P7 Helmet Completed - Help with tweaks

atx · Sep 17, 2008

I finished a P7 MiniMag Mod for my bike helmet. I have two problems:

1) It runs very hot. The cavety behind the sink is filled with paste, and the heat is being transfered to the outer casing, but still very hot. Too hot to touch. Would switching from direct drive to a fix-current circuit of some sort help - prob. not without limiting the brightness.

2) I'm using the stock reflector (modifiied) which is too wide. Any suggestions on a drop in reflector for a P7 mini mag?

Pictures:

StevelKnievel · Sep 17, 2008

I don't think you'll be able to dissipate enough heat into the air with your current setup without significantly reducing output. A constant-current driver isn't going to help, you need much more mass and surface area or else :poof:

!!! You'd be better off putting an under-driven single die emitter in this host and building something else capable of handling 10+ watts. FWIW it looks like a clean bulid...

greenLED · Sep 17, 2008

Finning the head will increase dissipating surface area.

Also, attach the light to the outside of your helmet for increased air flow (every bit helps!)

Also, too much thermal paste will actually isolate heat.

You want to get as much surface contact between the heatsink, the head, and the tailcap. I mention this because I'm not sure how the tailcap is pressed against the head.

Other than that, I really like your setup! Are you DD'ing the P7?

Pics of the internals, please?

Meltdown · Sep 17, 2008

try only cycling in the rain

looks nice BTW. i think I'll try my hand at a P7 bike light soon.

f22shift · Sep 18, 2008

run 3 alkalines rather than nimhs?

maybe get some metal(copper) strips to mount. too dangerous maybe.

throw in a d2dim in there so you can adjust output?

i wish someone made a heatsink for the minimag. a dd minimag 3aa would be fun for short bursts

Gunner12 · Sep 18, 2008

The AA minimag head doesn't have much metal to absorb the heat. Also Thermal paste/epoxy isn't that good at transferring heat when used in large amounts.

Make the light stick out more and fin the head so it can cool faster.

As for a reflector, I heard the McR-20 fits the Minimag. I don't know how much it would help though.

greenLED · Sep 19, 2008

Gunner12 said:
The AA minimag head doesn't have much metal to absorb the heat. Also Thermal paste/epoxy isn't that good at transferring heat when used in large amounts.

Make the light stick out more and fin the head so it can cool faster.

As for a reflector, I heard the McR-20 fits the Minimag. I don't know how much it would help though.

Sounds like we agree on all accounts.

Yes, the McR20 fits inside the minimag head, but you need to open the OD of the top end of the head. In terms of heat management, I'm not sure it'll help dissipate any of it. If anything, it won't melt/warp with a lot of heat like the stock reflector will.

donghui · Sep 21, 2008

Still don't think the mini mag is the right candidate for a p7 mod it's just too tiny. I think the best way to improve the heat management is to drill some holes or dremel some fins on your mini mag, make it better to air cool when you are riding.

atx · Sep 21, 2008

Plan Adjustment

My current plan is to build two, each with multi mode driver, a little longer tailcap, and a proper copper heatsink, rather than all the paste. Then mount them on the helmet for maximum airflow, and I can alternate between the two as I ride, turning one of them to low or off periodically for cooling. That way I can keep the small package size, and have a very bright dual beam for short bursts.

I might burn them both up, but we'll see. I'll let you know how it goes.

f22shift · Sep 21, 2008

how's the beamshot?

Bobpuvel · Sep 21, 2008

That looks really cool!! but sadly I'm a noob and can't help with the problems...

P7 Helmet Completed - Help with tweaks

atx

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StevelKnievel

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greenLED

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Meltdown

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f22shift

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Gunner12

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greenLED

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donghui

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atx

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