Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

# how do i get more MA's?

#### a_pyro_is

##### New member
I just tested with 3 old 2000mAH NiMH AAs fully charged to 1.4 V gives me 4.2 V, less the forward Voltage drop of the GB LD I'm playing with which from 160-320mA is about 2.8 V leaves me a max of 1.4 V to drop with a resistor. 1.4 V/300 mA = 4.7 Ohm resistor. The batt voltage quickly drops to 3.72 V less the Voltage drop leaves 0.92 V/4.7 Ohms = 196mA.

In real life the current supplied is a bit lower because of the internal resistance of the batteries. But if someone is intent on sending a diode to an early grave, this would seem to work.

But I get MUCH better results when using a regulated current supply. With 6 V into my 4 component LM317 circuit I can burn everything in sight all day long. With the 3 NiMH and 4.7 Ohm resistor it works great for about 10 seconds, and then drops in power quite a bit. and I can't go any lower than 4.7 Ohms as the current spike on power up is around 370mA which I think would in short order kill the diode.

If you don't have a way to measure the spike on power up and you're intent on driving it this way I'd say start with a pot at around 20 Ohms with 3 fully charged NiMH AAAs and SLOWLY decrease the resistance WHILE measuring the current, when it gets to about 160mA stop and measure the resistance. Use the closest higher value resistor you can find/make.

Also note that your diode may have a VERY different Voltage drop and it needs to be measured. This example was just for my diode.

#### toked323

##### New member
so maybe a new diode would work is what your saying?

#### a_pyro_is

##### New member
If your diode behaves just as mine did, then it can be driven by 3 NiMH AAs and a 4.7 Ohm .5 W resistor. But it won't like it and will prob die soon.

The problem is that your diode won't behave just like mine, so you'll have to plug in your own numbers. And it still won't work as well as one properly driven with a constant current supply.

Msybe I just missed it, but why is it that you don't want to use such a driver?

yea maybe

#### jayrob

##### Well-known member
LPF Site Supporter
toked323 said:
how do i get more MA's? do i add a battery and drrop voltage?
I have built one of DDL's DIY torches to his specifications and it measures at the LD: 2.75 volts and 248ma using the Energizer 3.0 batteries. But, for more current, I built the same thing using LarryQ's suggestion (he even sent me a custom heat sink and the resister) The change was to use a single 3.9 ohm resistor at the LM317 instead of 2 10 ohm resistors....along with his custom made aluminum heat sink for the LD. This one measured at the LD: 2.88 volts and 323.5ma! I figure about 170mw according to Daedal's comparison graph that he did for the Phazor vs Senkat diode.
Jay

#### a_pyro_is

##### New member
Kenom said:
you really need to explain what your doing. components. straignt batteries to diode, resistors you've used and how, capaitors used and how. It's impossible for us to tell you what to do unless we understand what your doing. so far what we see is yoru doing this.... which is driving yoru diode straight off batteries. we aren't mind readers dude.
a_pyro_is said:
The problem is that your diode won't behave just like mine, so you'll have to plug in your own numbers. And it still won't work as well as one properly driven with a constant current supply.

Msybe I just missed it, but why is it that you don't want to use such a driver?

toked323 said:
yea maybe
Toked,
I'm sorry, but I re-read the thread and still don't understand what you're trying to do. :-?

You've a forum full of people trying to help you. But they need a bit more info to be able to do so. And I'm afraid that this isn't Avery's Psychic Tech Support Forum.

If you don't want to spread a brilliant idea all across the forum before you've got it working just right then PM me and I'll do my very best to help you. as I'm sure many others would be willing to offer.

I didn't mean to sound harsh, but when people are trying to help you, you've got to make it as easy on them as you can. So give us the whole picture (maybe even with some pictures if they'd help ) and we'll get it sorted out for you.

#### toked323

##### New member
thanks man but you cant fit cr123 batts in there or fit much in a dorccy but i will try it thanks

#### a_pyro_is

##### New member
YAY!!! OK, so you've got one of the 2 AA Dorcys. you can use rechargable lithium 14500s they're about 1.5mm longer than a AA but just might fit. As for an easy to find driver, look at the LM317 in a TO-92 package. Just be sure to try to heatsink it to the metal body of the light.
There are a number of other regulators that would work better, but I'll leave that idea for someone else to think through.

Any ?s about that and you can PM me.

#### toked323

##### New member
i thought the to-92 only withstand 100mA's and its a dorcy metal gear sorry bout that

#### a_pyro_is

##### New member
Correct, the TO-92 packaged LM317 is only rated for 0.1 A. But with a proper duty cycle and a bit of heatsinking, just like the LD, .25A is doable. I just keep it to about 30-45 seconds on and about 1 minute off. While it gets hot, it doesn't get so hot that it goes into thermal protection mode even after 2 minutes on. But I did a pretty good job of heatsinking it with my homebrew thermal epoxy.

#### Gazoo

##### Active member
The LM317 will not work in the Metal Gear. The very best solution is the AMC7135 with a 33 ohm resistor in parallel with the diode. This will supply ~250ma's to the laser diode. This is great for the GB diode. Of course for an open can...no resistor is needed.. ;D

#### toked323

##### New member
well i got it to burn (i was so stupid)

#### a_pyro_is

##### New member
a_pyro_is said:
YAY!!! OK, so you've got one of the 2 AA Dorcys. you can use rechargable lithium 14500s they're about 1.5mm longer than a AA but just might fit. As for an easy to find driver, look at the LM317 in a TO-92 package. Just be sure to try to heatsink it to the metal body of the light.
There are a number of other regulators that would work better, but I'll leave that idea for someone else to think through.

Gazoo said:
The LM317 will not work in the Metal Gear. The very best solution is the AMC7135 with a 33 ohm resistor in parallel with the diode. This will supply ~250ma's to the laser diode. This is great for the GB diode. Of course for an open can...no resistor is needed.. ;D
@ Gazoo. Why wouldn't the 317 work in a metal gear at 7.2 Volts from 2 14500s? Is there just not enough space? I agree that the 7135 works better, but it's a little harder to find. Whereas the 317 can be had at most Rat Shacks.

#### Gazoo

##### Active member
The Dorcy Metal Gear takes 3 AAA batteries.

#### a_pyro_is

##### New member
a_pyro_is said:
so you've got one of the 2 AA Dorcys
Oops, I was still thinking that he was using 2 AAs.
But looking around at batteries has given me some ideas ;D

#### toked323

##### New member
it runs around 260mA now with 3 AAA and a 2.7 ohm resistor