making a simple amplifier for laser communication project

[glytch]

Hi all,
I saw an article on a website on how to use a pen laser to make a transmitter and receiver so you can transmit sound from a radio or other device line-out via a laser beam across the room.

https://www.scitoys.com/scitoys/scitoys/light/light.html

it didn't involve many components and to my suprise it actually worked!, i could hear my personal stereo from across the room on my computer just by plugging the receiver into the mic jack of my pc and focusing the laser on the cds cell.

Now i see it works, I want to put it all into a nice little box and improve it some more.

What I need is to amplify the signal coming out of the transformer so the laser is brighter to start with as at the moment it is a bit dim running from 3 x 1.5v batteries (I am guessing because of the transformer).

i have looked at simple amplifier circuits but I am a tad confused with how to implement it in the simple circuit for the transmitter. can someone look at the laser transmitter page above and let me know?

thanks!

 

[audioguru]

The Laser is designed to use 4.5V from 3 battery cells. You want to make it brighter? Blow it up?
If you are careful, you could make a regulated power supply with an increased voltage to make-up for the voltage that is lost across the transformer winding. The power supply could use a simple LM317 adjustable-voltage regulator circuit, with a pot you would adjust for exactly 4.5V at the laser.

 

[glytch]

thanks for your reply, I have little idea of what you are saying though :-(
I know what a pot is but unsure about the other, any chance of a diagram?

sorry, I am a bit of a newb and my excitement of putting all these pieces in a see-thru box that actually does something is too much! I'm already thinking of the things I could make with this but my knowledge is lacking :-( I have fiddled with electronics and am very good at putting things like modchips and following instructions but I have never made something to order like this.

thanks in advance
Glytch

 

[audioguru]

If you adjust the voltage too high you will blow-up the laser. Therefore you need a voltmeter.
A power supply will be very simple. Just a 9VDC at about 300mA wall-wart unit, an LM317 adjustable voltage regulator IC (its details are available with a quick search on www.google.com , an output capacitor, two resistors to set the coarse output voltage and a pot that is calculated to match the resistors.

 

[glytch]

thanks! I did some searching and found this..

**broken link removed**

so I am off to the store tomorrow to buy the bits, meanwhile, I'll read up on what value resisitors I'll need...

cheers!

I'll reward you when I've taken over the world with my laser devices. :lol:

 

[bindusar]

i've also made that project but every time my laser blown forever. please give me the power rating of the laser torch u've used.waiting...

 

[bindusar]

Also it may be bcoz of the transformer i am using. Actually i didn't got that specified transformer 8 ohm-1000 ohm. i've made it by myself using a very thin insulated copper wire on air core. may i've any alternative for this transformer such as audioamplifier? waiting...

 

[audioguru]

The laser pointers use the internal resistance of button battery cells to limit their current so they don't blow up. Many laser dides have a max current rating of 50mA.

A transformer with an air core won't work for audio, it might work at an RF frequency.

 

[Sceadwian]

Wouldn't it be possible and a whole lot simpler to just modulate the switch used to turn the laser on and send simple binary? The method described so far is analog and probably very fussy.

 

[audioguru]

Of course you can just turn the laser on and off. But then the voices and music are all chopped up.

The circuit is extremely simple. Bindusar is blowing up his lasers because his power supply doesn't limit the current to the same amount as the button battery cells did. Then he makes an air-core transformer that won't work for audio.

To replace the transformer, all he needs to do is to look in Google for AM Transmitter Modulator Circuit.

 

[bindusar]

i have saw the fluctuations in my laser beam when connected after the transformer, but got the same fluctuations when connected directly to the sound output the radio. we know that a step up transformer increases the voltage but not the power, i.e. it reduces current and a laser beam connected in the output of radio is dependent on the variations in output power of radio. also the beam with and without using trasformer are not giving me those signals when received by LDR even when i am amplifieing the received signal by a power amplifier.
help me as i am living in a rural area and not able to get all necessary items required.

 

[audioguru]

Hi Bindusar,
The receiver circuit that uses a battery cell and an LDR needs a DC load. Connect an adjustable DC load made from a 10k pot like this: