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1  Using Arduino / Project Guidance / Re: How to make the Arduino and RTC work with the Daylight saving time? on: March 10, 2014, 05:37:58 pm
Hi Audrey,
Check out this library by my friend Jack.

https://github.com/JChristensen/Timezone

 It has all the functions you are looking for.  Jack also has libraries for several of the RTC chips used with the arduino on GIT.
Duckie
2  Topics / Science and Measurement / Re: 9 Degree of Freedom on: October 22, 2013, 08:09:58 pm
Hi Baselsw,
do you have any example code or libraries for this sensor?
duckie
3  Using Arduino / Project Guidance / Re: Is it okay to read RTC continuosly? on: September 19, 2013, 04:46:46 pm
I too have several loggers on the net that read the time from the RTC every time through the loop.  I have no issues with accuracy just as others have mentioned.
If you are worried about it, you could use the Time library.  It does a time sync from the RTC periodically rather than every time through the loop.  I also have a couple loggers running in this configuration, with no issues.
4  Using Arduino / Sensors / Re: Glass Broke on: May 05, 2013, 01:59:43 pm
How about a thin trace of conductive ink on the inside surface of the glass?  Then it is a simple reading of an input to monitor the trace for continuity.
5  Using Arduino / Networking, Protocols, and Devices / Re: Serial Communication Trouble on: January 02, 2013, 09:01:38 pm
In the words of your own post and the data sheet:
""To use them to communicate with an external TTL serial device, connect the TX pin to your device's RX pin, the RX to your device's TX pin, and the ground of your Mega to your device's ground."
followed immediately by:
"(Don't connect these pins directly to an RS232 serial port; they operate at +/- 12V and can damage your Arduino board.)"
Do I or don't I connect these pins to the device?"

The first sentence says TTL serial device, not an RS232 device - so no you can't just hook the rx and tx pins to the RS232 device.  It will wreck those pins with the negative voltage.  You need a TTL to RS232 converter chip like the max232 between the pins and the RS232 device.
6  Using Arduino / Project Guidance / Re: How to solder an sd card connector to a pcb? on: December 16, 2012, 11:55:22 am
I have soldered the microSD connectors in a manner similar to SMD components.  Start with a liberal flux application to both the board pads and the connector pads.  Wet one corner pad with solder and then position the connector to the board making sure all the internal pins are aligned to their pads.  Solder an opposite corner pad to secure the connector, and verify if all the internal pads are still aligned.  I then used a 2.5m wide x 0.8mm thick chisel tip inserted through the 'mouth' of the connector laying parallel to the board.  Solder is applied to each pad through the access windows on the top of the connector.  Dont worry about an excess of solder at this point - just make sure you get each and every pad soldered.  Then go back and with a pulling motion drag any excess solder out the front using the soldering iron.  Verify there are no bridges and then solder the other corner pads.  It takes a few to get the hang, but not impossible.
Duckie
7  Using Arduino / Sensors / Re: Arduino UNO and ADXL 345 Accelerometer on: December 09, 2012, 03:07:14 pm
And... don't forget to solder the header pins to the break out board if you want to get meaningful readings.
8  Using Arduino / Networking, Protocols, and Devices / Re: Mistery: I2C not working, blink working on: November 19, 2012, 07:55:48 pm
It may sound too simple, but how are you powering the setup?  I have had I2C issues like this when trying to run from the USB power.  Switch to a real power source and see if it changes your result.
9  Using Arduino / General Electronics / Re: Power Outage Timer on: August 29, 2012, 08:16:27 pm
I am testing one of Jack's RTC boards.  As he indicates, these are really neat RTC chips, with many features.  The power up and power down logging is especially interesting for my data logging arduino's. My board has been running for ~10 days (Jack can correct me on the last time set as he did it before delivery) and I just checked the time against the NPT source.  The error is 7 seconds slow (I have not trimmed it yet -  I want to see the out of the box accuracy).
What you are looking for is included in the library Jack wrote, as an example sketch.
Duck
10  Using Arduino / General Electronics / Re: where to get RJ45-10 cable on: June 23, 2012, 07:20:40 am
My go to place for cables and connectors:  www.monoprice.com
duckie
11  Using Arduino / Networking, Protocols, and Devices / Re: Configuring two Xbee Pro 50mW Serie 2B on: March 23, 2012, 06:46:41 pm
In x-ctu, make sure that you have the 'enable API' clicked and that the 'use escape characters' button is selected.  These are under the PC Settings tab. 
Also in x-ctu, under the modem configuration tab, make sure that AP is set to 2.

Duckie
12  Using Arduino / Project Guidance / Re: What should I get? on: March 19, 2012, 06:16:46 pm
I too am local to that area.  What crazy computer store are you referring to? 
I know of an electronic parts place in St. Clair Shores (11mi and Harper area) called Abel Electronics.
Let Jack and I know if you are in the area and want to meet somewhere?
duckie
13  Using Arduino / Sensors / Re: Help with DHT11 on: March 17, 2012, 05:01:07 pm
If you are looking for dew point and conversions, I use this code:
Code:
// dewPoint function NOAA
// reference: http://wahiduddin.net/calc/density_algorithms.htm
double dewPoint(double celsius, double humidity)
{
  double A0= 373.15/(273.15 + celsius);
  double SUM = -7.90298 * (A0-1);
  SUM += 5.02808 * log10(A0);
  SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
  SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
  SUM += log10(1013.246);
  double VP = pow(10, SUM-3) * humidity;
  double T = log(VP/0.61078);   // temp var
  return (241.88 * T) / (17.558-T);
}

// delta max = 0.6544 wrt dewPoint()
// 5x faster than dewPoint()
// reference: http://en.wikipedia.org/wiki/Dew_point
double dewPointFast(double celsius, double humidity)
{
  double a = 17.271;
  double b = 237.7;
  double temp = (a * celsius) / (b + celsius) + log(humidity/100);
  double Td = (b * temp) / (a - temp);
  return Td;
}

//Celsius to Fahrenheit conversion
float Fahrenheit(float celsius)
{
  return 1.8 * celsius + 32;
}


duckie
14  Using Arduino / Project Guidance / Re: Help with Power Supply problem on: January 30, 2012, 07:13:18 pm
Hi Mitch,
The purity of your power supply would be one of the later things I would look at.

Hardware (wiring) issues or software issues could cause your issue.  Please post your code and we can see what might be going on.
The pullup resistors are needed.  Check the wiring of analog pins 4 and 5  -->  SDA and SCL (respectively)

You mention that the RTC reads all 0's - when the RTC first powers up, it is in a hold state, and it will read all 0's.  You need some code to a) set the time, and b) to start the clock.  Once set and running, the starting code does not need to be rerun.  Check out the playground for the 1307 library and page - and also the Adafruit.com tutorials on the RTC. 

Duckie
15  Using Arduino / Installation & Troubleshooting / Re: high EMI interference (fluorescent lamp) on: January 18, 2012, 08:30:45 pm
I would be concerned about cycling the compressor several times in 5 seconds - not good for life of compressor and it may not even start if cycled that fast.
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