Considering the voltage sucking 8x, does it require a modified test load?

[TheGr8Revealing]

My question I guess stems from what has been seen of the 8x diodes requiring more voltage at higher mA's. Does a test load for accurate mA setting need to be made? Should more voltage drop diodes be attached?

 

[jander6442]

I feel this thread need a little bumbage...it has merit

 

[TheGr8Revealing]

ha. thanks jander. now to see if anyone agrees with us on this.

 

[Meatball]

From what I understand, (and believe me its not that much)... the voltage drop across the diode is what tells us how many diodes to put together in series..

I don't believe it requires a modified test load. If we fed a blu ray test load... (the 6 diodes with a one ohm resistor) the same 350mA of current we usually do, you would probably see the same kind of voltage across the entire load.

The 6X would probably draw the same voltage if it were pushed hard enough..

I think we are only now noticing this difference in voltage simply because we haven't had the opportunity to push blu ray diodes this far... until now.

Maybe I'm wrong though...

Perhaps someone like Electrofreak had better come along and give a better answer..

Tyler

 

[jander6442]

enter Igor

Dr lava?

 

[Darkarmyofone]

Enter JAYROB ^_^

Or even better... DAGUIN

THEY would know im sure

But i run 8x's every single day, and have had no issues with false mA readings.

 

[HIMNL9]

If the LD have a bigger FV, just add a diode in serie of the others in the test load

6 diodes = 4,2 / 4,5 V

7 diodes = 4,9 / 5,2 V

 

[daguin]

If the LD have a bigger FV, just add a diode in serie of the others in the test load
6 diodes = 4,2 / 4,5 V
7 diodes = 4,9 / 5,2 V

I think the question is whether using the test loads that we already have will cause problems with the new diodes or not. If people are "setting" the current with 6 diodes in their test load, but the laser diode is actually pulling 5.6V, will the current being delivered to the laser diode be correct?

This is outside my electronics knowledge. I could test it, but I don't have equipment and tools here. Maybe someone else could set up this test. You would need a 203BK diode. Set a driver with a test load (~350mA). Hook up the laser diode. Test the actual current being delivered to the laser. Is the laser getting 350mA?

I would think that someone with electronics knowledge could figure this out, on paper, without risking a $200 diode.

Peace,
dave

 

[HIMNL9]

Well, basically, if the driver is just a current regulator, the number of diodes is insignificant, cause, being in series, the same current flows through all them, so if it was only matter of current, also just the 1 ohm resistor must be enough.

The diodes are helpful if the driver have limits in the voltage that it can give ..... i mean, if you're using 12V and set the current to 500mA, through only the 1 ohm resistor, or through 6 diodes and the resistor, it's always 500mA, cause the driver can deliver enough voltage for let you set the current correctly, and then self-regulate the voltage for keep the current constant ..... but if you are using, as example, a boost driver that start with a lithium cell, and have a maximum voltage capability of 5,5V (as almost all those IC's have), then you need to check if with the correct voltage drop caused from the diode, you still have enough voltage for give you the 500mA you want .....

as in your example, if your diode cause a drop voltage (FV) of 5,6V, and your switching driver only can give 5,5V, if you set the driver with 6 diodes, that pull 4,5V, the driver still let you regulatr the current til 500mA, if instead you use a test load that have the same drop of your LD, 5,6V, the drive don't let you regulate the curren til the level you want, cause it don't have enough voltage output.

So, basically, for linear labby regulators, or regulators that have enough output voltage, is indifferent how much diodes you use, where instead, for regulators with a limited output voltage, is important that the voltage drop of the test load is the same (or close as the possible) to that of the real LD

 

[mfo]

Couldn't you just attach an ampere meter to the outputs of the driver (where you'd connect the laser diode) to properly set the current for the driver? I took this piece of instructions from the rkcstr driver manual, found here.

http://rkcstr.googlepages.com/MD_v3_inst_rev1.pdf

"1. The most accurate method involves directly measuring the current with an ammeter (or
multimeter set to measure mA). Make sure your meter is rated to handle at least
500mA and that the measurement range is within your intended setting.
a. You can directly attach the multimeter leads to the driver output (red to positive,
black to negative) and power up the driver then adjust the pot to set your
current while monitoring the meter"

Hmmm?

