Using a DC/DC converter to power the laser

Still, if i do get my second sample order on my company, i'd have enough, to send some to Phenol, if he can't order them himself...

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thanks for your willingness. I will try to place another order and see their reaction.
regarding filter chokes, IgorT, you could also use those axial coils you already have. just make sure they can handle the current, as there are some quite tiny types rated for <100mA

phenol said:

thanks for your willingness. I will try to place another order and see their reaction.
regarding filter chokes, IgorT, you could also use those axial coils you already have. just make sure they can handle the current, as there are some quite tiny types rated for <100mA

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It's no problem, just let me know how it works out.. You've been very helpfull yourself, so i would be happy to do something in return..


The tiny axial coils i have look like resistors and the shop i bought them from has no ratings for them..

But i did order some 5uH axial coils rated at 4.0A from Conrad, while waiting for CoilCraft.. They probably wouldn't work in the circuit as power inductors, but as chokes... Why not. I'll try them.

Thanks!


EDIT: I just got a call from Conrad this very moment, saying that these chokes just came and are waiting for me in Austria.. Time for another trip.

I found some nice noise suppression chokes from Conrad. The datasheet says they are meant for switching power supplies, to prevent the spread of parasitic noise:
http://www2.produktinfo.conrad.com/...549999/536466-da-01-en-Drossel-horizontal.pdf

But these are big and also not very cheap..

I'll go with the ones i already ordered.. This is their datasheet:
http://www2.produktinfo.conrad.com/...151-da-01-en-ENTSTOERDROSSEL_MESC_150M_01.pdf

I ordered 8, with an inductance of 5uH.. Even if i use two for each circuit, i can still get four nice drivers, with a very clean output...

You think they'll be good?


Now that i'm looking at their datasheet... These are big too.. They would probably also work as power inductors, right?
Of course they would produce more noise, since they're axial and not shielded...

IgorT said:

I found some nice noise suppression chokes from Conrad. The datasheet says they are meant for switching power supplies, to prevent the spread of parasitic noise:
http://www2.produktinfo.conrad.com/...549999/536466-da-01-en-Drossel-horizontal.pdf

But these are big and also not very cheap..

I'll go with the ones i already ordered.. This is their datasheet:
http://www2.produktinfo.conrad.com/...151-da-01-en-ENTSTOERDROSSEL_MESC_150M_01.pdf

I ordered 8, with an inductance of 5uH.. Even if i use two for each circuit, i can still get four nice drivers, with a very clean output...

You think they'll be good?


Now that i'm looking at their datasheet... These are big too.. They would probably also work as power inductors, right?
Of course they would produce more noise, since they're axial and not shielded...

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I don't think they will be overly effective. Depending on which LM3410 you have (the 525kHz or the 1.6MHz), it looks like the choke will have an impedence of about 15-40 ohms (a bit of extrapolating from the graph below - reds lines are mine) at those two frequencies. How bad was the ripple? You may not need the choke.

...a lot more noise! use them as noise suppressors only. btw, some of the items i ordered from coilcraft are low pass filters. one of them has cut off frequency of about 70MHz and will definitely notch out the highest harmonics of LM3410, but using a 7th order elliptical filter where a simple inductor would suffice is too much of overkill.
edit:
chimo, we are talking about switching spikes /ringing with freq >200MHz/ with repetition rate of 1.6MHz. the caps on the bord are perfectly capable of suppressing 1.6MHz, but the problem is the nanosecond switching of current in excess of 1Amp and impedance of PCB tracks. These high freq spikes are very treacherous to tackle with. tomorrow i will post scope pics.

chimo said:

I don't think they will be overly effective.  Depending on which LM3410 you have (the 525kHz or the 1.6MHz),  it looks like the choke will have an impedence of about 15-40 ohms (a bit of extrapolating from the graph below - reds lines are mine) at those two frequencies.  How bad was the ripple? You may not need the choke.

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I didn't have the chance to have it tested yet.. We are too busy at the moment. I hope we can test the circuits tomorrow..


I have both ICs and i'll test both of them, to see what the output looks like.

Great, I look forward to seeing the pics. Cheers,

Paul

phenol said:

...a lot more noise! use them as noise suppressors only. btw, some of the items i ordered from coilcraft are low pass filters. one of them has cut off frequency of about 70MHz and will definitely notch out the highest harmonics of LM3410, but using a 7th order elliptical filter where a simple inductor would suffice is too much of overkill.
edit:
chimo, we are talking about switching spikes /ringing with freq >200MHz/ with repetition rate of 1.6MHz. the caps on the bord are perfectly capable of suppressing 1.6MHz, but the problem is the nanosecond switching of current in excess of 1Amp and impedance of PCB tracks. These high freq spikes are very treacherous to tackle with. tomorrow i will post scope pics.

Click to expand...

woop said:

I might get a liteon drive, because they are cheap. is there much difference in power output between 18x and 20x drives?

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I just got a reply from Gazoo about the open cans... He says, they are the same in the 18x writers..


