I recently bought a green laser pen which says its 532 nm and power consumption less than 100 mW.

I removed the laser module from the pen and gave it a direct 3.3 Volts power supply from SMPS. It was working perfectly fine.

Then I had to use the same laser module at a distance and the wire runs for about 30 meters. I checked the resistance of that 30 meter wire its about 10 ohms. Now I connected one end of the wire to 3.3 Volts SMPS and connected the other end to the laser module, there is 3.3 volts supply when I meassured but there is no green light coming from laser module. I saw a very dim reddish light around the output lens.

I then removed it and connecred it directly to the power supply, without the 30 meter wire it works perfectly fine.

So why it does not work when the 30 meter wire is coming inbetween the power supply and the laser module. The voltage did not drop through the wire. Is it possible that the 10 ohm wire resistance is affecting the current drawn by the laser module?

What is the possible solution to this. Can I use a constant current buck converter to provide a constant current through it. Please advice a possible solution.

 

there is 3.3 volts supply when I meassured but there is no green light coming from laser module. I saw a very dim reddish light around the output lens.

hi sab,
Those voltage and glow conditions indicate the Laser is not lasing, use a higher gauge 30mtr wire.
Reduce the resistance.
E

 

Or, use a local switcher at the laser.

 

I recently bought a green laser pen which says its 532 nm and power consumption less than 100 mW.

I removed the laser module from the pen and gave it a direct 3.3 Volts power supply from SMPS. It was working perfectly fine.

Then I had to use the same laser module at a distance and the wire runs for about 30 meters. I checked the resistance of that 30 meter wire its about 10 ohms. Now I connected one end of the wire to 3.3 Volts SMPS and connected the other end to the laser module, there is 3.3 volts supply when I meassured but there is no green light coming from laser module. I saw a very dim reddish light around the output lens.

I then removed it and connecred it directly to the power supply, without the 30 meter wire it works perfectly fine.

So why it does not work when the 30 meter wire is coming inbetween the power supply and the laser module. The voltage did not drop through the wire. Is it possible that the 10 ohm wire resistance is affecting the current drawn by the laser module?

What is the possible solution to this. Can I use a constant current buck converter to provide a constant current through it. Please advice a possible solution.

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Whatever you do, always remember DO NOT ever look directly at the light source to "see if its working" that can lead to permanent blindness. Chances are that diode draws around 8 to 11 ohms when operating normally, so adding 10 ohms in series is rather a lot.

Why not just use a relay? put the laser/battery in series with the relay contacts and then use a robust power source to activate the relay at any distance.

 

Measure your 3.3 volts at the source while connected to your laser. Now measure the voltage at the LASER after 30 meters of your leads. Guessing when measuring at the load you won't be close to your 3,3 volts. So I would follow up on Post #2.

Ron

 

Measure your 3.3 volts at the source while connected to your laser. Now measure the voltage at the LASER after 30 meters of your leads. Guessing when measuring at the load you won't be close to your 3,3 volts. So I would follow up on Post #2.

Ron

Yes I didnt meassure the voltage drop on load when the current is being drawn.

I am thinking of measuring the load current, without the 30 meter wire, then with the 30 meter wire use a 5 Volt or 12 volt supply and adding extra resistance in series in addition to the 10 ohms resistance of the wire so that the voltage drop is compensated. The SMPS is a robust one rated for higher amperage so I suppose drawing out current shouldn't be an issue.

 

Yes I didnt meassure the voltage drop on load when the current is being drawn.

I am thinking of measuring the load current, without the 30 meter wire, then with the 30 meter wire use a 5 Volt or 12 volt supply and adding extra resistance in series in addition to the 10 ohms resistance of the wire so that the voltage drop is compensated. The SMPS is a robust one rated for higher amperage so I suppose drawing out current shouldn't be an issue.

My guess, less knowing the current draw is that you are looking at a voltage drop due to your long lead length. Yep, that can be compensated for by supplying a higher voltage at the source or going with a heavier wire gauge as mentioned.

Ron

 

Yes I didnt meassure the voltage drop on load when the current is being drawn.

I am thinking of measuring the load current, without the 30 meter wire, then with the 30 meter wire use a 5 Volt or 12 volt supply and adding extra resistance in series in addition to the 10 ohms resistance of the wire so that the voltage drop is compensated. The SMPS is a robust one rated for higher amperage so I suppose drawing out current shouldn't be an issue.

The downside here is that you'd need to adjust extra resistance if the length of wire ever varied, a relay truly is perfect for this.

 

Question: Is that 30 meter wire for the purpose of using the laser at a different position?? Or for making it "portable"??
Depending on the wire size, that could add a large voltage drop.
A better choice will be to use a power supply with remote sensing! Then you will have the correct voltage at the laser end of the wire.

 

Question: Is that 30 meter wire for the purpose of using the laser at a different position?? Or for making it "portable"??

Its for using the laser at a different position, not for making it portable.

 

Ok I meassured the current without the 30 meter cable at 3.3 Volts it was 315 mA or .315 A.

Then there were 4 wires in the original cable so instead of using two single wires I now used 2 wires as one increasing the gauge. The resistance is now 5.6 ohms and the voltage drop across the wire would be 1.7 Volts. I connected it to a 5 Volt power supply, the voltage drop is compensated and now it is working fine.

The current is .315 A means the power of the laser at 3 Volts is around 1 Watts. But they mentioned it as less than 100 mW which is 0.1 Watts.

 

Hi sab,
Take care when using the laser, as they can permanently damage the eye.
You can purchase goggles to protect your eyes
What is the application use of this laser project?

This link will give you some info on laser diodes.
E

https://pages.rohm.com/Tech_downloa...h-web&gad_source=1&gad_campaignid=23600184378

 

Hi sab,
Take care when using the laser, as they can permanently damage the eye.
You can purchase goggles to protect your eyes
What is the application use of this laser project?

This link will give you some info on laser diodes.
E

https://pages.rohm.com/Tech_downloa...h-web&gad_source=1&gad_campaignid=23600184378

Thanks, I am trying to study the effect of green laser on water.

 

Hi sab,
Check out this link.
E
https://pmc.ncbi.nlm.nih.gov/articles/PMC9824562/