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46  Using Arduino / Project Guidance / Re: Interrupt triggering unexpectedly on: July 24, 2014, 05:07:35 pm
Simply touching the insulated leads involved in the interrupt can trigger it

That is a typical characteristic of a floating input.
47  Using Arduino / Project Guidance / Re: Trigger an interrupt with an ADC on: July 24, 2014, 05:05:13 pm
ultimatelly the microcontroller will have to react to it and disable the outputs.

I was thinking of something that behaved like a resettable fuse - either self-resetting, or manually resetting. It might be possible to achieve something like that by designing some sort of threshold detector into the output circuit so that the output driver gets pulled to an inactive state when the supply voltage dips, or the supply current rises, or something like that. Alternatively, you might be able to find a smart fuse that does a similar job - I know that this sort of thing is available for 12V DC supplies because they're often used for in-car circuits, but I don't know whether they're available for your voltage / current range and response speed; it would be worth looking, anyway.
48  Using Arduino / Project Guidance / Re: Using LDR as a alert at anytime during program on: July 24, 2014, 04:59:04 pm
Interrupts are best avoided if possible, and when required used only reluctantly and to the minimum extent necessary. I don't think this problem requires interrupts.
49  Using Arduino / Project Guidance / Re: Tech project help on: July 24, 2014, 04:50:23 pm
You need to explain how the 'delay' fits within the sequence you described. To you want it to be a one-off delay when the device is powered up, or are you looking for a start/stop switch?

The code you have currently only seems to drive a couple of outputs which I guess are the step and direction inputs for a stepper driver. If the driver you're using is a shield then you will need to look at the spec for it to understand how many stepper motors it's capable of driving. If it's a separate board then I expect you could add an another couple of motors. The approach you're using in this sketch would be OK as long as you only want to move one stepper at a time and don't need the sketch to control anything else while it is doing that.
50  Using Arduino / Project Guidance / Re: Damaged Arduino, Hard Drive, and USB Hub on: July 24, 2014, 11:38:11 am
It may be that one of your power supplies disagreed about what the ground voltage was, which would result in a short circuit through the ground lkine.
51  Using Arduino / Project Guidance / Re: Video encoding decoding on: July 24, 2014, 11:36:20 am
 The camera will be generating (176 x 144 x 2 bytes for pixel =) 50.688 k bytes

What does that mean in bits per second?
52  Using Arduino / Project Guidance / Re: Storing and sharing your data online on: July 24, 2014, 11:34:07 am
I recommend you start by understanding how the service you want to access is intended to be used (this part does not involve Arduino) and then decide what sort of network interface you're going to give the Arduino. The main options are an Ethernet NIC, a WiFi NIC, or a 3/3G modem.
53  Using Arduino / Project Guidance / Re: Trigger an interrupt with an ADC on: July 24, 2014, 11:30:11 am
Way before the uC has time ...

How quickly do you need to respond to these events?

If a short circuit is reasonably foreseeable then it would be sensible to design the hardware to cope with that rather than rely on a microcontroller to notice and react to it.
54  Using Arduino / Programming Questions / Re: Comparing whole arrays? on: July 23, 2014, 06:07:47 pm
Yes.  They will always be 4 cells.  A user is entering a 4-digit code and this code checks to see (after he enters in 4 digits on a keypad), if he entered in the correct code.

If the array lengths are known and equal, one call to memcmp() will do the job. If you are storing the passwords as null-terminated ascii strings (which would be a reasonable approach IMO) then you could also compare then using strcmp(). If the keypad is only used to enter decimal digits then you also have the option of converting the four digit keypad input sequence to a single integer number which you could then compare directly with ==.
55  Using Arduino / Programming Questions / Re: const int / int on: July 23, 2014, 12:25:01 pm
@KeithRB: AWOL's example is not really using a pointer. A true data item has an lvalue (an address where it lives in memory) and an rvalue (what is contained at that address). Simple assignment statements:

int a = 10;
int b;

b = a;

are rvalue to rvalue exchanges. The same is true in a function call:

That's not quite my understanding. An rvalue is something that can only be the right hand side of an assignment - it is a transient value. For example, (x+1) is an rvalue. An lvalue is something that can be the left hand side of an assignment - it refers to a variable or memory location. I know it's become much more complicated than that but I think the fundamental concepts of lvalue and rvalue are still the same.
56  Using Arduino / Project Guidance / Re: Video encoding decoding on: July 23, 2014, 12:04:41 pm
Since it's unlikely that the LCD would accept a format that exactly matches what the camera module produces, you should expect to do some format conversion between the two. How many bits per second will the camera be generating?
57  Using Arduino / Project Guidance / Re: Average two PWM signals on: July 23, 2014, 12:02:48 pm
   I THINK I want to process the signals which drive the ESC's

Since the Arducopter is generating the signals, it seems to me that the best approach would be to modify the Arducopter sketch to generate the output you want directly.

If you decide to go ahead with an external device instead, I suspect a servo mixer would do the job far better and far cheaper than an Arduino based solution, although an Arduino solution is definitely possible.

Finally, if you take the Arduino approach you would be dealing with a pair of servo control signals, not plain old pwm.
58  Using Arduino / Project Guidance / Re: Need storage advice for tools on: July 22, 2014, 11:23:46 am
I suggest you keep batteries separate from tools and wires etc.
59  Using Arduino / Project Guidance / Re: What is the problem with high frequencies in ADC conversion in Arduino Uno on: July 22, 2014, 09:48:17 am
With the prescaler factor 2, the ADC clock frequency is 8MHz and the sampling rate is 615 KHz. According to Nyquist criteria, the sampling rate should be greater than twice the input frequency. so with the 615 KHz sampling rate, 310 KHz was the maximum input frequency to b processed. But why we are not achiveing  this maximum input frequency signal to be processed. and why the arduino is not allowing to do the conversion(in time credentials), please provide me the proper reason and document.

I never got anywhere near 615 KHz conversion frequency. Even supposing you magically achieved it, and ignoring the fact that the results would be essentially noise, what is your Arduino going to do with each sample in the couple of dozen processor clock cycles it has available?  Bear in mind that just invoking an interrupt handler will probably take more than that. You can sensibly achieve a conversion frequency of a few tens of KHz, but even at that data rate you're going to have to be very careful how you process each sample in order to keep up with the data stream.
60  Using Arduino / Project Guidance / Re: How rugged is Arduino? on: July 21, 2014, 08:15:35 pm
This will be setup outside in a plastic box.

What range of temperature and humidity?
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