M140 Heat Output

[Jedi]

I have been looking around online for a graph of the waste heat output rate (waste power) over the amperage input for the m140. I want to build a micro peltier cooling system that will give the most efficient compact cooling for a nonstop duty cycle.

What I need to know is at what rate do I need to remove heat to keep the m140 at optimum operating temperature when running at 1.8amps.

Here is the link for the cooling devices. Take a look at the micro. Thermoelectric cooling, coolers, modules, heat sinks, exchangers, Peltier coolers, devices - TE Technology

 

[Meatball]

Laser diode's dissipated heat is given by:

Power = i*Vf

Heat dissipated = (Power - optical output power of diode)

Hope that gets you started.

 

[Bionic-Badger]

Something you should realize is that the Peltier itself will cause heating, so unless you have additional means to move that extra heat away you should probably just seek out a better heatsink.

 

[Eudaimonium]

Yeah, Peltier elements themselves have about 20% or so efficiency.

If they have about 5W of cooling power (that's a term ) on one side for your diode, on other side you need to figure out a way to deal with whole 25 Watts of heat.

It's only good if you need to get the components below room temperature, or even below zero in extreme cases. Otherwise, you're creating 5x more problems than what you started with.

Oh, and I love your avatar. Don't tell me you drew it yourself...?

 

[Jedi]

Ah. I see. 20% efficiency is quite a blow. No doubt I will still toy with the idea. I have another idea to use a water filled copper reservoir that fits snugly around the module and driver. Then heat sinking the reservoir. Or instead of heat sinking the reservoir I plan making the reservoir detachable so that it can be placed in the refrigerator or freezer prior to use. The goal is a streamlined 2w 445 with nonstop duty cycle.

 

[Eudaimonium]

There are currently existing 100% duty cycle lasers already. No need to go for copper water reservoirs That's a bit of a stretch.

The only thing you need is a heatsink big enough, and you can run pretty much anything at 100% duty cycle, provided you take care of the driver well (which actually becomes more difficult to heatsink at those powers). With that in mind, here's a project of mine,

http://laserpointerforums.com/f42/new-host-design-feeler-ge-x1-77903.html

 

[Jedi]

Streamlined and ergonomic are criteria to my design (This is why I was looking into alternative heat sinking). Thus bulky heat sinking is something I want to avoid. I am looking at your Gex host at the moment. It is a clean design. I'm tempted. Though I really just want to go out of my way to have a very unique build.

I have always used my own machine shop to work on my projects, but I'd like to go more of a CAD route and have the specific parts machined (something I have never had done). Do you machine your own parts?

 

[Eudaimonium]

Yeah, my stuff is all machined by hand. CNC a bit expensive

Well if you're looking for "alternative" heatsink, I'm afraid you're not going to find too much information around here.

But, you can get active heatsinking in handhelds, members around here have done it before. It's still not exactly "streamlined" but surely will be lighter than 6 tons of aluminium that is Gex.

It's going to be more of a challenge to wirte it all. But not nearly as difficult installing a water cooling system.

 

[Jedi]

The challenge is half of the fun. So you haven't seen a compact water cooled system before in this community?

 

[Eudaimonium]

In a handheld laser?

Nope. The only things with water coolings around here are CO2 systems, sometimes with outputs in orders of killowatts.

I believe no water cooling is needed for some measly 7-8 watts released by the diode at operation, a big chunk of aluminium is fine. Sure, the hosts around aren't what you call a "streamline" design but I like angles. Makes it feel more high tech. Did I ever mention that I hate Apple?

 

[Bionic-Badger]

Why do you think having a reservoir of water would be any less bulky than filling that area with metal, or making fins or something? The only reason you should be using water is to mechanically move heat away from the device to a radiator that has more surface area than around the heat source. Sure, you might be "mechanically" moving the water by taking the water away and freezing it, but the fact that you're doing that at all means you've already undermined the no-duty-cycle purpose of the host -- and increased the bulk dramatically.

If you've got metal working facilities, maybe find a way to put a fan inside the host. Even then, I don't think an M140 really creates enough heat to be worth that effort. You could just add more metal mass and some fins and that should be enough.

Maybe even think about just putting a heatpipe into the host. I've got a passive-cooled heatsink made for a 10W LED that uses a heat-pipe, and the whole thing is about the size of a host anyway. You don't need something complex like water cooling for an M140 laser diode.

 

[Jedi]

good to know

 

[Cube777]

A bit off topic but is there a way to calculate the amount of heat that can be dissipated by a heatsink?

 

[Bionic-Badger]

Ultimately, a heat-sink can only continue to dissipate heat if the heat is continuously conducted to some other medium, or radiated away. For conduction, the final medium is usually air, which is replenished by convection or mechanical means. Should there not be enough airflow, the heat sink itself will continue to accumulate heat faster than it can be dissipated.

Hobby lasers usually won't have forced airflow to cool a heat-sink. They usually rely on the surface area of the host for conduction with ambient area, as well as the heat capacity of the heat-sink and conductivity of the material to rapidly move the heat from the diode to the rest of the material. There are limits of course, so you need to ensure that your host has enough surface area to radiate/conduct the heat to the surroundings if you're running the laser too long.

Often hobby laser hosts do not have enough surface area to not accumulate heat. This is why such lasers have a duty cycle: to allow the host to cool off.

How to calculate all of this? Well, there's a decent model on Wikipedia you can look over. Ultimately, you need to know the geometry of the heat sink, the materials, and how those affect the ability for heat to be conducted into the surroundings. You'll probably also want to know the specific heat capacity of the materials so that you can determine how much energy the materials can contain before heating up.

Sorry, I don't know the exact formulas for all this, but you can look them up if you want to run through the numbers.

 

[Jedi]

Ideally the heat sink is made with a material that has the highest specific heat. So I am still convinced that a tight fitting low profile water reservoir is a realistic idea. Table of Specific Heats

 

[Bionic-Badger]

You can use water if you want to absorb and retain the heat in the heat sink. It won't have a "non-stop duty cycle" like you wanted in your OP, though maybe a longer one, including the part of the cycle where you wait for it to cool down.