These details copied here with the kind permission of the original author

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2 x P7 LEDs= £30
2 x Circuit board = £8
1 x Battery = £10
3 x Heatsinks = £6
1 x switch = £4
Blob of thermal epoxy = ~50p

Total = £58.50ish (for ~1500 lumens!)


Hi Ian,
The heatsink is 3 x 1.25GY Heatsink (RS Stock No. 507-5835). Two of them are built back-to-back creating a cavity inside for the 2 circuit drivers.
The drivers i used are no longer available, however there are many now online, such as www.kaidomain.com/ProductDetails.aspx?ProductId=5486. Same physical size as the one i used so "should" be able to fit two inside. Kicks out 2.8A per LED.
I source my P7s from DealExtreme www.dealextreme.com/details.dx/sku.11809
The battery is a li-ion 3.7v 4800mAh cell from Battery Space www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2013 It comes with circuit protection which is reassuring.
Switch is just a simple toggle ON-OFF switch from RS.
I used Arctic Silver thermal adhesive to join the heatsinks and also the LEDs. I then coated the solder joints, misc holes, and the switch with normal surface adhesive, just to make it a bit more waterproof and hold it firmly together. Ideally it should have a clear plastic front and a plastidip battery, but i'm too lazy for now...
It didn't take long at all to assemble, suprisingly easy in fact!
Hope this is useful.
Rob

I've had a dabble with the P7's, originally I purchased a driver from kaidomain as well (being too lazy to build my own at the time) and it wasn't very good, bad regulation, and different drive currents for different input voltages.

Anyway ended up designing a simple constant current driver matched for 4 x AA NiMH 2.7Ahr batteries, with the overall battery voltage being close to the P7's forward voltage the power loss in a linear current regulator was not bad and acceptable. I added a microcontroller to give it 4 power level modes that it remembers. Packaged in a small Pelicase.

One of these has basically replaced my 50W defused halogen lamp.

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I'm also building another in a turned ali cylinder case with reflector for a power beam! Fully water proof to IP68. Will post it when done.

By the way if anyone is thinking of playing around with the P7's, I strongly recommend that you get a little ali PCB to mount them on to, which then can easily be moved from project to project. Or you can buy a P7 already mounted on one (best bet), then you only need to use a heat sink transfer compound instead of glue.

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Hi Mike
Hope you are well.
Re your posting.
A lot of the feedback on the DX website relative to P7s describes using multiple drivers boards from DX wired in parallel, admittedly cheap, to make up the 2.8 amps required to drive the beast. Well these boards at the higher voltages only run about 85% efficiency, so multiply by 3 and 45% of the battery power goes the same way as shares in Northern Rock.
Still using your Retro 2, good as gold, no problems.

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