 

[Jimmymcjimthejim]

Guys, don't forget that with the higher current going through the test load diodes, the more voltage they use (like with the laser diode).

 

[HIMNL9]

Guys, don't forget that with the higher current going through the test load diodes, the more voltage they use (like with the laser diode).

Well, basically also this was that what i meant ..... also LD's increase their FV a bit, increasing the current, so, or you have a driver that use a voltage more high than the FV, or you can have troubles and can't set it for the current that you want (it's a basical law of phisic, after all, you can't suck more energy of that what you have available )

And this is true for all these switching drivers, that starts with one lithium battery (boost types), and, usually, have maximum output voltages of 5,5V (90% of these IC's have this limit, same as the 63010 that is used in lavadrive) ..... need to study some different driver, maybe using led drivers IC's, that don't have the same limits, for these new incoming diodes, that, apparently, have more high FV .....

Anyway, i can't afford at the moment an 8X, so can't do any tests ..... someone with an 8X, can please say me what's the maximum FV (voltage drop through the diode, said in a different way ) that they can measure, for the currents that normally uses ? ..... or some intermediate values, or if there are some graphics already done, that shows also this data, other than just current and output power ? (found something in the forum, but was for 6X diodes)

Thanks.

 

[daguin]

This should have what you are looking for

http://laserpointerforums.com/f38/8x-br-diodes-42806.html

Peace,
dave

 

[HIMNL9]

Uh, no, in this post there are no voltage references, anyway, thanks, cause from link to link i found something (in one of your posts about possible 8X sleds, btw )

that 5,7V, cited from you, and also from LarryDFW, make me think that, without a new driver design, may be a bit difficult obtain some high efficent / high power "handheld" unit, drived from 1 or 2 cells, with a boost converter ..... not with the actual drivers, anyway, that have 5,5V limits.

i mean, according to your data lists, the indicated 300mA are already measured at 5,6V, so, also if not indicated, can guess that at 5,5V, the diode was around 260 to 280 mA ..... so, also if i set a driver at, as example, 350mA, using a normal test load, when i connect the diode, having the driver less voltage than the one requested from the diode, it drop til that current, cause just can't give the needed voltage ..... at least is that what i calculate on-the-fly, please correct me if you think i'm wrong.

Can be interesting made a test ..... if someone can get a 5,6V 5W zener diode (must be a 5W unit, for not have too much drift and not fry it ), connecting it in place of the 1N series, and trying to regulate the flexdrive for see if it still can supply the needed current.

Can't do the test myself at the moment, cause i don't have this type of zener at home ..... i already ordered some 1N5339B, that can hold til 865mA and have a decent stability (at least, seeing the datasheet ), cause i want to do some tests in this range and conditions, but cause the vacation time, here, all the components shops are closed til after the first week of september, so, til when they open, i have to wait

If it works, can also become a new test load type, dedicated to high power BR diodes (also if the more simple way, can just be stick in series 7 common diodes, or also better, 8 ..... after all, if the driver works with 8 diodes, then you are completely sure that it can feed all your 8X with no problems at all )

 

[daguin]

Sorry about that. I thought it was included

Thanks for putting your brain to work on this. We are having some troubling results from the new s03 sled. This may or may not be the issue, but it is a good thing to look at.

Peace,
dave

 

[HIMNL9]

Wait, you mean where peoples says they burned the diodes hitting them with high current ? ..... if yes, now you have made me have a doubt ..... i mean, how much peoples of these ones was using lavadrives ?

I'm asking cause Drlava already said somewhere in a post (don't remember now exactly where) to never use these drivers without load, cause they can be damaged in this way ..... now, if you have a driver that can give out only 5,5V, and you connect it on a load that have an internal dropout of 5,7V (or, anyway, more high that what is needed for keep the driver "loaded", is the same that you run the driver without load .....

From here, i'm just supposing, cause i never had in hands a 63010 for made experiments (mainly cause this IC have grid pins too small for experiment with it at hobby level) ..... but, supposing, if the driver become powered with insufficent load at current regulator configuration, is possible that it go in oscillation ? ..... and if yes, is possible that, in these conditions, it give out spikes high enough to burn the LD ? (need to ask drlava, for this, cause he surely knows 63010 much better than me)

If instead they was using linear regulators, i have no ideas about that ..... maybe a ramp circuit can help preventing this ?