Do I need heatsinking?

[JimmerG]

So here's the plan....

First of all, thanks Marduke for sorting my resistor concerns. Now can anyone help me understand heatsinking. This is what I'm up against...

The LED shown is a P4 but I'll be upgrading to an R2... the star will sit on the lower metal lip up from the circuit board. So In effect the outer edge of the star will be in contact with the aluminium case - which is in turn screwed into the flashlight body, there's an 8mm air gap under the star. If I 'stick' the star this onto the lip using thermal grease will enough heat be dissapated?

Am I right in thinking that if a flashlight gets warm on the outside, then the heatsinking is working OK? So if the body does not get warm whilst sat stationary - would this mean the led could be over heating and damaging itself?

This light will only ever be used mountain biking, so the ambient air will always be cool and flowing.

What do ya think? Is there a simple way to help heatsinking?

Thanks

James

 

[ahorton]

It depends on how much current you plan to run. My guess is that you will need far more heat sink if you want any more than a dim glow.

Have a look at the custom heatsinks that everyone else is using.

 

[Tekno_Cowboy]

It works for the Wolf-Eyes modules...

If you really want to up the heatsinking, stick a copper plug under the LED. It would be easy enough to make one to fit your application. You'd just need a couple of holes for the wires and enough gap for the extra wire. You'd want to leave a thin lip on it to keep it in place.

 

[Gunner12]

How much current will be going through that LED?

As Tekno Cowboy said, you can make a copper or aluminium plug to help with the heatsinking.

 

[kramer5150]

Its a balance scale

One side of the scale:
Drive Current
Power ON duration (time)

Other side of the scale
Lumen output

I think you could easily fabricate a copper or aluminum plate from some stock, and thermal epoxy it into the pill. Drill 2 holes for the wires and that would give the heat a thermal path away from the emitter. you might have to modify the reflector though in order to get the bezel to fully seat down.

What light are you attempting to mod?

 

[gadget_lover]

The prime considerations are how much metal to metal contact is there, and how well the metal is touching. The more metal in direct contact the better.... up to a point. In this case you want to make sure the star is held very firmly against the lip that holds it. If it is a loose fit, then all the thermal grease in the world will not make much difference.

If the body of the light is warming up, then some heat is being properly transferred. If the body is as warm as the star, then it's doing a fairly good job.

Just to put it in perspective, In the early days of 3 watt LEDs, a very popular 'sandwich' used a thin copper plating on a circuit board as the only heat sink. They were not as bright, but they used that 3 watts of electricity anyway, meaning more heat per watt.

Daniel

 

[yellow]

a normal star alone is not enough.

Place it on some alum disc - 3 mm in thickness at least - that gets a press fit (screw in) into the body.

 

[JimmerG]

Yellow - you say apress fit/screw in - would this be in order to get a good contact with the torch body to help dissapate the heat?

I'm wondering if I make a disk that is as tight a fit as possible, and thermal glue it in place, so there's as much contact as possible - then thermal glue the star to the disk... would that do the job?

I haven't got the gear to start cutting threads in things!

Thanks

J

 

[yellow]

totally ok,
a tight fit + some thermal grease / thermal glue and press / glue that thing in

but I would screw the star to that "mounting plate" (+ add some thermal grease on the back).
That way You can easily upgrade to any new emitter with Star base