Need help regarding my final year project - Page 2 - Electronic Circuits Projects Diagrams Free

Hayato · 12th November 2006, 01:00 PM

As I said, "Easy comes, easy goes..."

You gave him the complete circuit, but he does not know how to read a schemactic.

Ayne · 12th November 2006, 02:42 PM

Quote:

Originally Posted by abhisinghal2002

thanx a lot dude.....
i think it will solve my prblem a bit.....
can u also provide me the reciever circiut for this.....coz i m tryin to build a speech communcator whc can b used in disaster area's like flood etc..
but still thanx again u've been a gr8 help

It shows that you r in first year, not in final year.

audioguru · 12th November 2006, 03:25 PM

Since the transmitter modulates the light from the laser then its range will be small during the daytime and its receiver's sensistivity pot will need to be turned down to avoid light causing the phototransistor to saturate.

The receiver is an AM detector so it will create loud buzzing at night from street lamps.

It will be extremely difficult to aim the tiny laser beam onto the tiny phototransistor at a distance.

abhisinghal2002 · 13th November 2006, 11:35 AM

Quote:

Originally Posted by crush

from the sounds of it you are working on something similar to the Vic Robot project (victoria university). A friend just developed a laser speech communicator for possible use in Vic Robots in disaster areas.
Put some WORK into it and i can ask him to help u along the way through posts.

u got it rite my freind.....i m on the same project ....disaster communication via laser......can u plz find some thing from ur friend... plz

abhisinghal2002 · 13th November 2006, 11:38 AM

Quote:

Originally Posted by Ayne

It shows that you r in first year, not in final year.

sorry boss

...i read it wrong.....but i must tell u that i m new i the feild of making projects...n i think itz my destination..coz i like them very much...

abhisinghal2002 · 13th November 2006, 11:42 AM

Quote:

Originally Posted by audioguru

Since the transmitter modulates the light from the laser then its range will be small during the daytime and its receiver's sensistivity pot will need to be turned down to avoid light causing the phototransistor to saturate.

The receiver is an AM detector so it will create loud buzzing at night from street lamps.

It will be extremely difficult to aim the tiny laser beam onto the tiny phototransistor at a distance.

yes u r rite but if we modulate the light with high frequency them i think our problem is solved...
n abt the rx. if we make the rx. as a photodetector...thn thr must not be any problem.....wht u

say???????

audioguru · 13th November 2006, 02:13 PM

Quote:

Originally Posted by abhisinghal2002

yes u r rite but if we modulate the light with high frequency them i think our problem is solved...

The laser is Pulse-Position-Modulated with a high frequency. But the receiver is not tuned to the high frequency and doesn't filter out buzzing from street lights. The receiver is too simple, it is just an audio amplifier.

Quote:

if we make the rx. as a photodetector...thn thr must not be any problem...

The receiver already has a photo-transistor as a photo-detector. A photo-transistor saturates when light shines on it. When it is saturated then it doesn't work.

A good system would FM modulate the high frequency of the laser. The receiver would use a photo-diode in the photovoltaic mode which does not saturate. Automatic gain control would control the gain of the amplifier. A tuned circuit would pass the modulated frequency and reject other interfering frequencies. The receiver circuit would have an FM detector to reject amplitude-modulated interference.

The receiver's photo-diode would still need to be shaded from light which would cover-up the modulated signal it receives.

I don't know how you are going to accurately aim the transmitter at the receiver, unless they are permanently installed.

abhisinghal2002 · 13th November 2006, 02:31 PM

Quote:

Originally Posted by audioguru

The laser is Pulse-Position-Modulated with a high frequency. But the receiver is not tuned to the high frequency and doesn't filter out buzzing from street lights. The receiver is too simple, it is just an audio amplifier.

The receiver already has a photo-transistor as a photo-detector. A photo-transistor saturates when light shines on it. When it is saturated then it doesn't work.

A good system would FM modulate the high frequency of the laser. The receiver would use a photo-diode in the photovoltaic mode which does not saturate. Automatic gain control would control the gain of the amplifier. A tuned circuit would pass the modulated frequency and reject other interfering frequencies. The receiver circuit would have an FM detector to reject amplitude-modulated interference.

The receiver's photo-diode would still need to be shaded from light which would cover-up the modulated signal it receives.

I don't know how you are going to accurately aim the transmitter at the receiver, unless they are permanently installed.

thanx a lot for this information....i'll consult it from my project co-ordinatior.....bytheway...wht could be the best solution as per u????

abhisinghal2002 · 13th November 2006, 02:36 PM

Quote:

Originally Posted by Hayato

As I said, "Easy comes, easy goes..."

You gave him the complete circuit, but he does not know how to read a schemactic.

my freind...i m totally new to this field.....but still i want to know abt that......plz dont mind...if u can't help some one...plz don't disheart any one.....

audioguru · 13th November 2006, 02:59 PM

Quote:

Originally Posted by abhisinghal2002

my freind...i m totally new to this field

It is new to me also. I have never seen a laser communicator circuit before.
When I went to school there weren't any lasers and photo-transistors. You should have learned all about this stuff in the school you have been attending for a few years.

You were given a lousy circuit and I have discussed ways to improve it. It still might not work because a modulated light beam is difficult to aim and detect in daylight.
I am shining my laser pointer outside in daylight right now. Even when it shines on something fairly close to me (2m), I can't see it. At night I can see it shine all the way down the street.

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12th November 2006, 01:00 PM	(permalink)
Hayato	As I said, "Easy comes, easy goes..." You gave him the complete circuit, but he does not know how to read a schemactic.

12th November 2006, 03:25 PM	(permalink)
audioguru	Since the transmitter modulates the light from the laser then its range will be small during the daytime and its receiver's sensistivity pot will need to be turned down to avoid light causing the phototransistor to saturate. The receiver is an AM detector so it will create loud buzzing at night from street lamps. It will be extremely difficult to aim the tiny laser beam onto the tiny phototransistor at a distance. __________________ Uncle $crooge