Author Topic: photodiode vs LDR in line follower (Read 7900 times)

theanxin · « **on:** April 13, 2009, 08:47:03 PM »

What will happen after applied photodiode with infrared on line follower? Is it only move on mirror to reflect the infrared light to the photodiode with black tape? Or its also can works on white paper (like large size of A4 paper) with black tape too?

I know LDR with LED of course can move on both material like above.

theanxin · « **Reply #1 on:** April 13, 2009, 09:12:41 PM »

How to know whether it is photodiode or phototransistor?

SmAsH · « **Reply #2 on:** April 13, 2009, 09:30:13 PM »

uhhh, when you buy it look at what it says?

theanxin · « **Reply #3 on:** April 14, 2009, 08:22:07 AM »

Quote from: SmAsH on April 13, 2009, 09:30:13 PM

uhhh, when you buy it look at what it says?

SmAsH · « **Reply #4 on:** April 14, 2009, 08:22:49 AM »

what about those pretty pictures?

theanxin · « **Reply #5 on:** April 14, 2009, 08:24:02 AM »

Quote from: SmAsH on April 14, 2009, 08:22:49 AM

what about those pretty pictures?

the components looks like i posted above

SmAsH · « **Reply #6 on:** April 14, 2009, 08:25:35 AM »

please explain what you want me to tell you? im not understanding fully? do you want me to tell you what they are?

theanxin · « **Reply #7 on:** April 14, 2009, 08:30:38 AM »

Quote from: SmAsH on April 14, 2009, 08:25:35 AM

please explain what you want me to tell you? im not understanding fully? do you want me to tell you what they are?

I want to know when i applied to the line follower, is it only capable use on mirror to reflect infrared light to the photodiode? how about white paper with black line? But after i tried applied on my line follower microcontrolerless, its seem work on mirror but white paper cant. if want use line follower move on white paper then i should consider use phototransistor? i dont understand about usage of photodiode. i know it able to use as obstacles avoidance and etc.

SmAsH · « **Reply #8 on:** April 14, 2009, 08:33:07 AM »

well think about it, if it works on a mirror but not paper the ir led is not bright enough, there is not enough light to bounce back off the paper as most is getting absorbed. if you can get your hands on a higher brightness one try it with that, or try moving the sonsor closer to the paper. but generally black as a color in general absorbs lots of light.

theanxin · « **Reply #9 on:** April 14, 2009, 08:49:26 AM »

Quote from: SmAsH on April 14, 2009, 08:33:07 AM

well think about it, if it works on a mirror but not paper the ir led is not bright enough, there is not enough light to bounce back off the paper as most is getting absorbed. if you can get your hands on a higher brightness one try it with that, or try moving the sonsor closer to the paper. but generally black as a color in general absorbs lots of light.

hmm.. i did that closer the sensor to the white paper but seems not moving at all. Is it i should not use photodiode with infrared led? but photodiode only receive infrared light but not LED light. maybe photodiode and infrared led only can use on mirror to reflect the infrared light to the photodiode? this questioning my minds. photodiode with infrared works well on mirror. accurate without miss the line.

SmAsH · « **Reply #10 on:** April 14, 2009, 08:51:18 AM »

does it read anything if you have them facing each other? also have you tested the photodiode without having the led turned on as there could be something else effecting it.

paulstreats · « **Reply #11 on:** April 14, 2009, 09:32:41 AM »

since thats just a plain photodiode, I would image that you would first need to run it across a transistor(effectively replicating a phototransistor) and then use a potential divider to output any useable signal. You cant just connect that type of photodiode straight to a microcontroller without doing something with it first

SmAsH · « **Reply #12 on:** April 14, 2009, 01:05:58 PM »

is that to amplify it paul?

msprague · « **Reply #13 on:** April 14, 2009, 01:42:38 PM »

You should be able to use that with paper, not just a mirror.
There are some very good details here:
http://www.societyofrobots.com/schematics_infraredemitdet.shtml

theanxin · « **Reply #14 on:** April 17, 2009, 10:15:10 AM »

Quote from: msprague on April 14, 2009, 01:42:38 PM

You should be able to use that with paper, not just a mirror.
There are some very good details here:
http://www.societyofrobots.com/schematics_infraredemitdet.shtml

do you have video for line follower using photodiode with infrared?

