SIDST-GP2

From Curuxa

SIDST-GP2 is a distance sensor with analog output. You can use this module for measuring distance to objects located between 10 to 80cm.

For example, a robot could use SIDST-GP2 to detect obstacles or find objects.

Electronic circuit

Wiring

Bill of materials:

1x Sharp GP2D-12 or GP2Y0A21YK
- Be careful, any other model will not work: GP2D-02, GP2D-15, GP2Y0D21YK...
6x Straight female headers (usually sold as 40-pin strips)
- Note: usually headers are spaced 100mils, but GP2's are closer, you can't use standard 0.1 inch headers
Some thin wire
Some heat shrink tubing

This module doesn't require any kind of homemade electronic circuit. Just buy a GP2D-12 or GP2Y0A21YK and build a simple cable for connecting it to the Main Board.

Printable version: Single, Double, Quad

How it works

SIDST-GP2 will output a voltage level depending on the distance to the closest object put in front of it.

It can be powered from 4.5 to 5.5V, and can measure objects in the 10-80cm range.

The Main Board will receive a given voltage through pin #1 (the data pin). It should be converted using the microcontroller internal Analog-to-Digital Converter.

The distance to the object is inverse to the output voltage, for example:

15cm - 1.65V
25cm - 1.1V
40cm - 0.75V
80cm - 0.4V

All the information and possible output voltages can be found in its datasheet.

Construction

Test

The following code can be compiled using SDCC.

/*==================================================================
* Sample program for SIDST-GP2 using an MBP18
*
* Plug SIDST-GP2 to RA0/AN0 (pin 17) and LTIND-A to RB4 (pin 10).
* The LED will light up when there is an object closer than 25cm
*
* http://curuxa.org
*=================================================================*/
 
#include <MBP18.h>
#include <GP2.h>
 
ConfigBits1(_CP_OFF & _DEBUG_OFF & _WRT_PROTECT_OFF & _CPD_OFF & _LVP_OFF & _BODEN_OFF & _MCLR_OFF & _PWRTE_ON & _WDT_OFF & _INTRC_IO);
 
#define LED RB4
#define LedON 1
#define LedOFF 0
 
void main() {
	TRISB4=0;
	EnableAN0();
 
	while(1) {
		//note: distance and ADC values are inversely correlated
		if(AdcMeasure() > GP2_25cm) LED=LedON;
                else LED=LedOFF;
	}
}

Snippets

/*==================================================================
* Snippet for SIDST-GP2
*
* Using a SIDST-GP2 connected to AN0 and a LTIND-A to RB4.
* The LED will light up when there is an object closer than 25cm
*
* http://curuxa.org
*=================================================================*/
 
#include <pic16fxxx.h>
 
// your config bits here...
 
// insert here code for making A/D conversion (see the snippets category)
 
//digital values for distances when Vcc=5V
//Warning: values and distances are inversely proportional, this means a value bigger than GP2_10cm is actually closer than 10cm
#define GP2_6cm  635
#define GP2_10cm 471
#define GP2_15cm 338
#define GP2_25cm 225
#define GP2_40cm 154
#define GP2_80cm 82
 
#define LED RB4
#define LedON 1
#define LedOFF 0
 
#define bool unsigned int8
#define true 1
#define TRUE 1
 
// Return true if the measured value is closer than a given distance
bool isCloserThan(int measure, int distance) {
    return measure > distance;
}
 
// Return true if the measured value is further away than a given distance
bool isFurtherThan(int measure, int distance) {
    return measure < distance;
}
 
void main() {
	TRISB4=0;
	EnableAN0();
 
	while(1) {
                int adcResult = AdcMeasure();
		if( isCloserThan(adcResult,GP2_25cm) ) LED=LedON;
                else LED=LedOFF;
	}
}

SIDST-GP2 - Curuxa