Please help in reading digital output of IR sensor

[Mach]

Hi, all.

 

I have successfully used ADC0804 to convert the analogue input of an IR obstacle sensor in to digital form and display the same on an LCD display.

 

My problem is that, the IR sensor that I have also gives me digital output. I want to use this output using Atmel AT89S52 microcontroller and display the same on the LCD display. The sensor gives me analogue output from one pin as well as digital output from another pin. The other two pins the sensor has are 5V Vcc and GND.

 

Please help regarding this as I’m a newbie to the microcontroller world. Thanks in advance.

[AJISH ALFRED]

 

Hi Mach,

 

I understood that you’ve displayed a value on the lcd screen which is the voltage you are getting from the analog pin of your IR sensor. The same can’t be done with your digital pin, as the digital pin basically have only two voltages, one for logic0 and other for logic1.

I’ve little idea about the sensor you are using, please share the part number or a link to the datasheet.

[Mach]

Hi, thank you for your interest. The sensor is an Infrared Obstacle detection sensor with four pins, namely: Vcc(5V), GND, Digital out & Analog out. It can detect obstacles up to 30 cm.

[Mach]

Sorry for my mistake people. I just went through the datasheet got to know that the digital output is of just 1 bit ( a logic 1 or 0)  and NOT 1 byte as in the case of analog output.

My project involves measuring the distance of the obstacle, which I was able to do, but not exactly the result that I wanted.

The thing is that reading becomes high as the obstacle gets nearer to the sensor. But I want the opposite to be happening. That is the reading should become 0(zero) when the obstacle is closest to the sensor and almost 255 (since the analog output is 8-bit)  when the obstacle out-of-range for the sensor.

Any help in solving this is much appreciated in advance.

The datasheet is at this link:- http://probots.co.in/index.php?main_page=product_info&cPath=9&products_id=9

[Amrith]

Hi Mach,

 

Use NOT Gate(74LS04/74HC04) to get your desired result or else simply you can use a transistor(npn).

 

[AJISH ALFRED]

You can use a transistor,

 

Select a npn transistor, BC548

                      

                         _______________________________

       GND<

---

|emitter         base         collector|

---

> 10k resistor

---

> VCC

                         _______________________________

                                               ^                              |

                                                |                               |

                                                |                               |

                                                                                |_____ output to mcu’s adc

                                    resistor >= 10k

 

                                                |

                                                |

                                  your Input from

                                         IR sensor

 

Also you can simulate it in your code, before displaying on the lcd just do it like

255 – value from adc !

[Amrith]

Hi MACH,

Use the below circuit

wysiwyg_imageupload:4844:

[Mach]

Thank you guys for your suggestion. Its working fine now, all because of your suggestions.

[Amrith]

Hi Mach,

You are welcome. Post your qureies & experience further.

[AJISH ALFRED]

 

You are welcome Mach. If you’ve any further doubts, we are here to help you !

[Author]

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