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Accelerometer adxl335

 
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filjoa



Joined: 04 May 2008
Posts: 260

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Accelerometer adxl335
PostPosted: Mon Mar 01, 2010 3:35 pm     Reply with quote
Hi

I try use this sensor, but it don't work Crying or Very sad

This is my sensor: http://www.sparkfun.com/datasheets/Components/SMD/adxl335.pdf

I connect this sensor direct on ADC ports with 100nf to GND, but on terminal when I run my breadboard I don't have variations on Z and Y only X move little...
Code:

#include <18F252.h>
#device adc=10
#fuses HS,NOWDT,NOPROTECT,NOLVP,BROWNOUT,STVREN
#use delay(clock=20000000)
#use rs232(baud=115200,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)

void main ()
{
 long adc1, adc2, adc3;
 
   setup_adc_ports(AN0_AN1_AN3);
   setup_adc(ADC_CLOCK_INTERNAL);
 
 while (1)
 {
 
 set_adc_channel(0);
 delay_us(10);
 adc1 = read_adc();
 set_adc_channel(1);
 delay_us(10);
 adc2 = read_adc();
 set_adc_channel(2);
 delay_us(10);
 adc3 = read_adc();
 
 printf("Z: %4lu Y: %4lu X: %4lu\r\n",adc1,adc2,adc3);
 delay_ms(100);
 
 }

}


the result:


If I the strange value is on PIN_A2 "X:" but if I change with other values continue wrong on PIN_A2...

Someone can help to find my error?

Best regards
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Mar 01, 2010 3:51 pm     Reply with quote
Quote:

setup_adc_ports(AN0_AN1_AN3);

set_adc_channel(2);

What's wrong in your set_adc_channel() setting ? Can you see it ?
Also, since you're using channels AN0, AN1, and AN3, do you have
the ADXL335 connected to those channels on the PIC ?

Quote:

#include <18F252.h>
#device adc=10
#fuses HS,NOWDT,NOPROTECT,NOLVP,BROWNOUT,STVREN
#use delay(clock=20000000)

setup_adc(ADC_CLOCK_INTERNAL);

Internal RC clock is not recommended for use with the 20 MHz oscillator.
This is the recommended divisor to use: ADC_CLOCK_DIV_32

Also, since this is a Sparkfun product, you should search their forum
for posts on the ADXL335. Like this one about using OpAmp buffers:
http://forum.sparkfun.com/viewtopic.php?p=88789
filjoa



Joined: 04 May 2008
Posts: 260

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PostPosted: Mon Mar 01, 2010 4:39 pm     Reply with quote
Hi

thanks, PCM programmer, I change my conections .. it stay wrong and with your link I solve other problem, I need buffer for this work..

thanks Laughing
filjoa



Joined: 04 May 2008
Posts: 260

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PostPosted: Wed Mar 03, 2010 6:18 am     Reply with quote
Hi

now I have buffers in my ADC ports, but I continue without have correct values, but I start this witch problem stay on my ADC configure...

on datasheet stay write witch this sensor produce 300mV/g, so is my scale goto 0V-5V, I don't have resolution to my sensor correct?

on datasheet tell witch output start on Vcc, how I can start my pwm scale on this value? don't is possible I compare values? how I can use comparate of 18f252?

how I can solve this? I can read ADC direct correct?

best regards
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