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31  Using Arduino / Programming Questions / Re: First steps debugging on: July 21, 2014, 01:51:50 pm
Debugging on the Arduino is done old school. Judiciously inserted print statements.
32  Using Arduino / Project Guidance / Re: frog detector on: July 17, 2014, 01:05:53 pm
Hook up a garage door opener to run a sweeper across the driveway to sweep the frogs out of the way.
33  Using Arduino / Project Guidance / Re: change the auto-shutdown time on: July 17, 2014, 10:12:18 am
What prevents an auto-shutdown? Is there some innocuous button ("Refresh Display") that you press to keep it going? You might be able to program an arduino to activate a relay every 12 seconds or so to keep it alive.
34  Using Arduino / General Electronics / Re: Why do we need additional resistor between digital input/pushbutton and GND? on: July 17, 2014, 09:50:59 am
You need the resistor because an input on the Arduino that is not connected to anything can "float", and end up at almost any voltage - and randomly read either HIGH or LOW. The resistor "pulls down" the pin to ground to keep it in the LOW state until you push the button to set it at a HIGH state.
35  Using Arduino / General Electronics / Re: Are residential customers billed for Real or Apparent Power ? on: July 17, 2014, 09:22:51 am
Oops, I did not catch the voltage divider effect of the 2.2 uF. I stand corrected.
36  Using Arduino / General Electronics / Re: Are residential customers billed for Real or Apparent Power ? on: July 16, 2014, 11:50:11 am
We are talking about the current draw from the AC line, which is what affects power factor, this is indeed what that current will look like. Current will only be drawn when the AC voltage exceeds the DC voltage, which only happens during the peaks.
37  Using Arduino / Programming Questions / Re: How to extract data from arduino? on: July 16, 2014, 11:05:30 am
You can log to a text file on an SD Card.
38  Using Arduino / General Electronics / Re: Are residential customers billed for Real or Apparent Power ? on: July 16, 2014, 10:12:39 am
Here is an illustration from my Microelectronics text by Millman, to illustrate the point.
39  Using Arduino / General Electronics / Re: Are residential customers billed for Real or Apparent Power ? on: July 16, 2014, 08:16:32 am

Your load here is capacitive, and not very "spiky" at all.  KeithRB has in mind instead, switchmode supplies in which the current is drawn only near the peak of the AC waveform; their power factor is indeed poor but only slightly capacitive; though there are ways of correcting for this in very high power applications using a switching power converter on the input.


No, I am thinking of the circuit he has here. Assuming a DC load on the output, the only time the 1000 uF capacitor is fed current is when the AC Voltage through the rectifier exceeds the DC voltage (+ 2 diode drops!). This causes the AC line to spike the current to recharge the capacitor during the short time of the peak.
40  Using Arduino / General Electronics / Re: Are residential customers billed for Real or Apparent Power ? on: July 15, 2014, 02:56:58 pm
That 1000 uF capacitor will not see AC, anyway, so it will not be reactive power in the usual sense. It will have a sawtooth voltage and very "spiky" current waveform, depending on the load.

Or are you worried about the 225K capacitor?
41  Using Arduino / Programming Questions / Re: Equation giving different results on: July 15, 2014, 11:25:49 am
It is not that double is not a part of the IDE, it is just that floats and doubles are the same size.
42  Using Arduino / Programming Questions / Re: why do we use int instead of long on: July 15, 2014, 08:01:00 am
http://en.wikipedia.org/wiki/36-bit

For computers that had 9 bit 'bytes'

Also crays could only work with 32 bit values, so 8 bit characters were stuffed into the 4 byte word.
43  Using Arduino / Programming Questions / Re: Splitting an integer into its digits - floating point/rounding/conversion error? on: July 14, 2014, 03:12:28 pm
pow is a floating point function. When you cast a floating point number into an int, it does not round, it truncates, so 31.99999999 will become 31.
44  Using Arduino / Programming Questions / Re: why do we use int instead of long on: July 14, 2014, 01:20:55 pm
And even better, assuming you aren't going to change it is
Code:
const byte  ledPin = 13;
45  Using Arduino / Programming Questions / Re: Quick question from a n00b; Can HIGH | LOW be reliably assigned? on: July 10, 2014, 12:57:47 pm
There is much confusion here.
No digital gate will measure a perfect 0 volts. It is guaranteed not to exceed a certain value that will be considered by a logic gate input to be "LOW".

This is a hardware problem.

In the software LOW is a constant value. It is used to set the digital output to the low state, and if a digital input has a voltage lower than the logic '0' threshold is returned to indicate that LOW state.

It will work perfectly fine as a "flag" to indicate that the logic input reads logical '0', even if the voltage on that gate is 0.1 V or so.
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