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1  Using Arduino / Sensors / Re: Problem with Polulu 3-Axis Accelerometer (MMA7341L) on: May 10, 2013, 12:54:34 pm
I will do this. I don't think its a range issue as the only range options for this chip are 3 and 11 g's. 11's would be waaaay off so i am confidant it is set to 3g mode. As for my math i suppose it could be wrong but i have checked it a ton.
2  Using Arduino / Sensors / Re: Problem with Polulu 3-Axis Accelerometer (MMA7341L) on: May 09, 2013, 07:27:03 pm
I have looked att he speced maximum and minimum V/g and my measurements are still way off. Do you still suggest just calibrating it as it is?
3  Using Arduino / Sensors / Problem with Polulu 3-Axis Accelerometer (MMA7341L) on: May 09, 2013, 06:36:28 pm
I am using the analog pins on my arduino, and have the 3v3 regulator from the accelerometer connected to the aref pin and have set the analog reference to external. I am using the fact that according to the polulu site and the datasheet there is 440mV per g in 3g mode which is what it is set to by default and what i have left it at. I have also measured the 3v3 voltage regulator on the accelerometer with all the outputs connected and measured exactly 3.291V. So in my code I have the calculations go like this: (analogRead() - 511.5) / ((0.44 / 3.291) * 1023)). 0.44 being volts per g, 3.291 being reference voltage and 1023 being the resolution of the ADC. I have the -511.5 because the 0g output voltage is centered between ground (0V) and aref (3.291). This gives me values of -0.02g for y, 0.13g for x and 0.83g for z. This is while the accelerometer is very close to being perfectly flat. Am i doing something wrong or is there something wrong with my accelerometer? Ask me if i left anything out.
4  Using Arduino / Project Guidance / Re: Powering Arduino on 5.5V via USB on: January 19, 2013, 03:39:27 pm
Perfect! thank you very much. I will but a diode in series just in case. got lots of rectifier diodes laying around anyway.
5  Using Arduino / Project Guidance / Powering Arduino on 5.5V via USB on: January 11, 2013, 03:47:11 pm
The ESCs I am using for my quad copter have a 5.5V regulator on them for all the electronics. 5.5V is out of spec (10%) from the USB standard (5%) and I was wondering if it would work, or if it is too much. I can use diodes or something to drop it down if necessary.
6  Using Arduino / General Electronics / Re: Measuring Voltage of Small Lithium Polymer battery, analog errors? on: April 06, 2012, 10:48:09 pm
how would i go about doing this? how would i use the internal 1.1volt reference?
Thanks btw. smiley-grin
7  Using Arduino / General Electronics / Re: Measuring Voltage of Small Lithium Polymer battery, analog errors? on: April 06, 2012, 10:30:12 pm
the readings are spot on now! is there any way of reading the arduino's 5 volt output? and then using that in my calculations?
8  Using Arduino / General Electronics / Re: Measuring Voltage of Small Lithium Polymer battery, analog errors? on: April 06, 2012, 10:28:17 pm
Here's a thought....measure the +5V output of the Arduino.

I bet it's less than 5V smiley

--
The Rugged Circuits Yellowjacket: 802.11 WiFi module with ATmega328P microcontroller, only 1.6" x 1.2", bootloader


yikes! its 4.65! I'm running it of usb. that would explain that. ill try replacing 5 with 4.65 and see if that helps.
9  Using Arduino / General Electronics / Re: Measuring Voltage of Small Lithium Polymer battery, analog errors? on: April 06, 2012, 10:24:10 pm
it reads the analog pin like ~200 times. then every 200 milliseconds takes the average of all those readings and calculates actual volts. Its about 0.3v too high. I'm waiting for the battery to wear down somewhat to see if the 0.3 volts remains consistent. I suspect that it won't.
10  Using Arduino / General Electronics / Re: Measuring Voltage of Small Lithium Polymer battery, analog errors? on: April 06, 2012, 10:08:21 pm
i am doing all those things. The problem is that the arduino is showing a value *higher* than my multimeter.
11  Using Arduino / General Electronics / Re: Measuring Voltage of Small Lithium Polymer battery, analog errors? on: April 06, 2012, 09:57:12 pm
It does work some what because it shows a large voltage drop if i connect a load that draws a fair amount of current from it (small motor). Its just inaccurate.
12  Using Arduino / General Electronics / Re: Measuring Voltage of Small Lithium Polymer battery, analog errors? on: April 06, 2012, 09:37:47 pm
The negative terminal is hooked to ground.
Thanks for the code bit there, I will put that in immediately.
13  Using Arduino / General Electronics / Measuring Voltage of Small Lithium Polymer battery, analog errors? on: April 06, 2012, 09:20:17 pm
So I have a small single cell lithium-polymer battery (3.7 volts nominal) and I am trying to read the voltage level via analog in. measured with my multimeter (10Mohm input impedance) I find the voltage to be 3.8 volts. However using my arduino I find the voltage to be a tad over 4 volts. I am hoping it is the code I am using and not the arduino. The battery is 70mAH.

My Code:
Code:
long batReading = 0;
long numReadings = 0;
long previousMillis = 0;
long interval = 200;

void setup()
{
  Serial.begin(9600);
}
void loop()
{
  unsigned long currentMillis = millis();
 
  batReading = batReading + analogRead(0);
  numReadings = numReadings + 1;
 
  if(currentMillis - previousMillis > interval)
  {
    previousMillis = currentMillis;
   
    double batVolts = 0.0;
    batVolts = batReading / numReadings / 1024.0 * 5.0;
    Serial.println(batVolts);
   
    batReading = 0;
    numReadings = 0;
  }
}
14  Using Arduino / Networking, Protocols, and Devices / Re: Interfacing with Texas Instruments BQ3285EP on: April 05, 2012, 09:31:55 pm
ah ok then. I figured it was, what with the option of intel or motorolla bus speed.
15  Using Arduino / Networking, Protocols, and Devices / Interfacing with Texas Instruments BQ3285EP on: April 03, 2012, 06:49:50 pm
I got one of these RTC's as a sample from Texas Instruments, and I am lost as to how to communicate with it, the datasheet is very confusing: http://www.ti.com/lit/ds/symlink/bq3285e.pdf could anyone shed some light on to how I can go about interfacing with it?
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