all transistors to the same pin without a multiplexer?
That's right, but I just thought of a fault in that idea.

If you connect all the sensor outputs together of course you can no longer read the individual bits. So the ORing has to be done another way, 50/100 diodes and 50/100 resistors, logic gates or whatever. Either way it's getting bigger than Ben Hur.

I reckon it's worth looking at doing it all with a Mega, depending on the pins available you might get 50 that can cause a PC interrupt. If so there's your ORing with no hardware.

The code I posted above can read the ports and you can sort it out later.

It's > 1AM here so I'll sleep on it and look at the Mega schematic and 2560 data sheet tomorrow if nobody has had a better idea before then.

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Rob
 
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