Using a DC/DC converter to power the laser

woop said:

under the chip seems to reflow well whenever i do it. i think the chip would actually be a hot spot, because it would absorb IR better than surrounding metal tracks.
IgorT, you have testing facilities don't you? when you get one working take it in and try adding caps to see what happens.
it should be possible to run a bluray with enough filtering. would it help to put another choke at the output?
only one way to find out.

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I was thinking about a choke too (how exactly do they work in this case?), but i'll just have it tested at work proffesionally, to see what we can do to clean the output.. When the time allows of course.. If my engineer finds a nice solution, i'll post it.

If those SMD caps on the diodes suffice, i'll go with that.. But no matter how clean i get it, i will still test it on IR and flat chip reds first.

I gotta get myself a new burner, any suggestions?

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Well, do you have any open cans already? I ordered a Sony NEC Optiarc AD-7191A (anything with 719x should be fine and yield a nice open can. Not sure about the 720x series)...

For some reason it still didn't come, even tho it should have been here on saturday.. I'm calling that company tomorrow.


In the meanwhile i found yet another good 16x red in an old NEC ND-355.. I found a flat chip and a can, and usually when this happens, the can is the IR, but in this case the flat chip was the IR, so now i have my third 16x DVD laser.. I've actually been very lucky with these, even tho i got some lemons (flat chips that are hard to mount).. They all take 300mA no problem, but i prefer to run them at a safe 270mA, since there is no visual difference from that point on.


BTW: Did you just wake up? I'm preparing to go to bed... It's one o'clock here.

inductors when used as chokes are almost the opposite of capacitors, they pass DC and block AC. so hopefully putting one in serial will block the AC spikes

here are some of my options for dvd burners
Lite-On Super Allwrite IDE DVD Re-Writer (20x/8x Dual Layer) $27.50 AUD
LG GSA-H62NBB SATA DVD Re-Writer (18x/Dual Layer) $37.40
LG GSA-H55NBBK IDE DVD Re-Writer (20x/Dual Layer) $40.70
Pioneer DVR-115D IDE DVD Re-Writer (20x/10x Dual Layer) $47.70

woop said:

inductors when used as chokes are almost the opposite of capacitors, they pass DC and block AC. so hopefully putting one in serial will block the AC spikes

here are some of my options for dvd burners
Lite-On Super Allwrite IDE DVD Re-Writer (20x/8x Dual Layer) $27.50 AUD
LG GSA-H62NBB SATA DVD Re-Writer (18x/Dual Layer) $37.40
LG GSA-H55NBBK IDE DVD Re-Writer (20x/Dual Layer) $40.70
Pioneer DVR-115D IDE DVD Re-Writer (20x/10x Dual Layer) $47.70

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Those LITE-ONS are equipped with short chip open cans and flat frame-type ir. gsa-h55n, like pioneer, has a long chip version. lg also has a canned ir. harvesting diodes from the LG will require cutting on their heatsinks

Those LITE-ONS are equipped with short chip open cans and flat frame-type ir.

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what do you mean short chip?

woop said:

Those LITE-ONS are equipped with short chip open cans and flat frame-type ir.

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what do you mean short chip?

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There are two types of open cans.. Long and short. Supposedly, the long one is a little bit better, but i'm not sure..


Just make sure you get one, where the red LD is not that flat frame type.. Those are pretty much useless, as you can not mount them anywhere..

On the other hand, for my first laser, i did succeed with mounting a lens assembly approximatelly in front of the lens, good enough, to make a burning laser. Still, i never want a flat chip LD again.


I just got my Sony NEC AD-7191A... I'll be dissecting it later today.

phenol said:

Those LITE-ONS are equipped with short chip open cans and flat frame-type ir. gsa-h55n, like pioneer, has a long chip version. lg also has a canned ir. harvesting diodes from the LG will require cutting on their heatsinks

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Wow.. I wanted to recommend Woop searching these drives, to see if they all have open can LDs, but you already had all the answers..

Do you perhaps know if the NEC 719x has a short or long open can? I read the long are supposed to be better, but is that true, or is it just a guess, because it's bigger?

It is just a guess so far. i have both - LG and Lite-On, but i havent pushed any of them to the limit. what i do know for sure is that the liteon LD has highter forward drop compared to LG at the same current. the Vf of the LG matches pretty close w/ the pioneer VIP curve drlava made a week or so ago.

woop said:

inductors when used as chokes are almost the opposite of capacitors, they pass DC and block AC. so hopefully putting one in serial will block the AC spikes

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The opposite of capacitors? Don't capacitors absorb these spikes a bit as well? Or did you mean capacitors in series?


You know, i actually dreamt a similiar explanation, when i went to sleep yesturday...

It would probably require a very low DC resistance, right? But what value? Air core or ferrite? Is there a possibility it would interfere somehow with the rest of the circuit?


I got many huge coils of different values and very low resistance from CoilCraft yesturday, and today i got the tiny 4.7uH coils for the LM3410 (my girlfriend forwarded them to me).. I can finally put this thing together!