theanxin · « **Reply #15 on:** April 17, 2009, 10:23:13 AM »

Quote from: SmAsH on April 14, 2009, 08:51:18 AM

does it read anything if you have them facing each other? also have you tested the photodiode without having the led turned on as there could be something else effecting it.

same as no respond although photodiode with infrared led facing closely to the white paper and when infrared not turned on if test on white paper. if infrared not turning on then this will cause no infrared light reflect to the photodiode and will cease the dc motor.

theanxin · « **Reply #16 on:** April 17, 2009, 10:27:17 AM »

Quote from: paulstreats on April 14, 2009, 09:32:41 AM

since thats just a plain photodiode, I would image that you would first need to run it across a transistor(effectively replicating a phototransistor) and then use a potential divider to output any useable signal. You cant just connect that type of photodiode straight to a microcontroller without doing something with it first

im not using microcontroller. I using chip called L293D only

theanxin · « **Reply #17 on:** April 17, 2009, 10:30:20 AM »

i ever connect circuit like i posted below but doing this will not give any respon to the mirror or white paper. worst $:-\$ .

theanxin · « **Reply #18 on:** April 17, 2009, 10:38:42 AM »

Because of that, then i connect circuit like i posted below. Amazingly it do give me respon when infrared light reflect to the photodiode when facing on mirror but too bad it cant do it on white paper. $:-\$ . My R1 is 1k while R2 is 10k

theanxin · « **Reply #19 on:** April 17, 2009, 10:47:04 AM »

This circuit i got from PRATHEEK "mysociety of robot website". i built according to this circuit by connecting the Vout sensor to the transistor base.

SmAsH · « **Reply #20 on:** April 17, 2009, 04:47:27 PM »

HEPTUPLE POST! dude, there is no reason to post six times in a row, if you need to add info please use the modify button! i cant understand what you are saying, can you get the sensor to work at all, do you know if your detector is functioning? you may be able to use an amplifier to make the led brighter of use more than one?

Soeren · « **Reply #21 on:** April 18, 2009, 01:30:41 AM »

Hi,

Quote from: theanxin on April 17, 2009, 10:30:20 AM

i ever connect circuit like i posted below but doing this will not give any respon to the mirror or white paper. worst $:-\$ .

That should actually be the easiest circuit for you to get to work, as the important parameters can be set individually.

R1 should be set for a reasonable current through the IR-LED.
R2 should be selected after the amount of ambient light - a trimmer could be used with or without a serially connected resistor.
R3 sets the input impedance and should be equal to the average impedance on the non-inverting input (the parallel value of R2 and the average impedance of the photo transistor in the range of light it will see).
R4 together with R3 sets the gain and like R2 could be made variable to dial in the optimum value.

theanxin · « **Reply #22 on:** April 19, 2009, 11:22:22 AM »

Quote from: Soeren on April 18, 2009, 01:30:41 AM

Hi,

Quote from: theanxin on April 17, 2009, 10:30:20 AM
i ever connect circuit like i posted below but doing this will not give any respon to the mirror or white paper. worst $:-\$ .
That should actually be the easiest circuit for you to get to work, as the important parameters can be set individually.

R1 should be set for a reasonable current through the IR-LED.
R2 should be selected after the amount of ambient light - a trimmer could be used with or without a serially connected resistor.
R3 sets the input impedance and should be equal to the average impedance on the non-inverting input (the parallel value of R2 and the average impedance of the photo transistor in the range of light it will see).
R4 together with R3 sets the gain and like R2 could be made variable to dial in the optimum value.

phototransistor?

? mind to show me the picture of photodiode compare with phototransistor?? how to recognize between photodiode and phototransistor?

Soeren · « **Reply #23 on:** April 19, 2009, 12:40:08 PM »

Hi,

Quote from: theanxin on April 19, 2009, 11:22:22 AM

phototransistor?? mind to show me the picture of photodiode compare with phototransistor?? how to recognize between photodiode and phototransistor?

Photodiode:

Phototransistor:

In short... You can't allways tell the difference by just looking at the physical component.

