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[dethlore]

I have an M140 wired up to a 1.9A linear LT1185 current regulator.
Turns on and is on as it should be. nothing out of the ordinary, but I recently got a Radiant X4 LPM and measured it. The weirdest thing happens:

It ramps up to just over 1000mW, and then just as quickly as it went up (about 20 seconds), the power falls down to around 600mW. Regulator is heatsinked to a cpu heatsink, and the M140 is in a copper module in a fair sized heatsink. The module is warm, but not hot.

This SHOULD be getting up close to 2W shouldn't it?

Any ideas?

 

[DTR]

Maybe your resistors are overheating. When they overheat the values change and the current will drop. I had this problem with some of the original Moh drivers but I think he went to a higher rated resistor as it was not present in later driver versions. I had to solve it by sinking the resistors as well as the regulator.

 

[dethlore]

Hmm... may be. In fact, I think you're absolutely right. I didn't think of that before because I've run things at 3A+ before, but the input voltage and output voltage was closer... NOW, my regulator is dropping about 7V at 1.9A from my 12V source. duh... haha I really need to get a variable bench supply so I don't do this to myself.

I apologize for the handful of duh threads I've started lately. I took a break from electronics for a while, but I'm getting back in...

 

[dethlore]

one more thing I need to clarify... is it correct that if using a linear regulator, two old and used 18650s will not be able to supply more than about 1A of power? But the new high discharge batts should be able to do that, right?

Is it possible to use just one high discharge batt for 1.9A through a linear regulator instead of needing more since it is capable of that draw?

I haven't seen any specs or tests on these new high discharge batts.

 

[The Lightning Stalker]

With a high current DDL type setup, it isn't the ampacity of the batteries that is the problem. The problem
is that the regulator and resistor(s) are dropping so much voltage that there isn't enough left for the diode.
More voltage is the only solution. It also helps if you can see the current the diode is actually pulling.
You need a good size 1Ω or 0.1Ω resistor such as this in series with the diode. That will give you a good
1:1 or 10:1 current reading, respectively.

 

[dethlore]

With a high current DDL type setup, it isn't the ampacity of the batteries that is the problem. The problem
is that the regulator and resistor(s) are dropping so much voltage that there isn't enough left for the diode.
More voltage is the only solution. It also helps if you can see the current the diode is actually pulling.
You need a good size 1Ω or 0.1Ω resistor such as this in series with the diode. That will give you a good
1:1 or 10:1 current reading, respectively.

I currently have some 5W and 10W 1Ohm resistors, but the idea of using a .1ohm always sounded good to me.
The regulator should have a forward voltage of .75V @ 3A, and the 445nm we always test to run around 5V, although I think it actually runs at 4.5V. I should need a minimum of 6V to lase, and probably another 1-2V for longevity, right? That fits the two Li-Io perfect, so I should have the voltage I need... ?

Just for the record, I did try 3 Li-Io in series for a total of 11.1V (9V-13.2V empty to full) and it wouldn't hit my 1.9A, but a sealed lead acid battery supplies the current just fine. Constant 1.9A, but I think the resistors got hot like DTR suggested, which is actually kinda strange because the LT1185 circuits I have built in the past have stayed cool, even with LEDs with 12V@1.5A

 

[IWIRE]

These batteries will supply the current you need 2 PC Imren IMR 18650 Li ion Battery High Drain Rechargeable 3 7V 2600mAh 38A Red | eBay

I started using them in everything that draws much current. I have one in a build running one battery with a boost drive pulling about 6a and it maintains it's voltage under load. I went through a bunch of batteries finding this battery.

 

[dethlore]

These batteries will supply the current you need 2 PC Imren IMR 18650 Li ion Battery High Drain Rechargeable 3 7V 2600mAh 38A Red | eBay

I started using them in everything that draws much current. I have one in a build running one battery with a boost drive pulling about 6a and it maintains it's voltage under load. I went through a bunch of batteries finding this battery.

I was thinking those would do the trick. I'll have to get a pair and post back if it gives me the current my driver is set for.

Thanks

 

[IWIRE]

I haven't been brave enough to test them and see if they really will supply 38a like they state. But everything else tests out with them. Capacity is what's stated and the internal resistance is low.
They worked for me and I hope they work for you. The seller I posted a link to ships fast. :beer:

 

[The Lightning Stalker]

That should work with fully charged cells. You may need to charge when they reach 3.5V/cell