FS: Blu-Bullet Mini Carbon! NEW burning blu ray!

Who was attacking who here?

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I think that is crystal clear from the contents of your post #26 above.

I also think Ramsey would likely not have made the comments he did if you had not egged-him on to do so, with your dishonest and extremely offensive post instructing him to ignore my advice, and that appears deliberately crafted to pick a fight.

He appears to be fairly new here, so is likely unfamiliar with the instigator who's advice he was following, or have been around long enough to be familiar with this -

http://laserpointerforums.com/f59/should-tech_junkie-unbanned-38798.html

An issue that may need to be re-addressed.

BACK OFF

Thanks, brtaman!

Your technical points are spot-on!

+rep!

Considering some of the points you made, along with some of what Ramsey said in his latest post (#30), also got me to wondering about something.

What if he's NOT using the same design for an adjustable voltage regulator in the data sheet as he claimed? What if he's altered it, and was reluctant to tell us about his proprietary improvement? Specifically, what if he ADDED something to it?

If you think about the difference between an LM317 voltage regulator design and a current regulator design, you will see what I'm getting at!

Now, this still doesn't mean that this would WORK (and the points you made about LDs would still apply), just that the REASONS would be a bit different. This could also explain the great difficulty we have been having in explaining this to him, if he is talking about an altered design?

So what say you, Ramsey? Are you using that exact design? Or did you add something to it that's not displayed in that schematic on the data sheet?

I do like his host. And God knows that we could use some additional options for buck/boost drivers (except less expensive than Flex, not more!), as we are currently limited to a single source.

I know one of the members is working on that right now -

http://laserpointerforums.com/f42/erdabyzs-switching-laser-drivers-41820.html

All Ramsey needs to do is get a reliable driver in there that would actually protect the laser diode, and I think he might have something pretty sweet!

seoguy said:

Thanks, brtaman!

Your technical points are spot-on!

+rep!

Considering some of the points you made, along with some of what Ramsey said in his latest post (#30), also got me to wondering about something.

What if he's NOT using the same design for an adjustable voltage regulator in the data sheet as he claimed? What if he's altered it, and was reluctant to tell us about his proprietary improvement? Specifically, what if he ADDED something to it?

If you think about the difference between an LM317 voltage regulator design and a current regulator design, you will see what I'm getting at!



Now, this still doesn't mean that this would WORK (and the points you made about LDs would still apply), just that the REASONS would be a bit different. This could also explain the great difficulty we have been having in explaining this to him, if he is talking about an altered design?

So what say you, Ramsey? Are you using that exact design? Or did you add something to it that's not displayed in that schematic on the data sheet?

I do like his host. And God knows that we could use some additional options for buck/boost drivers (except less expensive than Flex, not more!), as we are currently limited to a single source.

I know one of the members is working on that right now -

http://laserpointerforums.com/f42/erdabyzs-switching-laser-drivers-41820.html

All Ramsey needs to do is get a reliable driver in there that would actually protect the laser diode, and I think he might have something pretty sweet!

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Thank you for keeping this post on a level of constructive criticism, it's greatly appreciated.
The only difference from the outlined design is that I have added a pot to the output pin (wiper and 2 to the output pin, while 3 feeds the pos. on the LD). This is what controls the ma to the diode. Voltage is fixed by the feedback pin sensing resistance ( by two resistors) between FB and the out pin as well as FB and ground, and not by sensing voltage drop or resistance across the LD. With the diode unable to interfere with those two isolated values the voltage value delivered will not change. With the voltage fixed then I am able to limit current via the pot. I have added a simple diagram of what I mean at the bottom (sorry ms paint skills aren't very good). Now I'm not claiming it to be the best in the business, but it does the job quite well. I have tested the driver running a phr for 2min's run time @ 90ma with no rise or fall in ma or v output, while the LD temp rose to 110deg's at the heat sink. I have performed this test 4 times with no variations. I powered the LD for only 2min run time each test because that is what I have read is recommended for longevity.

P.S. forgot to add the cap across the output in the diagram!

I totally understand your concerns for the quality and capability of what is being sold here, I wouldn't want anyone to get a bad deal either. I certainly am accepting of constructive criticism. Thank you.

seoguy;563727- [URL said:

http://laserpointerforums.com/f59/should-tech_junkie-unbanned-38798.html[/URL]

An issue that may need to be re-addressed.

BACK OFF

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So not only are you rude and condescending, but you are threatening me too.

You are such a nice guy....

Your points are valid but the way you present then turns people off. Thats a fact and banning me, or anyone else who disagrees with you, does not change that fact.

Seoguy, check out the latest posts here http://laserpointerforums.com/f42/erdabyzs-switching-laser-drivers-41820.html

Love that beam shot! I like the blue core in the beam that slowly dissipates as it travels down the length of the beam :kewlpics:

Gryphon said:

Love that beam shot! I like the blue core in the beam that slowly dissipates as it travels down the length of the beam :kewlpics:

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Thanks, it's one of my favorite pics.:yh:

Thank you for keeping this post on a level of constructive criticism, it's greatly appreciated.

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Your welcome! Agreed, and likewise appreciated. :yh:

I think you will find that the overwhelming majority of ppl here at LPF are quite helpful & friendly. But like any group this large, there are a very small minority of folks who unfortunately like to pick fights and instigate trouble. You can usually tell them, as they are the ones that engage in personal insults and other ad hominem attacks, rather than civil technical discourse.

The only difference from the outlined design is that I have added a pot to the output pin (wiper and 2 to the output pin, while 3 feeds the pos. on the LD).

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Based on your post #30, that is what I suspected might be going on.

