Before I purchase...

[kuksul08]

Does this look like it'll work?

The only questions I have are regarding what size potentiometer to buy. I went to the store and they have anywhere from 500-50k ranges, and wire wound/cerment varieties.

Also regarding forward LED voltages. I have an SSC P4 in a headlamp and when running at 330mA its Vf is 3.02V. Isn't that kinda low?


Thanks

 

[Black Rose]

The forward voltage of the SSC P4 depends on which bin you have.

I believe most are in the 3.0 - 3.25v range, but there are some that are in the 3.25 - 3.5v range.

 

[kuksul08]

It's one of these http://www.dealextreme.com/details.dx/sku.1445

 

[Black Rose]

I have some of those as bare emitters.

The spec sheet says the vf is minimum 2.9v, typical 3.25v, and maximum 3.8v

 

[kuksul08]

Hmm, so it's kinda hard to tell exactly then.


How about my other question?

Also what size wire should I use? I was thinking 20Ga stranded to be safe.

 

[Black Rose]

Not sure about the potentiometer. I just use resistors for the stuff I build with 5mm LEDs.

I bought 24 guage stranded wire for my projects.
But now I need to get a new wire stripper since mine can't deal with 24 guage and using an X-acto knife is a pain.

 

[kuksul08]

Thanks for the help

It's pretty confusing. Maybe I will first just buy a few parts to play around with before spending more money on a big project

 

[kuksul08]

Couple more questions...

My goal is to build a bike light that I can attach to my helmet or handlebar. For now I will be using two LEDs in a custom aluminum enclosure. I was planning on using P4's, but would the cree XR-E Q5's be a better choice? I don't know much about them.


I will be using this homemade circuit

from this instructable: http://www.instructables.com/id/E7QH8NG8I1EWOF32HJ/

I think I will run them at 700mA but I'll see how hot they get.

I just don't want to mess up here

 

[kuksul08]

Well crap... I went out and bought the parts to make the driver and it burned out my LED. With a 4.8V input it put out 1A, and with 7.2V input it put out 5 amps! I should have checked it first... the led turned blue and went out pretty quick.

Guess I'll just have to buy some DX or buckpuck driver now...

 

[Black Rose]

Your first diagram shows the AMC7135 driver.

Were you using that, or is that a driver you had planned on getting from DX?

 

[kuksul08]

The first diagram was my original plan. I then made my own driver using the second schematic, and as it turns out I wired it wrong. Once I switched one connection it gave exactly the current I specified. doh!

 

[elnero55]

darling pair?

what kind of batteries do you want to run this off?

 

[kuksul08]

darling pair?

what kind of batteries do you want to run this off?

6AA NiMh's