Casio 445nm Limits??

[millirad]

^ Nice driver!
To the OP:Yeah I'm happy with ~1.2W for longevity of the LD. You could chance higher but it may fail at 1.6W without Labby style cooling.

 

[More Power]

Re: ***** 445nm Limits??

Handhelds can do 1.5A fine, there was even one build with 1.8 that had a decent duty cycle. Check this out - http://laserpointerforums.com/f51/f...ontinuous-driver-duty-cycle-1-5a-56404-5.html
Quick question on the flexdrive is 1.5A the limit for a 445 A140 diode? If not what is? I'm getting mixed answers...

 

[DTR]

Re: ***** 445nm Limits??

Handhelds can do 1.5A fine, there was even one build with 1.8 that had a decent duty cycle. Check this out - http://laserpointerforums.com/f51/f...ontinuous-driver-duty-cycle-1-5a-56404-5.html
Quick question on the flexdrive is 1.5A the limit for a 445 A140 diode? If not what is? I'm getting mixed answers...

Hey your signature looks like my kitchen.:crackup:

 

[More Power]

Re: ***** 445nm Limits??

Yeah I know, to bad that stupid laser blocks the view of your flawless kitchen!

 

[Braddubya]

Re: ***** 445nm Limits??

If you use 2 microflex or microboost drives in parallel hitting 2A is doable. According to Lava one driver will run at its max and then the other will fill in the rest. So really theres no reason to assume that running two micro flex drives at 1000mA would be any harder on the driver than running one at 1000mA which is done all the time.

The problem I see is that the diode seems to lose efficiency beyond 1.8A according to several builds including ^^^ DTR's ungodly 2W....that seems to be missing from his sig for some reason..?

 

[More Power]

Re: ***** 445nm Limits??

The only purpose I would have for this is slight adjustments to the pot, lower for stargazing and higher for burning. If the ceiling is 1.8 than I assume it wouldn't hurt to give it a little more leash as long as I draw it in equally.

 

[DTR]

Re: ***** 445nm Limits??

DTR's ungodly 2W....that seems to be missing from his sig for some reason..?

It is alive and well. It just has a new owner.:beer:

 

[More Power]

Re: ***** 445nm Limits??

when your diode went out on your 445 murder test, when you brought the ma back down did it appear degenerated at all?

 

[leftkidney]

There are other reasons you should take into consideration when setting the diode current rather than just the capabilities of the diode.

Personally I'm more worried about the driver. The efficiency, at best, of the Flex or Boost Drives is about 90-95% which may seem pretty good. But think. 1500mA at about 5v is over 7 watts! That means than the driver is dissipating well over half a watt as heat. That is alot for those tiny components. Furthermore drivers often never get heatsinked properly in handheld builds.

Also the battery! If the diode is chewing up 7 watts than can the batter supply that plus the wattage going to heat by the driver!? A good quality LiMN cell probably could but those cheaper Ultrafire and Trustfire cells will have a hard time keeping the voltage up under such a drain. Or the clicky switch. Those cheap clickys wont last, it's too much power.

Unless you want a duty cycle of <30 seconds, for most handheld builds IMO, they should be run at about 1A diode current max. Otherwise you'll have issues with short duty cycles and battery life.

And besides, side by side, 1.5W is only slightly "brighter" than 1W. Unless you get your kicks by burning stuff all day, what's the point?

Just my 2 cents/rant

-Tony

only thing I dont understand is the clicky switch thingie - its just a open/closed switch, I bet it could handle hundreds of volts and 10+ amps and 1000000+ watts before it melts - its a switch as far as I know it has nothing in there to fail like a resistor so why?

 

[HIMNL9]

..... its just a open/closed switch, I bet it could handle hundreds of volts and 10+ amps and 1000000+ watts before it melts - its a switch as far as I know it has nothing in there to fail like a resistor so why?

Ehm ..... small switches usually holds just fractions of Ampere, some an Ampere or two, but it's not so easy .....

A switch is an electromechanical device subjected to a lot of different possible stresses and damages (and this is a thing that none take in consideration, usually) ..... it's not just matter of thickness of the pins ..... for know how a switch can work or fail (and become damaged) in a particular circuit, you need to know the thickness of the electrical conductors inside and outside the switch, the section of the contact area of the moving contacts, and their typology and movement type (plane, convex, gridded, multipoint, crosswaved, self-cleaning, rigid, elastic, sliding, pressing ..... just for say some) ..... then you need to know the circuit that is connected to the switch (it's a mainly resistive, capacitive or inductive load ? ..... all of them cause different stresses to the contacts, both in closing and opening action) ..... then you can start to have an idea about how your switch act, or fail, in the action .....

Damages can be melting, degradation of the metal surface coating of the contacts, "dirt" and oxidation of the contacts, springs that lost strenght and cause bad contact for too low pressure, "displacement" of the contacts (when a contact act bad and do conduction only on a reduced part of the contact surface, this point become more hot than normal ..... for high currents, this can become hot enough to "melt" or soften the plastic that hold the contacts in place), and so on ..... it's a very complex matter .....

Just for give an example, (cause if i try to write all about switches, tomorrow morning i'm still here finishing the post ) ..... a "clicky" switch like the one you can usually find in a laser host, can go from 500mA to 5A of possible current holding ..... but, if your circuit have a big filtering capacitor at the input of a driver that work with 1A, the instantaneous short-circuit from the capacitor, that happens each time you turn it on, can quickly ruin (in the worse cases, melt together) the contacts of a standard 5A switch, especially small ones with "forward" momentary function, so one can end asking himself "why the damn switch died in few weeks, on a circuit that use 1A, if there's written 5A on it ?" ..... without considerate that, closing it on a big capacitor, it can also take "spikes" of 10A .....

Remember ..... never say "it's just a switch" .....

 

[Benm]

Switches you can burn at these current levels, no doubt about that. Ideally you could rig a switch that only affects voltage to the driver, leaving the main path to the diode uninterrupted.

The answer to the limit of the 445 diodes can only be resolved by destructive testing though. I'd simply hook it up, well heatsinked, to a lab supply, and increase current limiting as you go. At some point you'll surely fry the diode, but i have no idea how far that goes.

Personally i'm sticking with 1 amp current for these diodes for now. They've been demonstrated to handle much higher currents, but lifitime data on that is very limited still.

 

[IsaacT]

CD520 did a build just recently where he wired 2 flexdrives in parallel doing 900mA each, IIRC. His unit hit 2.1 watts! And the host is sooooo awesome, really slick. AND, do to the flexdrives sharing the amperage equally, didn't heat up too bad....so no, 1.5A is not the limit.

 

[Toaster]

If you look at DTRs bench test, they go dim after about 2A, then when dropped down, they come back.

 

[IsaacT]

If you look at DTRs bench test, they go dim after about 2A, then when dropped down, they come back.

I remember reading that....however, CD520's 445

I guess there will always be diodes that can go above and beyond the average. But 2A seems to be the average limit, yes.

 

[Toaster]

I dont understand how some, that are powered at 1.8A go over 2W, but DTRs bench showed that much lower watt output per milliamp. Can someone explain this?

 

[IsaacT]

COULD be differences in LPM callibration I guess, but I honestly don't know enough bout LPMs to say.