DIY LED lamp

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gbb

Legendary Member
Location
Peterborough
Let me run this by you...
One of the things that bugs me with DIY lights is you invariably have to have the batteries mounted somewhere else. Going to try a project that will incorporate the batteries in the lamp itself.
Initially i'm going to use
ABS box, 100x50x40
A single Cree MC-E Star that gives a whopping 430 lumen :evil: Vf is 3.2
A 700ma driver
2.2Ah 7.5 volt Li-ion battery.

I can just fit (i hope) it all in the box.

The question is, i want to charge the battery while its in the case...will this diagram work ?
ledcircuit.jpg


It aint going to be cheap...the Cree star alone is £20 plus

Any thoughts ?
 

Joe24

More serious cyclist than Bonj
Location
Nottingham
Could i fit a Cree thingy into a dynamo light?
Sorry, dont mean to hijack the thread, but is there any light thats hugely bright, and runs on 6v?
Just as a bit of a question to you GBB
 
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gbb

gbb

Legendary Member
Location
Peterborough
Joe24 said:
Could i fit a Cree thingy into a dynamo light?
Sorry, dont mean to hijack the thread, but is there any light thats hugely bright, and runs on 6v?
Just as a bit of a question to you GBB

Hi joe
It all depends on whether you can somehow mount the LED, heatsink and driver in the housing you already have...its fixing it all in securely thats difficult. It can be done, but it depends on the housing obviously.

6v isnt a problem..most LEDs have a Vf of 3.2 volts, so anything above will run the LED through a driver.
A single 'normal' Cree runs at about 60 to 100 lumens. Thats bright...but not hugely so, thats why you often see double or triple Cree setups, to get more light output. (Thats why i want to try this mother...keep it compact but with high light output.)
You're only going to be able to run a single LED with 6v though...two LEDs will require a minimum of 6.5v plus.
Then...will you run it off the dynamo ?....the circuitry works differently for a dynamo. I dont have any experience with them
 

02GF74

Über Member
that circuit disagram is good - I would look at the DC connector socket to be a "make before break" or whtever that has a contact to disconnect to the driver side - you don't want to be charging the battery with the LED on although you will know if you are going that and can use the switch to turn it off.

430 lumens @ 700 mA - you sure that is correct?

I am using seoul P4 star emitter, spc., sheet says 100 lumens @ 1.4 A!!!


Have you got the driver yet? I have some 3 W drivers that are no use to me - would save you a bit in postage to China or whereever.

See my post on DIY lamps.
 

02GF74

Über Member
gbb said:
Hi joe


6v isnt a problem..most LEDs have a Vf of 3.2 volts, so anything above will run the LED through a driver.
A single 'normal' Cree runs at about 60 to 100 lumens. Thats bright...but not hugely so, thats why you often see double or triple Cree setups, to get more light output. (Thats why i want to try this mother...keep it compact but with high light output.)
You're only going to be able to run a single LED with 6v though...two LEDs will require a minimum of 6.5v plus.
Then...will you run it off the dynamo ?....the circuitry works differently for a dynamo. I dont have any experience with them

most drivers need a headroom of at least 2 volts above the lLED Vfd so you are looking at 5.5 V minimum.

I am pretty sure dynamos produce AC voltage so you would need a rectifier and a capacitor for smoothing.

You need to buy a lens to focus the LED light and the lens on your dynamo may mess the beam pattern.

I think it is doable. You can ofcourse ditch the dynamo headlamp and make one as described in my write up - do search for DIY LED lamps.
 
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gbb

gbb

Legendary Member
Location
Peterborough
I can already see i'm missing something...
The MC-E had 4 seperate dies in one LED, each with a Vf of 3.4v at 700ma, so my 7.5v battery is no good. You need something like 14volts and a bit

02GF74...
I'd already figured the switch would be 'off' when charging, that'd disconnect the driver from charging circuit. Good point about the 'make before break socket', but i'm just using bits i've already got.

430lumens....its a bit confusing when you read their data sheets...
they quote 430 lumens at 350ma at each die (there are 4 dies per LED package)..maximum permissible 700ma.

My driver is a board mount version i just happen to have access to.

I'm at the early planning stage, so i think i may be re-considering my options.
 
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gbb

gbb

Legendary Member
Location
Peterborough
gbb said:
I can already see i'm missing something...
The MC-E had 4 seperate dies in one LED, each with a Vf of 3.4v at 700ma, so my 7.5v battery is no good. You need something like 14volts and a bit


02GF74...
I'd already figured the switch would be 'off' when charging, that'd disconnect the driver from charging circuit. Good point about the 'make before break socket', but i'm just using bits i've already got.

430lumens....its a bit confusing when you read their data sheets...
they quote 430 lumens at 350ma at each die (there are 4 dies per LED package)..maximum permissible 700ma.

My driver is a board mount version i just happen to have access to.

I'm at the early planning stage, so i think i may be re-considering my options.


Ref the above...i see each die is 'wired' seperately on the MC-E, you can use 1, 2,3 or all of the individual dies...i'm going to do some homework and see what output i'd get if i just used two of the dies.
 

jimboalee

New Member
Location
Solihull
I did some prelim' experiments last year with a Sturmey Dynohub, Full wave diode bridge, Tesco 3W torch and a Ring 5W cybalite.

The Tesco torch worked fine.

The 5W Cybalite didn't give a glimmer.

Gave up on the idea. Run both torches on rechargables.
The extra weight of a dynohub swayed my decision.
 

02GF74

Über Member
gbb said:
I can already see i'm missing something...
The MC-E had 4 seperate dies in one LED, each with a Vf of 3.4v at 700ma, so my 7.5v battery is no good. You need something like 14volts and a bit

yeah, I did wonder about that. if the LEDs are well matched, you could run them in parallel but there is the danger of current hogging and blowing them up.

you'e be looking for at least 16 V, the driver needs a couple of volts headroom ... or use a separate driver for each die.

make sure you have good heatsinking - they get pretty hot!!
 
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