The schematic you posted had a phototransistor, but a photo diode could be used instead.

theanxin · « **Reply #24 on:** April 19, 2009, 12:59:59 PM »

Quote from: Soeren on April 19, 2009, 12:40:08 PM

Hi,

Quote from: theanxin on April 19, 2009, 11:22:22 AM
phototransistor?? mind to show me the picture of photodiode compare with phototransistor?? how to recognize between photodiode and phototransistor?

Photodiode:

Phototransistor:

In short... You can't allways tell the difference by just looking at the physical component.

The schematic you posted had a phototransistor, but a photo diode could be used instead.

what is the medium use for photodiode and phototransistor

Soeren · « **Reply #25 on:** April 19, 2009, 04:53:58 PM »

Hi,

Quote from: theanxin on April 19, 2009, 12:59:59 PM

what is the medium use for photodiode and phototransistor

I'm not sure what you mean?

(Please cut down what your post don't refer to).

SmAsH · « **Reply #26 on:** April 19, 2009, 05:20:09 PM »

he wants to know what they are generally used for, which i wouldn't have a clue about

theanxin · « **Reply #27 on:** April 20, 2009, 05:54:27 AM »

Quote from: SmAsH on April 19, 2009, 05:20:09 PM

he wants to know what they are generally used for, which i wouldn't have a clue about

ya thats what i meant. i must know more about photodiode compare with LDR after applying on the line follower without microcontroller because i will question by my lecturer about it. That's why i have to get to know more information about its function, features and else after applying on the line follower without microcontroller . BUT Now i still find out why infrared light only reflect on mirror to the photodiode but white paper cant after applying on the line follower without microcontroller. Im sure that i will be question by my lecturer about this.

Soeren · « **Reply #28 on:** April 20, 2009, 10:30:13 AM »

Hi,

Quote from: theanxin on April 20, 2009, 05:54:27 AM

i must know more about photodiode compare with LDR after applying on the line follower without microcontroller because i will question by my lecturer about it. That's why i have to get to know more information about its function, features and else after applying on the line follower without microcontroller .

Ahhh, you want others to do your school work

Quote from: theanxin on April 20, 2009, 05:54:27 AM

BUT Now i still find out why infrared light only reflect on mirror to the photodiode but white paper cant after applying on the line follower without microcontroller. Im sure that i will be question by my lecturer about this.

As I told you... White (or almost any other colour) paper will reflect IR in adequate doses, just reread my post with comments on the components.
You need to first get the bias correct and then adjust the gain of the amplifier to whatever is needed, but remember that ambient light contains lots of IR.

Pause a bit on the questions here and get your hands dirty for a while... That's the only way to get some experience.

Btw. A single modulated IRLED and phototransistor can span a mile or more if used with a lens and/or a parabolic mirror.

theanxin · « **Reply #29 on:** April 21, 2009, 09:30:02 AM »

Quote from: Soeren on April 20, 2009, 10:30:13 AM

Hi,

Quote from: theanxin on April 20, 2009, 05:54:27 AM
i must know more about photodiode compare with LDR after applying on the line follower without microcontroller because i will question by my lecturer about it. That's why i have to get to know more information about its function, features and else after applying on the line follower without microcontroller .
Ahhh, you want others to do your school work

Quote from: theanxin on April 20, 2009, 05:54:27 AM
BUT Now i still find out why infrared light only reflect on mirror to the photodiode but white paper cant after applying on the line follower without microcontroller. Im sure that i will be question by my lecturer about this.
As I told you... White (or almost any other colour) paper will reflect IR in adequate doses, just reread my post with comments on the components.
You need to first get the bias correct and then adjust the gain of the amplifier to whatever is needed, but remember that ambient light contains lots of IR.

Pause a bit on the questions here and get your hands dirty for a while... That's the only way to get some experience.

Btw. A single modulated IRLED and phototransistor can span a mile or more if used with a lens and/or a parabolic mirror.

today im just checking with another groups members that using phototransistor with IR led in their project. I try to use white paper facing on the IR LED and its was reflected to the phototransistor. But photodiode cant.

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Author Topic: photodiode vs LDR in line follower (Read 7900 times)

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