Proximity Distance measurement using IR LED and TR

[banhbao]

ir led distance

Hi, I need to design a fast, not so accurate proximity distance measurement using IR LED and phototransistors. I dont need to measure the exact distance between my robot and the wall. I only need to know whether it's a close, very-close, or far away from the wall. A method that I know is that to adjust the output power of the LED and check to see at what level, the TR response. The output power level at which the reflection becomes undetectable is related to the distance of the object. My question is what is the best way to adjust the power of a LED. Is there a IR detector with built-in oscillator such as the Hamamatsu S3599 so I can adjust the duty cycle of the oscillator? THank you

 

[flatulent]

led distance measurement

One method used is IR tape measurement substitute devices is to modulate the IR emitter with a sine wave superimposed on a DC level. The receiver picks off the sine wave and compares the phase with the transmitted phase. A calibration point is used to compensate for the time delay through the electronics.

 

[xmli1976]

ir sensor tk1838

Hi,I'm very interesting in rangefinger through infrared sensor.But I cann't find detailed information about it on the internet.I just found few commercial products that is expensive.I wish to diy it.

Could you give detailed information about infrared rangefinder or infrared distance measurement.
Such as web site,background theory about infrared rangefinder or books about it,electronic component and schematics.

Thank you very much!

 

[XRimas]

distance measurement using infrared

Why not to use ultrasonic t-r pair. It should be easier. Just search the web.

 

[xmli1976]

tk1838 datasheet

Can Ultrasonic measurement's range be between 10cm to 80cm?
If IR measurement can achieve this,it's better.And I want to
experiment with it.

 

[gecky]

sensor tk1838

I have not tried ultrasound ranging but I have this problem when using IR:

the accuracy of the reading you get is very dependant on the color/surface of the obstacle. Your robot might very well run into a black colored wall! So unless you are operating in a know environment where the obstacles are of a known optical property, IR may not give very ideal results. The phase shift method however, should work but it sounds difficult to implement to me

 

[XRimas]

tk1838

To can overcome dependance on color and partly on surface by using ultrasonic transducers: And yes transducers works in 10-80 cm range.
Check it out: https://www.xilinx.com/bvdocs/appnotes/xapp364.pdf

 

[xmli1976]

infrared distance measurment

I just had wanted to make a rangefinder originally using IR Sensor by pahse shift,but after I have search the web,I found that It's difficult to do it by myself,because it need components such as cdd array and lens.It's difficult for me to acquire them.

 

[gecky]

proximity distance measurement

xmli,

having considered what we all said, I guess you can decide what you want/need based on complexity and cost.

IR method (simple detection of reflected IR and not phase difference) is cheap... The hardware probable cost less than us$5. This of cos excludes any uP that u need....

You can check out the projects ppl do using PICs... quite a bit of info on such ranging stuff!

 

[xmli1976]

t 3 infrared led

Yes,I can decide everything by myself ,because I'm doing everything by myself at home.
As what you have said,simple detection of reflected IR can't be accurate,different color of obstacle reflect different intensity of IR,so that IR sensor generate different voltage values and then distance measured is different.
But if the circumstance is known,you can measure the voltage the sensor generated,so that distance can be measured.Is that right?I havn't saw one using this kind of measurement.Could you tell me a url about this kind of porjects?
The phase shift methor is rarely saw in the internet.I don't know if common IR sensor and led can achieve it.

 

[gecky]

using infrared led

U can try here http://www.winpicprog.co.uk/pic_tutorial_ir_board.htm

Instead of reading the data, I feed the data_out pin of the IR receiver to a cap and ADC the voltage level. The cap has to be discharged before the ADC command is issued. Hope this helps!

 

[xmli1976]

infrared distance measuring circuit

Thank you!
How much voltage can you measure?And how about its accuracy?
Is the theory that the voltage measureed is in proportion to the distance?The more value of voltage,the more distance.

 

[gecky]

distance measurement with ir

Hi,

I do not know the voltage... instead i calibrate my uP in the folling steps:
1. obstacle near - take note of ADC hex value (i display this on my LCD)
2. obstacle far - take note of ADC hex value

3. in the obstacle detection routine, compare the ADC values with those you measured and execute obstacle avoidance rountine if required.

 

[asit]

hamamatsu s3599

Do you know about Sharp IR Rangefinders? They are good, and digital output model is also available. But I dont know about the pricing.

 

[xmli1976]

infrared sensor tk1838

what kind of ADC are you using?Does "uP" stand for uniPorcessoror?
I know Sharp IR Rangefinders,but it's cheaper if I can make one by myself,and it's difficult to find it here.

 

[gecky]

distance measurement using ir

Hi,

uP = micro-processor. In this case, it refers to the PIC i'm using.... PICs are different from the motorolla/atmel uP in the sense that they come with "peripherals"... ADC, USART,comparators etc being a few of them. Visit https://www.microchip.com to find out more.

So, I use a PIC with in-built ADC... 16F877 when i did a school project.

But for a cheaper solution when making my own prject, I use the 16F628 which does not have ADC. Instead. I use "software ADC". U can learn abt this at Nigel's website I listed in my previous reply.

 

[xmli1976]

how to know distant infrared led

I'm using pic uP too.I've apply free samples of 16f877 from microchip.I'm using it in my robot project,such as motor control,IR communcation,ranging.

My IR sensor is tk1838,it seems that this kind of sensor's output have been demodulated,so it cann't be use to measure distance.It receive 38khz of IR frequency,and then generates a low voltage output,if there isn't IR of 38khz frequency,the output is high voltage level.I cann't find exact datasheet of tk1838,but I find that of similar sensor TSOP1838 of Vishay.

how do you achieve the software adc?I cann't find it in Nigel's PIC tutorial.Could you simply describe it?

Thanks!

 

[electron_boy]

speed measurement using infrared

hi,

u can easily construct proximity sensor by an IR pair. all u need are 38khz clk, IR LEDs and a TSOP17xx, xx = 38 u can even substitute a higher freq. construct 38khz clk with 555 and connect it directly to 2 ir leds this will work for 10cm proximity.

tsop1738 is an ir rxr that senses only 38khz signal and forces its o/p to 0v.

bye

 

[gecky]

working of ir sensor as distance measurment

ximli,

look at the circuit for joystick control under Nigel's page. The ADC is explained there.

Yes, the o/p from the IR rx is demodulated already. But there is still a difference in RMS voltage due to the different reflected IR received. So ADC of this value still gives a rough estimate of proximity.

electron_boy's suggestion can be implemented using the PWM module in the PIC to gen the 38KHz sig.

 

[xmli1976]

16f628 infrared emitter c sample

Thanks you very much!
I see.Software ADC is achieve by caculating the time need to charge capacitor to a high voltage level.

hi,

u can easily construct proximity sensor by an IR pair.

Proximity Distance measurement is different with proximity sensor,proximity sensor only sensor obstacle in front of it,but it cann't caculate the distance.