circuit board

[jasonsmaglites]

ok. what exactally is this and why would i want it in my next build? dx skew 1886

http://www.dealextreme.com/details.dx/sku.1886

there are 1050 ma and 1400 mah drivers, and i'm trying to understand how to wire them, and how to allow for varying voltages. for instance, can i hook a 6d up to this as well as i could a 4d? and when i use these, do i get lower overall efficency than if i was direct driving something, for instance my next 4d mag p7. how do i allow myself to drive a p7 off of higher voltage configuations if this isnt the key

 

[Lumencraft (Matt)]

Hi jason,

You are on the right track, but for a simple p7 mod I would recommend a different driver. The specs on the driver you posted say 3.7-4.5 volt input voltage is recommended. So either one li-ion or 3 nimh would probably be best. If you are looking to go cheap KD has this driver, I use one of these in my p7 mag, but it will need to be heat sinked. This is what is known as a "Buck converter" The input voltage range for this is 5.5-15v (although anything above about 8.4 makes it get hot very fast) so you could use this in your 4-6 D. If you decide to go with this driver I can post some pics on how to wire it.

 

[VegasF6]

ok. what exactally is this and why would i want it in my next build? dx skew 1886

http://www.dealextreme.com/details.dx/sku.1886

there are 1050 ma and 1400 mah drivers, and i'm trying to understand how to wire them, and how to allow for varying voltages. for instance, can i hook a 6d up to this as well as i could a 4d? and when i use these, do i get lower overall efficency than if i was direct driving something, for instance my next 4d mag p7. how do i allow myself to drive a p7 off of higher voltage configuations if this isnt the key

You have just discovered a linear driver, or what amounts to a variable resistor. There is quite a bit of discussion about them here actually, search for 7135. Max input voltage is ~5 volts or so. Any excess voltage is burned off as heat, when your led VF matches your battery voltage, they are 100% efficient, or nearly so. But, only for a very brief time.

Each 7135 limits current to about 350 mA. So, they are wired in parallel to achieve higher currents, IE 2-4 on a board. In addition, multiple boards can be paralleled for even higher currents.

Netkidz thread has a great tutorial on how to wire them.
http://www.candlepowerforums.com/vb/showthread.php?t=192677

In addition, this thread by download http://www.candlepowerforums.com/vb/showthread.php?t=201392 shows an innovative way to get around the input limit with multiple emitters.

Direct driving, if it can be done without burning up something, is the most efficient way to drive a led as 100% of your battery power is going to driving the led (minus any losses for resistance in your circuit that is)

As for other ways to drive a P7 from higher voltages, you will need a buck regulator. You can look at the Der Wichel regulator, which I believe is actually a voltage regulator. The Shark Buck from the sandwhich shoppe is a switch mode buck regulator. There is an option from KD which IIRC has over heating problems, and there is a new option from DX that has only been listed for a day or two, so no one knows much about that yet.

I believe George at taskled has a high current driver in the works as well. Your quality drivers will probably be priced over 25$.

 

[jasonsmaglites]

ok, what is the d2flex that i hear people are starting to make their heatsinks around? meaning the led goes on top and this circuit fits snugly in the bottom to drive the led. also, could someone give me the basic rundown on what the drivers do. is that the same as a circuit board. when do they become efficent like a fenix, and why do some use pwm vs "variable resistor" like just mentioned. how do they allow a aa to drive a 3.6 volt led, and when they do that, does it cost you energy? how about when they're stepping down voltage? is that any less efficent?

 

[VegasF6]

This would require a rather long answer. I am thinking you need to do some searching about drivers.

Try this thread http://www.candlepowerforums.com/vb/showthread.php?t=201375 There is a driver section a little ways down. Also try the stickies at the top.

It is going to be rather hard to explain everything possible about drivers in one thread, but if you have a specific question or two, ask them.

For instance, the D2dim and its sucessor (sp?) are PWM (pulse width modulation) boards to allow dimming, for different modes. But, they don't limit current or step up or step down voltage.
http://www.taskled.com/d2flex.html
Have a look around the taskled board at the products and technical page to get a better idea of what they do.

P.S. the main reason for the linear regulator is cost and less components on board (simplicity). And step down boards (buck) are usually more efficient, but it depends on the quality of the design. Choosing proper components and also proper layout of the components to achieve high efficiency is an art, one beyond me.

 

[jasonsmaglites]

good link. so a convertor (buck or boost or both) is for getting proper voltage to the vf of the led but will basicly direct drive the led, regulated in the sense that whatever the voltage output of the convertor is set to, the led will get. since led's draw amperage based on what voltage is being fed, its left to the led what amperage to pull.

however a circuit board, single or multi mode, is for limiting current, or amperage. if for instance i wire my p7 with 2 1400 mah circuit boards, its gonna get 2800mah, no matter the relative vf of the led. the led will be getting whatever voltage it needs to match that current.

sound right or flawed?

 

[LED_astray]

Not strictly right. It's hard to tell if it's a useful approximation for you, but I'm afraid it could mislead others.

First, you can't think of a driver or a LED in isolation. They affect each other's behavior and it is the full circuit that is balanced. I've tried to explain before, e.g:

http://www.candlepowerforums.com/vb/showpost.php?p=2822987&postcount=7

http://www.candlepowerforums.com/vb/showpost.php?p=2720613&postcount=9

maybe those will help. Or search around, others have also explained it and maybe they used words that you related to better.

In the examples I always use a resistor as an example "driver" because it is simple and easy to understand. In this case you're talking about an active driver circuit that will react to the LED. For a driver designed to provide a regulated current it will set the voltage to whatever the LED requires at the specified current. So, e.g. a 350mA driver might drive 3.5V for one LED and 4.1V for another. If the driver is designed to regulate voltage, then yes, the LED will set the current. Generally light from an LED is proportional to the current, not voltage, and current regulators are preferred. (BTW- a circuit board just holds a circuit. The circuit can be a regulated driver, a switch, or the electronics in your computer.)

(And of course all this only applies within the driver's design limits. E.g. get the input voltage too high, or too low, and it won't work as designed. What it does can be defined and graceful or very unfortunate.)