I'll ask my engineer what kind of choke he would recommend for this purpose, and i hope we can test this thing properly tomorrow.

phenol said:

It is just a guess so far. i have both - LG and Lite-On, but i havent pushed any of them to the limit. what i do know for sure is that the liteon LD has highter forward drop compared to LG at the same current. the Vf of the LG matches pretty close  w/ the pioneer VIP curve drlava made a week or so ago.

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I see.. Is there any way for me to check which one i got in my new NEC? How do i measure this?


Also, do you know anything about using a choke for smoothing the output of our circuit? Would it help, or could it somehow interfere with the operation of the rest of the circuit?

yeah i mean in series.
a ferrite inductor of high frequency. i don't know what value i suppose you should ask your engineers
it shouldn't interfere with the circuit and i don't think the resistance matters too much, beyond efficiency.
what do you think phenol?

a choke /with ferrite core/ normally helps to suppress rfi. 1-10 uH should do fine. you need one with very low parasitic capacitance...or maybe two - one for + and one for - terminals of LD. the caps across the LD should suffice, though ...

woop said:

yeah i mean in series.
a ferrite inductor of high frequency. i don't know what value i suppose you should ask your engineers

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I already asked him, he's gonna look at it and tell me later.

phenol said:

a choke /with ferrite core/ normally helps to suppress rfi. 1-10 uH should do fine. you need one with very low parasitic capacitance...or maybe two - one for + and one for - terminals of LD. the caps across the LD should suffice, though ...

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Does this mean the same coils that are on the circuit could be used on both terminals as chokes?

They are very small, and i have more than enough of them..
Of course, if the caps would suffice, that would be great, but i just want to be safe.


BTW: Did your coils arrive already?

generally they could be used as filter chokes, but since they have a multilayered winding, the highest freq spikes may still make it to the diode due to the parasitic capacitance between layers and adjacent windings. the best way according to me is to use tiny toroids /7mmx4mmx2mm or so / and put one layer of wire with gaps between windings.
my coils arrived this morning. only two of all items i ordered could be used for a switcher - one is a 3-amp 68uH and the other is a 4Amp toroid monster the size of a donut . im going to find a girlfriend these days and use her address to get a few suitable inductors... jk...

phenol said:

generally they could be used as filter chokes, but since they have a multilayered winding, the highest freq spikes may still make it to the diode due to the parasitic capacitance between layers and adjacent windings. the best way  according to me is to use tiny toroids  /7mmx4mmx2mm or so / and put one layer of wire with gaps between windings.

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I see.. In this case, Conrad has some nice choke, that are meant for this exactly...

phenol said:

my coils arrived this morning. only two of all items i ordered could be used for a switcher - one is a 3-amp 68uH and the other is a 4Amp toroid monster the size of a donut .  im going to find a girlfriend these days and use her address to get a few suitable inductors...   jk...

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My first sample order also only had HUGE coils.. I don't know what i was thinking, when i was submitting it.. I was only looking at the inductance, DC resistance and the current rating..

On the other hand, they did allow me to make a second sample order on my company.. You should also try making another sample request, now that they aprooved you.. If it doesn't work, i have some of their internal e-mails, of three different people, that are more friendly, than the one, that put's our sample orders on hold..

Also, if they really sent my girlfriend the samples twice, she should recieve the second package today.. In this case, i could forward some of them to you, since i won't need that many. I will need a maximum of 14 (7 circuits) or maybe even only 6, since the YSD requires a bigger one. So, if they don't let you make another sample order, contact me, and i'll send you some for free.

jeez, how many did you order when they rejected you igort?
i only ordered 6.

how about one trioid with both wires wrapped around it? or one of those filters you find on dc power and signal cables

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

woop said:

jeez, how many did you order when they rejected you igort?
i only ordered 6.

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When they rejected me, i ordered 8 on my girlfriend and wrote a mail in her name, explaining what it's for, and who her proffesor is, and his phone number.. Then someone from CoilCraft contacted her, and said, they don't see a sample request, so i filled out another sample request, this time for 10, and wrote them, that i again didn't recieve a confirmation mail..

Then they shipped these to her, and didn't even tell me, and in the meanwhile, they aprooved my first sample order, that didn't have correct coils for the 3410, so i made another sample request on my company with the correct ones, because i didn't know, if they'll aproove the request for my girlfriend..

After i did that, my girlfriend got a reply, that her samples shipped out on the 20st and the 21st.. If i understand this correctly, it would mean, that they shipped twice, first 8 and then 10..

Then i recieved an email, saying that my companies second sample request was also aprooved...


So, i didn't do it on purpose.. It was just a funny mistake.. Wait, let me check.. Hmm, the package for my girlfriend says it was shipped on 21 and contains 10.. This means they only shipped once. Ok, i was wrong.. 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...

woop said:

how about one trioid with both wires wrapped around it? or one of those filters you find on dc power and signal cables

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This would be easy to do, and i have some toroids, but they are big.. Conrad sells tiny ones, with different values.. I think i'll go with that, if the capacitors are not enough.

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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No idea.. Could even be the same diode, only driven differently.. I mean, people were driving these with 600 and 700mA (with peltiers) before there were 20x DVDs.. At least i think so.. Not sure.

I'll ask Gazoo, he has lots of experience with open cans. He should know.