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What heat-sink for micro-boost?

drummerdimitri

drummerdimitri

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Hello guys,

I am running my micro-boost at it's max allowable current setting and it is getting pretty toasty inside the flashlight host. I was thinking of heat-sinking it with a Zalman ZM-RHS1 VGA RAM heat-sink, because it seems to be efficient at cooling the driver down a bit. Do you have any other suggestions regarding what heat-sink I should use with my driver? I am aware of DTR's coin mod, but that wont work in my case because the host cannot accommodate such a large coin. Let me know what you guys think...

Thanks!
 





RA_pierce

RA_pierce

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You can really use anything you want.

When the heat-sink has reached it's capacity, it will no longer cool the driver. The only effective way to keep the driver cool for an extended period would be to allow the heat from the driver heat-sink to flow to the host - otherwise all you are doing is giving the driver a few more seconds before it gets too hot.

Experiment with some things and see if you can't make it work.

My advice would be to turn down the current.
 
drummerdimitri

drummerdimitri

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I cannot find a way to stick the driver directly to the laser's body because there just isn't enough space. I think my best bet is to place one of those heat sinks on there to draw some heat away to allow for cooler operation and prolonged duty cycle. I am not a thermodynamics expert myself, but what do you mean when you say when the heat-sink has reached it's capacity? Thanks!
 
RA_pierce

RA_pierce

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drummerdimitri said:
I cannot find a way to stick the driver directly to the laser's body because there just isn't enough space. I think my best bet is to place one of those heat sinks on there to draw some heat away to allow for cooler operation and prolonged duty cycle. I am not a thermodynamics expert myself, but what do you mean when you say when the heat-sink has reached it's capacity? Thanks!
Click to expand...

The metal heat sink can only hold so much heat. If it is thermally isolated from the host, the heat has nowhere to go.
To elaborate:
The function of a heat-sink is to increase the volume/mass that the generated heat is dispersed through.
When you laser starts up, excess electrical energy is converted to heat (as you know). This heat builds up, and if it gets hot enough, the driver will shut down or sustain damage.
Adding the heat-sink to critical components gives this heat somewhere to flow to. More mass means more room for heat.
The other part of effective heat sinking is surface area.
If heat cannot flow from driver to heat-sink to air, then eventually the laser's components will become saturated with heat and the temperature will rise until the device fails.
Bonding the driver heat-sink to the host allows heat to travel from the chip to heat-sink to host and then the heat will be wicked away by air flow.
Simply attaching a heat-sink to a driver in a closed, thermally isolated body will extend the duty cycle, but only until the heat-sink becomes saturated.
In your laser, the diode is producing 3W of heat and the MicroBoost will be producing at least 1.5W of heat. In this case, the driver heat-sink may only extend the duty cycle for a few tens of seconds.

In short, more mass is useless without more surface area as well.
 
Last edited:
drummerdimitri

drummerdimitri

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Messages
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RA_pierce said:
The metal heat sink can only hold so much heat. If it is thermally isolated from the host, the heat has nowhere to go.
To elaborate:
The function of a heat-sink is to increase the volume/mass that the generated heat is dispersed through.
When you laser starts up, excess electrical energy is converted to heat (as you know). This heat builds up, and if it gets hot enough, the driver will shut down or sustain damage.
Adding the heat-sink to critical components gives this heat somewhere to flow to. More mass means more room for heat.
The other part of effective heat sinking is surface area.
If heat cannot flow from driver to heat-sink to air, then eventually the laser's components will become saturated with heat and the temperature will rise until the device fails.
Bonding the driver heat-sink to the host allows heat to travel from the chip to heat-sink to host and then the heat will be wicked away by air flow.
Simply attaching a heat-sink to a driver in a closed, thermally isolated body will extend the duty cycle, but only until the heat-sink becomes saturated.
In your laser, the diode is producing 3W of heat and the MicroBoost will be producing at least 1.5W of heat. In this case, the driver heat-sink may only extend the duty cycle for a few tens of seconds.

In short, more mass is useless without more surface area as well.
Click to expand...

Thanks for the clarification! I understand what you mean, and the fact that the heat flows from driver to heat-sink to air trapped inside the host makes it pretty much useless to have one installed in the first place. In that case, do you have any suggestions on how to use the host as a heat-sink for the diode? Right now, the driver is just stuck to the bottom with some thermal tape and isn't transferring enough heat IMO.
 
drummerdimitri

drummerdimitri

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Tikilaser said:
Well, the coin mod from DTR may not fit, but try stacking 3-5 pennies or nickels and then using some thermal adhesive to mount them to the driver, then mounting the stack to the wall of the host right above pill with some more Thermal adhesive. just my 5 cents. :crackup:

EDIT: Be sure to connect the pennies in the stack with the adhesive as well...
EDIT 2: if there is no room, then you can always just stick the coin mod to the bottom of the haetsink so it is upside down and fits. Please tell us what host this is and pics if possible?
Click to expand...

Thanks for the tips, but I have already found a solution to my problem: I have managed to stick the driver parallel to the body of the host with the help of thermal tape, this way the heat from the driver can be dissipated throughout the entire aluminum host. More efficient than just sticking it to the bottom of what used to be the flashlight's driver. I will see if that prevents the flashing that occurs after a few minutes of continuous use.
 
drummerdimitri

drummerdimitri

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Tikilaser said:
Alright, report back soon and we will see :D
Click to expand...

Good news, the entire body of the laser is now getting warm after a few minutes or runtime instead of having just a hot head due to the copper heat-sink. This is a good sign because previously, the heat generated from the driver was not being transferred to the laser's host, but instead exchanged heat with the air trapped inside, heating the driver until the laser started flashing. The heating up of the entire host is proving that the heat generated from the driver is spreading itself through the body, which in turn cools the driver and allows for continuous operation with no duty cycle and no flashing. Thanks for the advice RA_Pierce!
 
drummerdimitri

drummerdimitri

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Tikilaser said:
Uh.....Double same post dude :rolleyes:

EDIT: Good to know its working out better. If need be, you could drill out a computer heatsink and use some thermal adhesive to mount the head inside the heatsink. Then just round off the edges of the heatsink if you want it to be less ugly. If you just want elegance, dont bother, and if you want it in your pocket, this is a great way to kill yourself, but other than that....
Click to expand...

Thanks for the heads-up!

I am happy with the way it is performing ATM, so I will just leave it the way it is unless I encounter some heating problems in the future.
 
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