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1  Using Arduino / Project Guidance / Using 10 photo resistors on: May 02, 2013, 12:28:13 pm
Hi,

I wanted to use 10 photo resistors on one Arduino board, is there a way to multiplex an analog port, or could I use i2c sensors daisy chained?

Thanks,
Nat
2  Using Arduino / General Electronics / Re: Solar Power on: November 21, 2012, 03:31:55 pm
Nope no motors or anything here, Im looking to use a GSM shield, and arduino and a small temp sensor, nothing major or high current by any means. The fucntion i was looking at was a possible way it make sure the battery doesn't over charge or over discharge. I know LiPo's that ive used in R/C Planes are very temperamental about charging and it was something i was worried about with the solar charging being constant.
3  Using Arduino / General Electronics / Solar Power on: November 20, 2012, 12:46:25 am
Hi,

I was wondering if someone could point me towards a good starting point for a solar/battery power solution for an Arduino? I found this: http://www.instructables.com/id/Self-Sufficient-Arduino-Board/?ALLSTEPS but i'm not sure if this would prevent over-charging or dis-charging the batteries. I'm a new Computer Engineering/Electrical Eng student so the goal here is to learn how/why/what I should do. So any help by some more experienced guys would be awesome!  smiley

I also found this online and seems to be like a good little function:

Code:
float read_battery(void) { // Honk, 14 - 11 - 10 (function was totally missing in NG trunk)
  /*Circuit:
   
    Vin--D1--R1--|--R2--GND
                 |
                 |
                Vout
  */
  //If lipo is 12.6V and diode drop is 0.6V (res 12.0V), the voltage from divider network will be = 2.977V
  //calculation: AREF/1024.0 is Vout of divider network
  //Vin = lipo voltage minus the diode drop
  //Vout = (Vin*R2) * (R1+R2)
  //Vin = (Vout * (R1+R2))/R2
  //Vin = ((((AREF/1024.0)*adDECIMAL) * (R1+R2)) / R2) + Diode drop //(aref/1024)*adDecimal is Vout
  #define R1 10050 //the smd 10k from battery
  #define R2 3260 //the div resistor user put in (3k3 makes for about 13.5V before hitting AREF 3.3V)
  #define AREF 3.3F //we have used analogReference(EXTERNAL)
  #define DIODE_FWD_VOLTAGE_DROP 0.6F //measure with DMM across D1 (input diode in series with Vin)
 
  float batteryVoltage = (((analogRead(VDIV1)*(AREF/1024.0)) * (R1+R2)) / R2) + DIODE_FWD_VOLTAGE_DROP;
  return(batteryVoltage); 
}

Thanks,
Nat
4  Using Arduino / Project Guidance / Re: Multiple I2C, shields, and Uno Board on: August 27, 2012, 12:15:14 pm
Ah, so like this?


A4------4.7K pullup resistor-----RTC-------lcd+buttons
                                                                                           
A5------4.7K pullup resistor-----RTC-------lcd+buttons
5  Using Arduino / Project Guidance / Re: Multiple I2C, shields, and Uno Board on: August 27, 2012, 12:00:49 pm
yes, the wave shild does not use I2C so that will be in the digital pins as needed.

the other two divices do use I2C though so to wire them it should look like this:


A4------4.7K pullup resistor-----RTC----4.7K pullup resistor-------lcd+buttons
                                                                                           
A5------4.7K pullup resistor-----RTC----4.7K pullup resistor-------lcd+buttons

(the ------ is the connections, wire)

is this the correct way to wire the pins?

6  Using Arduino / Project Guidance / Multiple I2C, shields, and Uno Board on: August 27, 2012, 10:18:21 am
Hi,

I have picked up a few shields that i need for a project from adafruit:

https://www.adafruit.com/products/255
https://www.adafruit.com/products/94
https://www.adafruit.com/products/714

For a project for much I need to play a sound file on each hour. I had a question about how the pins should be wired here is what each item needs:

RTC
    VCC, GND, SDA, SCL
LCD + buttons
    VCC, GND, SDA, SCL
Wave Shield
    Pins 13, 12, 11, 10, 2, 3, 4 and 5

so the wave shield should be wired to those pins as needed, for the RTC and lcd+ buttons, should i wire both to the SDA (Analog 4) and SCL (Analog 5)? I know they are both I2C interfaces but i wasnt sure if i should just use a Y in the wire and put both in the one pin out on the board.

Nat
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