This is what he wrote:

open cans can come from 18X writers. The 18X Pioneer 112D, 20X 115D, and the Sony 20X all had the same diode as far as I could tell. They all ran at 2.83 volts with 350ma's of current. I know my Sony diode is a "hot" one, but the output on the one Jay tested is no better than the Pioneer diodes. They all have the long die. In my opinion they are all the same diode.

I did harvest a few open cans from Lite-On drives but I don't remember that much about them except they were a pain to harvest. Plus I didn't have my LPM back then.

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So it seems it doesn't matter.. Maybe you can get a short chip, but there is no way to tell if long is really better for now... But you should ask about the Liteon some more.. Maybe look on the CFP in this thread: http://www.candlepowerforums.com/vb/showthread.php?t=166188

This is what it says there:
- Lite-On LH-20A1P Open can for both IR and Red

If this is the one you have available for cheap, i guess it's your best choice.. But as Phenol said, it's the short chip.. If you want the long one go for a more expensive writer.


This is the one i found in my Sony NEC Optiarc AD-7191A ($42US with shipping). It's the usual long chip type, with the usual bent edge of the pedestal.. It survived the extraction, i put a 10uF SMD capacitor across it's leads and already tested it at 410mA..
It was glued AND soldered in place, so it's a little rough about the edges.. But it survived.. Next is the portable peltier cooling system for it and hopefully the 3410 driver...

he he he. I actually have a pelter, capable of 90W cooling power (it draws like 130W or something stupid like that)

with the dvd recorders, they probably don't have all the advertised ones in stock, so i will have to rock up and see. or call them...

I need to get myself a o-scope
I was playing around with an old TV yesterday, feeding signals straight to the coils. i wonder if that would be capable of displaying 2Mhz

woop said:

he he he. I actually have a pelter, capable of 90W cooling power (it draws like 130W or something stupid like that)

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Oh, mine is small, only 15x15mm 5mm thick, and has 3.9W of cooling power..

I'm gonna put some heatsinks on the hot side and ventilate it with a tiny helicopter tail propeller, powered by a pager motor.. This way, the entire cooling will be able to run from a single AA Ni-MH cell.

It's gonna be very small, but more than capable of pumping away all the heat a LD creates. Of course i'll limit it's power, don't want to "freeze" my new open can..

chimo said:

Great, I look forward to seeing the pics. Cheers,

Paul

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these are two scopeshots of what's on the output /CH1 -> AC coupled, DC component removed/. in the first one channel 1 shows the output noise almost directly across the output cap. the metal shielding barrel of the probe was touching the pcb GND as close as possible to the output cap, and the tip was also as close as possible to the 'hot' end of the same cap. moving the test point by only a millimeter or two resulted in twofold increase in noise amplitude. channel 4 shows the voltage across L2. spiking occurs during rising and falling edges.
in the second pic is one of the spikes dilated in time.
The test conditions were as follows:
Vin=2.72V
Iout=278mA
Vout=2.74V /3x1N4005+1N5819/

pic2 ...

phenol said:

these are two scopeshots of what's on the output /CH1 -> AC coupled, DC component removed/.

Click to expand...

So what is your conclusion from this?

How much of this do you think is due to the inductors you're using? What kind do you have on your circuit again?


I wasn't able to test mine today unfortunatelly. My brother had an accident and ruined my car, so i was running around all day, trying to get things sorted, and i'm still not done... Back to work.

i'll soon be testing another layout and only then will i draw conclusions. nevertheless, i do believe that the cap you have on your diode can filter this. anyway, give it a try with an ir first at a reasonable current /<200mA/. im using home-brew inductrs /toroidal,~20-40uH/. i think that the noise in the pics is a consequence of fast shwitching high current in combination with parasitic trace inductance .in the meantime i succeeded in swapping the places of LD and Rset. Now the case of LD is at ground potential at the cost of an additional IC.
PS - The car is probably wrecked, but i hope bro is ok. it is never a good idea to lend your car, your wife and lasers to irresponsible people. thats why my brother never gives me his.

phenol said:

i'll soon be testing another layout and only then will i draw conclusions. nevertheless, i do believe that the cap you have on your diode can filter this. anyway, give it a try with an ir first at a reasonable current /<200mA/.

Click to expand...

That's what i'll do... I found an "open" can IR in my Sony NEC.. It has a window glued on top, but it can be removed.. I don't know what that means, but i don't care.. I use the IRs for testing only, looking at them through a CCD.

BTW: My engineer also said the caps would probably suffice, as long as they are low ESR and low ESL.

But he also said, that if i want to use a choke, i should try a bobbin type core, with two windings and the caps.. He said he can usually get the ripple so small this way, that it's hard to observe on the scope..

in the meantime i succeeded in swapping the places of LD and Rset. Now the case of LD is at ground potential at the cost of an additional IC.

Click to expand...

What IC did you use for this?

PS - The car is probably wrecked, but i hope bro is ok. it is never a good idea to lend your car, your wife and lasers to irresponsible people. thats why my brother never gives me his.

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Yes, the brother is ok, and the car is not.. It was just a small collision, but enough to smash the front of the car in.. Now i'll be without for a week...

IC can be almost any cmos op amp capable of low v operation....MCP601 in the case being