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

Laser Pointer Store

# Heatsinking with non-metals?

#### HumanSymphony

##### 1
rkcstr said:
This was at 400mA output, with ~6.5V input voltage and ~3V output.
thing is, i'll be using 3x10440 maxing at 12.6V (which i don't know if it can even take that in the first place lol) but i may end up just using 2x10440 to be safe i suppose.

#### rkcstr

##### New member
HumanSymphony said:
thing is, i'll be using 3x10440 maxing at 12.6V (which i don't know if it can even take that in the first place lol) but i may end up just using 2x10440 to be safe i suppose.
What kind of diode, what driving current?

You can (simply) calculate the power dissipation as Pd = (Vin - Vout) * Iout.  So, as long as the input/output differential isn't very big and the current isn't really high, you should be OK.

Also, the maximum rated input voltage for my drivers with the MOSFET input protection (the ones you'll be getting) is 12V, while the older ones are 16V.  You may be able to get away with 12.6V, but you it may be safest to bypass the MOSFET by bridging two of the terminals, just make sure you don't mistakenly switch the input polarity

#### HumanSymphony

##### 1
I'm driving a blu ray at 125mA. i figure i need a consistent 9 volts to drive it. problem is 2x10400 will go 8.4v max and steadily drop. Also, how does one go about bypassing the MOSFET?

#### rkcstr

##### New member
HumanSymphony said:
I'm driving a blu ray at 125mA. i figure i need a consistent 9 volts to drive it. problem is 2x10400 will go 8.4v max and steadily drop. Also, how does one go about bypassing the MOSFET?
I suppose I could just not put them on, if you want it that way (I can still include them if you want them later). Then all that needs done is to bridge the pad for the drain and source pads (the one connected to the positive battery terminal and the other that connects to the input leg of the regulator IC). Or, I can leave it on and just bridge it for you?

#### HumanSymphony

##### 1
please bridge it for me if you would be so kind. one thing though, why don't you do this by default if it helps so well?

#### rkcstr

##### New member
Sure, I can do that.

The reason I don't do it is because it effectively defeats the MOSFET. It acts like a switch on the positive input only closing when the polarity of the wires is correct, otherwise remaining open and no flow, preventing damage to the driver and laser diode upon polarity reversal. It's a safety feature, so without it, you'll just need to be more careful to not switch the positive and negative leads!

#### brtaman

##### New member
Yo I found the leftover heatsink, just shoot me the measurements required i'll cut it...I don't have a rckstr driver.

brtaman

#### HumanSymphony

##### 1
brtaman said:
Yo I found the leftover heatsink, just shoot me the measurements required i'll cut it...I don't have a rckstr driver.

brtaman
The IC is 6x6mm but go ahead and make it 6x8 cuz there's a little room off to the side. thanks ;D

#### pseudolobster

##### New member
Since no one mentioned my previous comment I'd just like to mention diamond again... I looked it up and it is the single best thermally conductive material known to man... Diamond powder is way cheaper than you'd think it would be... mixing cheap silicone thermal grease with diamond powder ends up being cheaper than arctic silver and several times better at conducting heat.

Still, I'm not sure you could use a bunch of thermal paste in place of a heatsink, so I'm not sure it's relevant to the purpose of this thread... but who knows, it's many times more conductive than anything else.. check out this part of a chart I snagged from wikipedia:
Material Thermal conductivity W/(m·K)
Thermal grease 0.7 - 3
Thermal epoxy 1 - 4
Glass 1.1
Ice 2
Sandstone 2.4
Stainless steel[2] 12.11 ~ 45.0