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Discussion Starter · #1 ·
Hello,

I just received my two SSC P4 LEDs. One's about to go in my Cateye EL-530 tonight. The other one is now going in a Brunton Glorb camping lantern:

http://www.brunton.com/product.php?id=304

I unsoldered the LED from the Glorb (who comes up with these names?) and then took a voltage measurement across the two open contacts. I get 6.0V. (This lantern takes 4 X 1.5V AA cells). The specs on the SSC P4 say max voltage is 3.8V, so obviously I'm looking for a way to drop this down to 3.8V while sustaining max current.

Possible options:
The driver board is about 1.125 inches in diameter, but it's shaped like a "D" to fit in a holding ring that contains an ON/OFF push button. Therefore, I'm not sure that swapping the driver board is viable.....or is it?

Another thought was to add a resistor in series or parallel with the P4, but I'm not sure of the part value or it's effect on reducing current to the P4.

The other thought was to look around to see if there's a 6V to 3.8V voltage regulator out there.

BTW, the Glorb has a good size aluminum heatsink, so keeping the P4 cool shouldn't be a problem once I add a little more thermal paste.

Anyhow, if anyone has any suggestions, please let me know.

Thanks,
Keven
 

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There a two regulators that I know of and have used. Both from www.dealextreme.com. The first is the AMC7135 type regulator such as the SKU 1885 which puts out 1 amp. You will need a good heat sink for this current drain. There are other AMC7135 regulators with less output, Matter a fact, you have to jumper the above regulator to get that current. Each chip on the ckt board output about 350ma, so as is, it only will give you 350 ma.
The other regulator is the SKU 4255 (dealextreme.com) which is rated for 3-6.5v input with 700-800ma output, but I measure only 550ma. All these regulators are so cheap (from Hong Kong) that ordering a bunch of different kinds is the way to go. I have used these regulators in my bike light projects. SKU 1885 in Prototype 4 and SKU 4255 in Prototype 3. Both are powered by a 6 v lantern battery or 4 AA NiMH batteries.
http://www.kayakaccessri.info/krabachwebsite/bike_light/bike_light_project/intro.html
Be sure to bond the LED to the heatsink if you are not using a star base. Drawing 1 amp will really build up the heat fast. Unless the Brunton Glorb has aluminum from the LED to the outer surface of the lamp, you might be better limiting the current to 500 ma.
 
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Just a thought but is there room in the Glorb (nice lamp BTW)to rearrange the batteries so that you have two pairs in parallel instead of all four inseries. This will however only give 3 volts so not perfect. Or squeeze in a single 18650 cell @3.7v very cheap from Dealextreme.
 

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kev1024 said:
I unsoldered the LED from the Glorb (who comes up with these names?) and then took a voltage measurement across the two open contacts. I get 6.0V.
Put the original LED back and measure the voltage again.
The driver might be boosting the voltage trying to get the current to flow (which it wont without an led in there).
 
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znomit said:
Put the original LED back and measure the voltage again.
The driver might be boosting the voltage trying to get the current to flow (which it wont without an led in there).[/quote
Thats a good point. Do you know what the old led is as I can't think of one that would require 6volts.
 

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Discussion Starter · #7 ·
Everything is working fine....

Dom,

Yes, I have the same light as you've pointed out in the link. Very nice info on doing the mod and the images are great. Thanks.

As it turns out, I put the Glorb project on hold, waiting for an answer on stepping the voltage down and then proceeded to work on my Cateye EL530. After opening the Cateye, I took a voltage measurement and got 6V. No surprise...4 X 1.5V AA cells, just like the Glorb. Per instructions on this board, I proceeded to swap the stock LED for a SSC P4 and it works fine. So I went back to my Glorb and swapped its stock LED for a SSC P4 and it's cool too.

As others have mentioned here, 6V pushes enough current to get the LED to glow, so no need to step down to 3.7V.

Today I'll trim the Glorb's tailcap to keep from cutting the battery wrappers. And after SuperGluing the Cateye back together and sitting overnight, I noticed no matting of the optics this morning. As suggested here, I did let the glue dry a bit before reassembly.

Obviously, the Glorb and the Cateye are much brighter now. Can't wait for sunset to take the Cateye on a night ride.

Thanks,
Keven
 

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Like it was said above, you will only see 6V with the LED removed . With the LED in circuit you should see around the needed 3.7V. These regulators are current sources, not voltage sources. They force a constant current and voltage will rise or fall depending on the impedance in the circuit according to Ohm's law. When your circuit was open (LED removed) the voltage continued to rise until it reaches the maximum limit of the power source, giving you the 6V you measured.

The point is, your lights are fine.
 

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Discussion Starter · #11 ·
No need to cut off the top...

Dom,

Thanks for the tip on rechargable cells being "fatter". That explains why my alkalines seem to be OK.

RE: modifying to Glorb - I found that it wasn't necessary to cut off the top cover, which eventually forces you to glue it back. All I did was remove the 3 screws in the battery compartment. They screw into the diffuser, which anchors the top half to the bottom half of the lantern. It's a little tricky, but it works.

Keven
 
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