Pulsed Laser Driver

[nikokapo]

I've noticed that we don't have any pulsed drivers.

Let's say many members like me do not care a lot about burning stuff with lasers but are more interested in beam visibility; would it be possible to create a driver with the same dimensions as a flexdrive (or similar) that pulsed the laser diode? As long as it allows users to drive the diode to higher powers than CW drivers it should be a winner.


What do you think?

 

[lasersbee]

Sure it is possible... I'm testing some pulsed circuits from a member on another forum..
I'm still not finished yet... but doable... They haven't been shrunk down yet..
(weather is too nice to stay cooped up in the shop)...

Jerry

 

[nikokapo]

Sure it is possible... I'm testing some pulsed circuits from a member on another forum..
I'm still not finished yet... but doable... They haven't been shrunk down yet..
(weather is too nice to stay cooped up in the shop)...

Jerry

Awesome. I asked this because I saw that LOC's+Glass lenses were maxed out at around 350mW so I thought "what about pulsing them, could we achieve 500mW?"

Same thing with blurays..imagine a 700mW 8x beam!

 

[Jimmymcjimthejim]

Pulsing drivers are very easy to make. All you need is a 555 circuit hooked up in astable oscillation, and use a transistor to transfer the on/off signal to a driver. I've tried it with a "Groove Driver," and it worked. The only problem is that the transistor will increase the voltage drop by .7V. Oh, and I'm not doing this to push any diodes past limits, I'm doing it to just get a pulsed laser.

 

[nikokapo]

Pulsing drivers are very easy to make. All you need is a 555 circuit hooked up in astable oscillation, and use a transistor to transfer the on/off signal to a driver. I've tried it with a "Groove Driver," and it worked. The only problem is that the transistor will increase the voltage drop by .7V. Oh, and I'm not doing this to push any diodes past limits, I'm doing it to just get a pulsed laser.

lol, but the main idea here is to push the diodes a bit more. Have you tried pushing it?

 

[Jimmymcjimthejim]

No, but I don't see why it wouldn't work. If your transistor and driver can handle the current, then you can push it as far as you want. Today I'm going to test how stable the regulation is at fast pulses. (around 100Hz)

 

[nikokapo]

No, but I don't see why it wouldn't work. If your transistor and driver can handle the current, then you can push it as far as you want. Today I'm going to test how stable the regulation is at fast pulses. (around 100Hz)

I've never seen the specs of a pulsed laser. Last time I worked with a 555 was three years ago
How far do you think a diode could be pushed (I know it depends on the diode, but a rough % estimate to see if it's really worth doing it)?

 

[HIMNL9]

Sorry, but if you want to use a pulsed driver with a LD, the better choice, imho, is using a mosfet, instead a transistor, for the switch part.

lower resistance, practically inexistent drop voltage, much faster and clean switching ..... just as example, something like this one

or, if you prefer it pwm, like this one

also without the components in parallel to the LD, if the circuit is built good enough (no spikes )

 

[nikokapo]

Hmmmmm the PWM looks nice.


Does anybody think this is a good idea or is it just me who wants higher powered beams?

 

[Unreal_JMan]

I definitely think its a good idea Niko, I'd love to have a higher powered beam.
Chuck would be proud.

 

[TheGr8Revealing]

No, but I don't see why it wouldn't work. If your transistor and driver can handle the current, then you can push it as far as you want. Today I'm going to test how stable the regulation is at fast pulses. (around 100Hz)

interesting. how are you test the frequency?

 

[maxh]

Maybe I'm missing something here, but I don't see how driving your LD with pulses will give you a brighter or more powerful beam overall than CW operation. I think people are misinterpreting the LD specs for CW power and pulsed power.

For instance, on the senkat datasheet (http://stonetek.org/shop/SLD1239JL-54.pdf) the CW power rating is 100mw and the pulsed rating is 180mw. It seems that some people are thinking they can get almost a double power beam if they use a pulsed driver, but this isn't the case.

The pulsed rating is the peak power for a single pulse of 30ns, and the duty cycle is 40%. So if you drive your diode at 333MHz with a square wave where each pulse is 180mw and turned on 40% of the time (off the other 60%) then you'll be at the upper limit of your specs, yet your beam will only be, in essence, 72mw (40% of 180mw), rather than the 100mw you can achieve at the upper limit for CW operation. The beam will be dimmer and won't burn matches, etc. as well. Great for burning data on discs, though, since the burning of each bit occurs in just nanoseconds, so 180mw could be considered the average power for that very brief time period.

Am I missing something here?

 

[nikokapo]

Am I missing something here?

Yes. As you see, not every diode behaves the same way, you can clearly verify that with PHR's.
IgorT once stated that LDs could be driven as CW to their PW powers if we used a good driver.

See how 8x's are driven to 400mW...LOC's are driven to +250mW.

30ns is a bit too much in my opinion. At 1000Hz we could achieve a 0,001s period.
I never said anything about burning. Someone already explained that it's the same amount of photons that hit a target so it would be the same deal with PW and CW. But beam visibility plays with our eyes' POV, so if we can pulse the LD to a frequency that is not noticeable (or at least barely noticeable) to the bare eye then we indeed can push them a bit further to make a brighter beam because of short periods of higher peaks of power.

It's the same principle behind pulsing IR LED's to improve the range of remote controls.

 

[Jimmymcjimthejim]

interesting. how are you test the frequency?

It's just an estimate based on the characteristics of the 555 timer.
I used the calculator on this page to get the estimate. It's the third link from the top. "Astable Oscillator Calculator"

Also, guys, I'm not very good with electronics. The reason why I suggested my way, was simply because it works. If anyone has a need to correct me, or make a better suggestion, then go ahead. I'm here to learn

 

[game-genie]

Sorry, but if you want to use a pulsed driver with a LD, the better choice, imho, is using a mosfet, instead a transistor, for the switch part.

lower resistance, practically inexistent drop voltage, much faster and clean switching ..... just as example, something like this one...

...also without the components in parallel to the LD, if the circuit is built good enough (no spikes )

^ACK
I use a mosfet for my airsoft AEG to get a burst of 3 rounds, a single shot or full auto. It works efficient and "clean". But since Airsoft guns arent lasers this comment may be of no use ^^"

Regards
game

 

[FrostyTheDadMan]

Pulsing drivers are very easy to make. All you need is a 555 circuit hooked up in astable oscillation, and use a transistor to transfer the on/off signal to a driver. I've tried it with a "Groove Driver," and it worked. The only problem is that the transistor will increase the voltage drop by .7V. Oh, and I'm not doing this to push any diodes past limits, I'm doing it to just get a pulsed laser.

You are on the correct track but a Lm555 is not fast enough I have found that the LM555 max stable pulse wave is around 1Mhz to 1.25Mhz which is about 100ns depending on the manufacture some only pulse at a rate of 500Khz
and the DVD burning diodes need a PW of 10ns which = 25Mhz to achieve the max pulse power and maintain the life of the Diode.

DSCF5935.jpg picture by FrostyTheDadMan - Photobucket

I have what you are talking about and LaserBee is correct its in testing
I have averaged using a PHR803t running at 150Khz @ 209 mA and have had 244 mA and that's a PHR
Here is a pic of a phr803t running at 209 mA for 58 minutes with out fail but my battery pack lost charge after the 58 minutes past we will be doing a longevity test to see how long the Diode will last.
Its called The Mighty Micro Drive.
DSCF6066.jpg picture by FrostyTheDadMan - Photobucket
When Testing is complete you will be able to get your MMD at LSP Patent Pending #61000221
Read all about it at LE Forum Under The Mighty Micro Drive