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46  Using Arduino / Project Guidance / Re: Interfacing with rope leak detector cable? on: July 22, 2014, 08:33:14 pm
Cool. A noob question for you - what all does the change in capacitance mean in this instance versus if it was just changing resistance?

 Most simple sensors work by either changing it's resistance, or capacitance, or induction in presence of a change of the thing being sensed. That in turn determines what kind of circuit it has to interface with.

47  Using Arduino / Project Guidance / Re: Interfacing with rope leak detector cable? on: July 22, 2014, 07:30:32 pm
Well it may have nothing to do with it's resistance, but rather it's change of capacitance in the presence of moisture. The capacitance would then be used to measure a R/C time constant and alarm at a certain value.
48  Using Arduino / LEDs and Multiplexing / Re: starting point for 5x5 RGB LED matrix on: July 22, 2014, 07:25:44 pm

Crossroads' advice will allow you to drive the matrix, you just need 5 npn transistors,  but only with 7 colours. So the next thing to figure out is how to mix more colours using pwm. But you have only 6 pwm outputs. I seem to remember there is a library that emulates more pwm outputs in software...


I am not understanding why I would only get 7 colors.

 Well if you want to count off as a color you have 8 possible combinations, that's all you get with a 3 bit digital selection.
49  Using Arduino / General Electronics / Re: Help understanding transistors on: July 22, 2014, 03:55:39 pm
But what about the 5 volt bit? Surely it would be different spec for one that had minimal resistance at 10 volts.

That will best be handled by using a 'logic level' N-channel MOSFET. They can reach their best Ron spec with just +5vdc gate voltage applied.

50  Using Arduino / Motors, Mechanics, and Power / Re: Minimizing power consumption of an Uno? on: July 22, 2014, 11:47:50 am
What is the base power draw with nothing attached with an empty sketch?

Oh around 40mA or so is a good guess. As others have said it's not a good board for trying for minimum current consumption what with the power on led, usb serial convertor chip, voltage regulator consumption, etc. 
51  Using Arduino / Project Guidance / Re: Interfacing with rope leak detector cable? on: July 21, 2014, 12:30:25 pm
Well if you unit announces a leak by turning on a buzzer alarm you could tape a microphone sensor module to it and use it's output signal as the trigger to an arduino.

52  Using Arduino / Programming Questions / Re: Playing with watchdog and sleep mode - can't upload sketches anymore on: July 20, 2014, 05:45:03 pm
Use Nic Gammon's bootloader program and wiring, it's proven and works fine for the 2560.
53  Using Arduino / Microcontrollers / Re: How to bootload ATmega 328 with arduino UNO as ISP on: July 20, 2014, 01:49:52 pm
Wow, Crossroads, that looks seriously complex! I've always used the method described by ScienceKid with my uno, and never had any problems. This post says it works on uno, you just have to change the delay in the ISP code if you are using Arduino >= 1.0:

Use Nic Gammons sketch and target device wiring as CR posted. It's the simplest fool proof validated method to burn bootloaders to target boards. It also is interactive as you have to open the serial monitor and the sketch tells you what it's doing, when it's doing it and gives other information and of course asks you when to perform the burn.

54  Using Arduino / General Electronics / Re: confusion about Uno schematic and reset-en on: July 20, 2014, 01:36:16 pm
And to further explain the auto-reset 'feature' of the arduino I will add some context. The arduino IDE uses the serial com DTR signal to generate a short pulse that is routed by the signal trace to cause the 328P to reset and start the bootloader which then waits a short time to see if the IDE wants to upload a new sketch, and if not then just runs the sketch that was last loaded into the flash memory. However a side effect of this function is that on most operating systems the opening of a com port (which is what happens when you open the serial monitor) also cause the same board reset that you are seeing, the IDE can't do anything to prevent this behaviour. However as you see the trace art work allows you to 'cut' the signal going to the 328P to stop auto-reset function but then you would not be able to load a sketch unless you either use the reset switch at the correct time when needing to upload a sketch, or install a jumper clip across the cut trace and add the shorting jumper when you wish to upload using auto-reset or remove the jumper when wishing to prevent auto-resets.

55  Using Arduino / LEDs and Multiplexing / Re: starting point for 5x5 RGB LED matrix on: July 20, 2014, 01:18:50 pm
You can control a 5x5 matrix using just 10 output pins. You don't require pwm output pins, your sketch just needs to handle the timing to scan the whole matrix at a rate that prevents 'blinking' display. Generally if you can drive the matrix at a say 20 millisec rate or faster you won't see any indication of scanning, just steady lights.

56  Using Arduino / Programming Questions / Re: How to use TX and RX pins on Arduino Duemilanove on: July 19, 2014, 07:44:47 pm
You DO realize that you can't use the Rx & Tx pins on the UNO as a HOST because they are tied to the USB  via the FTDI chip.
I think you need a second serial port, like Software Serial.

One can use the Rx and Tx pins to send and receive to an external serial device (like another arduino) as long as there is no application on the PC responding to anything sent to it and sending anything back to the arduino. It just gets problematic when one needs to upload a new sketch where usually you have to disconnect the external wiring on the Rx and Tx pins.

57  Using Arduino / Programming Questions / Re: Playing with watchdog and sleep mode - can't upload sketches anymore on: July 19, 2014, 07:33:05 pm
That was a frequent problem with mega boards that had the older version of the bootloader when using the WDT. One can usually get out of the 'lock up' by holding down the reset button and then upload a new sketch and only release the reset button when th e IDE says it's starting the upload. It can take a few attempts to get the timing correct. Long term fix is to burn the latest mega bootloader that can handle WDT correctly.

58  Using Arduino / Programming Questions / Re: When should the float and int variables be put in sketch? on: July 19, 2014, 07:26:06 pm
That is called a "variable's scope" and you should research that topic to get a good feel for the concept as it's an important feature of most modern programming languages.

59  Using Arduino / Microcontrollers / Re: ATMEGA 1284 - Definative Bootloader Solution.... on: July 18, 2014, 05:45:47 pm
Is that even though I dont want to use the bootloader ?
I shall try then...

... and it works !!!


Great. And don't worry about the bootloader being installed, the next time you upload a sketch via ISP the bootloader will be erased but the fuse values will remain.
60  Using Arduino / Project Guidance / Re: Avoiding some transient currents (?) during pin operation on: July 18, 2014, 02:45:49 pm
Not much to work on without your sketch code and schematic drawing. However as a wild ass guess are you using proper debounce functions (either software or hardware) ? Bouncing button contacts can 'fool with' a lot of sketches.

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