The placement of resistors is VERY important in regulator design. If you take a look at the first schematic of an example voltage regulator on the first page of the LM317T data sheet, and compare that to the design of the DDL current regulator, you will see what I am talking about!

While you have a constant-voltage source supplying it, what you have for CURRENT limiting then is a series resistor. Using a series resistor to control current is the same approach taken by this much-despised design -

Blu-Ray Laser Phaser!

or those cheap driverless Chinese red pointers that burn-out after a while.

While using an actual current regulator to drive a LD is required, having a voltage-regulated power supply feeding into it is not, and is usually done for fancy/high-end devices (like pro scanners, or labbys), or for AC line operated devices, where voltage surges, spikes, transients, etc. are a greater problem.

For battery-powered devices, the issue is a very small/short voltage spike that may sometimes occur when the power is first applied, and which can easily be absorbed by a cap. A cap is, in fact, the only form of voltage regulation in many laser driver designs, such as the DDL.

Having a voltage regulator that feeds into a current regulator is the top-of-the-line for a linear design, but likely overkill for most battery-operated handhelds.

Now, I expect you are chomping at the bit right about now to tell me something, and I DO understand your position as expressed in your posts above, so let's jump right into the heart of the problem, shall we?...

Voltage is fixed...

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At the OUT pin, correct.

by the feedback pin sensing resistance ( by two resistors) between FB and the out pin as well as FB and ground

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Not exactly. R1 & R2 form a voltage divider, which provides a portion of the output voltage (reduced to R2/(R1+R2) ) to pin FB (see pg. 9 of the data sheet, start of 2nd paragraph on right). The device adjusts the power to the output pin so that the voltage sensed at FB is equal to the internal reference voltage - this is how the device adjusts for errors/changes and keeps the voltage the same!

and not by sensing voltage drop or resistance across the LD.

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Not across the LD - correct.

With the diode unable to interfere with those two isolated values the voltage value delivered will not change.

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No, actually if a change in the load causes the voltage to start to change, the resulting shift in the single value (voltage at sense pin) will cause the device to correct (output more or less current), in order to maintain the desired voltage.

But you are correct that the LD cannot alter the RATIO of R1 to R2, which is what sets the voltage.

With the voltage fixed...

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Correct.

then I am able to limit current

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Maximum current, yes. Actual current, no.

This is what controls the ma to the diode.

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No.

If you were powering a static resistance load, then what you are saying there is correct.

But here is where it gets tricky.

A Laser Diode is NOT a fixed resistance. It is an active device, which consumes a specific amount of voltage (forward voltage) that it wants to from the circuit at that time, and which as brtaman rightly pointed-out, can CHANGE based on circumstances (including the amount of current being drawn by the device, output power level, and temperature).

This is the reason that a "dummy load" for adjusting a laser driver has to have active diodes on it, rather than just static resistors - to produce this same kind of "consuming voltage" effect!

As a result of all of this, you cannot consider an device like a laser diode to be a simple resistor, for purposes of calculating Ohm's law.

So what you have to do, then, is determine the amount of voltage drop across the resistor, then apply Ohm's law to THAT in order to calculate the current! As the current for loads wired in series is the same, this will also be the current being consumed at that time by the laser diode!

This is, in fact, how you measure current on a dummy load - by measuring the voltage across the resistor!

Unfortunately, you cannot calculate all of this ahead of time. Here's the problem -

Because the voltage across your pot is going to be what's left-over between the total voltage and what the LD is consuming (because they are in series across your regulated 5.6V), when the forward voltage of the LD changes, the voltage across the pot will also change. As the pot's resistance does not adjust itself when this happens (because it's not a current regulator, it's just a resistor!), this change in voltage drop across the resistor increases the current as well!

That is why in laser driver designs like rkcstr and DDL, they attach a sensor lead AFTER the resistor (between it and the diode), so that they can sense this change, and automatically correct for it!

Unfortunately, due to the multiple integrated devices and complex design of the chip that you were using (including the internal interactions when operating in low-noise boost mode as your application required), I was doubtful that it was even possible to operate this particular device as a reliable LD driver. It sounds like Erdabyz was alluding to some of the same concerns, when he indicated -

big and with some functions not required for this kind of drivers, that also difficult the design.

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You had also indicated that this chip was pricey, and I also knew from my own recent research into regulator chips that there were other devices now available that were not only better suited to your application, but also quite inexpensive! :yh:

Seoguy, check out the latest posts here Erdabyz's switching laser drivers

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I noticed that after your last post - thanks! :yh: I am looking into his designs now - will likely have some hopefully interesting comments for him about that shortly!

BTW, I tried to take the time for you to write this post about a fairly complex topic in a manner that was hopefully understandable. Please let me know if you have any more questions about all of this!

Thanks seoguy, I appreciate the detailed description. I do understand the nature of thermal runaway, however I'm not experiencing any issues if I limit the duty cycle to 1min on 1min off. In fact, since I haven't had any offers on it I figured I'd crank it up last week and see how does. I set it at 150ma and it's even better than I thought. It's a phr that lights matches at over 10ft no problem! It could be just a freak diode but I'm not going to complain. Out of 11 phr's I've got this one is the most powerful by far. Normally if I'd run a phr at 150ma with a ddl I would start to see signs of degrading after a short amount of time, when de-focused to a large spot. This one is a nice full ellipse. I have used it no less than 10min per day for a week with no changes in output strength. I did get scared earlier when I was lighting a match and it just cut off. It ended up just being the battery though, it dropped below 2.7v. I was quite relieved when I changed the battery and it fired right back up. It's actually a nice sounding (audibly) driver, you can hear it humm at a high frequency. Now I don't really want to sell it anyway, it rocks!