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taher
Joined: 12 Mar 2012
Posts: 4
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| Ultrasonic Distance measuring |
 Posted: Mon Mar 12, 2012 7:07 pm |
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Hi everyone,
I am using Ping Ultrasonic sensor and trying to measure the distance of obstacle and I searched for that in the forum before I post that.
So I hope someone can help me.
(sorry for my english not that well)
This is my code:
| Code: |
#include <16F877.h>
#device adc=8
#FUSES NOWDT //No Watch Dog Timer
#FUSES HS //High speed Osc (> 4mhz)
#FUSES NOPUT //No Power Up Timer
#FUSES NOPROTECT //Code not protected from reading
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOCPD //No EE protection
#FUSES NOWRT //Program memory not write protected
#FUSES NODEBUG //No Debug mode for ICD
#use delay(clock=40000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)
#include <LCD.C>
#define trig pin_B1
int16 front_mont,mesure;
int valid=0;
#int_CCP1
void CCP1_isr(void)
{
front_mont=CCP_1;
valid=1;
}
void main()
{
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_spi(SPI_SS_DISABLED);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_INTERNAL|T1_DIV_BY_8);
setup_timer_2(T2_DISABLED,0,1);
setup_ccp1(CCP_CAPTURE_RE);
lcd_init();
enable_interrupts(INT_CCP1);
enable_interrupts(GLOBAL);
// TODO: USER CODE!!
while(true)
{
output_high(trig); // ping the sonar
delay_us(5); // sending 5us pulse
output_low(trig);
if(valid)
{
mesure=front_mont*0.000272;//0.000272=2*10^-7*8*170
valid=0;
}
else
{
set_timer1(0);
}
printf(lcd_putc,"\fDistance=%Lu",mesure);
}
} |
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bkamen
Joined: 07 Jan 2004
Posts: 1615
Location: Central Illinois, USA
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| Re: Ultrasonic Distance measuring |
| Posted: Mon Mar 12, 2012 7:21 pm |
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| taher wrote: | Hi everyone,
I am using Ping Ultrasonic sensor and trying to measure the distance of obstacle and I searched for that in the forum before I post that.
|
Try again.
Use "ultrasonic range"
and you're going to find LOTS of results.
-ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D |
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gpsmikey
Joined: 16 Nov 2010
Posts: 588
Location: Kirkland, WA
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| Posted: Mon Mar 12, 2012 8:42 pm |
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One thing to keep in mind is that most ultrasonic ranging is going to return the closest object (even if that was not what you wanted) - it will see the first echo. That is why I hate digital depth sounders - fish, kelp, thermocline all give false readings of "too shallow". That may not be an issue in your case, but be aware of the problem if it applies.
mikey
_________________
mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3 |
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drh
Joined: 12 Jul 2004
Posts: 192
Location: Hemet, California USA
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| Posted: Tue Mar 13, 2012 8:55 am |
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Another "minor" error. You have specified 40Mhz in the #use delay statement.
This chip has a maximum speed of 20Mhz. Did you intend to use 4Mhz?
_________________
David |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Tue Mar 13, 2012 9:30 am |
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| Quote: |
that most ultrasonic ranging is going to return the closest object
|
is SO true!!
REAL range finder systems use log amps to process multiple return signals of decreasing amplitude pulses and then adds analog differentiation to discriminate within a specified time window to show MULTIPLE returns
not just the closest .
MOST importantly - such designs DO NOT use anything so utterly primitive as a PING sensor either  
i am hearing echoes of a very VERY familiar school project leaking out in this post |
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taher
Joined: 12 Mar 2012
Posts: 4
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| Posted: Tue Mar 13, 2012 6:37 pm |
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thanks for reply
but my ultrasonic sensor send pulse of 40khz that's why i used
"#use delay=40000000" |
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SherpaDoug
Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA
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| Posted: Tue Mar 13, 2012 6:46 pm |
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The PIC processor doesn't care what frequency the ultrasonics run at. That #use delay tells the compiler how fast the PIC is running, ie. what the PIC clock speed is.
_________________
The search for better is endless. Instead simply find very good and get the job done. |
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gpsmikey
Joined: 16 Nov 2010
Posts: 588
Location: Kirkland, WA
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| Posted: Tue Mar 13, 2012 8:01 pm |
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| taher wrote: | thanks for reply
but my ultrasonic sensor send pulse of 40khz that's why i used
"#use delay=40000000" |
Even if that was an issue, 40khz is NOT the same as 40mhz (which is what you specified for the clock). As SherpaDoug points out though, they are not related. It is possible over a limited range to only accept echos within a window along the lines of what asmboy indicated. That is actually a feature that they have started adding to some of the high end camera lenses - you can limit the autofocus range so it can lock faster instead of trying to hunt through the whole range (usually going in the wrong direction first  )
_________________
mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3 |
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