noob question Q5 driver

[csinsc]

Hi,

I bought the 3AA (4.5v) version of the Northern Tools led light... the light seems to be ideally suited for modding.

http://www.northerntool.com/webapp/...stomer driven-_-Recently Viewed-_-Search Page

I want to place a Cree Q5 star board in there but which driver should I use?

One other questions I have are:

The driver boards, when you use them with 2 cell batteries, do they bump up the voltage (i.e. to 3.7 volts for the leds)?

Or is the only requirement for the led to conduct simply the .7 volt break-over voltage?

I guess my questions are about what functions the drivers perform, voltage/current regulation?

Thanks,

Chris

 

[Gunner12]

A driver changes the input voltage and changes it to the voltage the LED needs.

With 3 AA batteries, the light probably has a resistor in there. If you want to use a driver, look at a buck driver(like this) if you want to use 3 AA batteries.This boost driver might also work but then it will be direct driving until the batteries get below the Vf of the LED.

If you use a D cell(a bit larger then 3 AA cells might fit), use this driver and also get 5 modes with your light. If you 3AA batteries, this driver will give more light and also 5 modes, or this one if you use rechargeable batteries(3 modes and brighter die to more current).

About how it works, all I can do is point you over to the Wikipedia link about voltage regulators and DC-DC converters.

 

[TorchBoy]

From various posts I've read, three cells might not give you enough volts for a Q5. Don't know what you mean by a 0.7V break-over voltage. All white LEDs need at least 3V to get any reasonable light out of them.

Do you already have a Q5, and if so, what operating voltage does it need for the current you want to run it at?

 

[Curious_character]

Hi,

I bought the 3AA (4.5v) version of the Northern Tools led light... the light seems to be ideally suited for modding.

http://www.northerntool.com/webapp/...stomer driven-_-Recently Viewed-_-Search Page

I want to place a Cree Q5 star board in there but which driver should I use?

One other questions I have are:

The driver boards, when you use them with 2 cell batteries, do they bump up the voltage (i.e. to 3.7 volts for the leds)?

They provide a constant current. The LED, not the supply, establishes the voltage. The driver does have to be capable of supplying the required current into an approximate 3.7 volt load.

Or is the only requirement for the led to conduct simply the .7 volt break-over voltage?

A silicon diode has a forward voltage of approximately 0.7 volt at moderate currents. LEDs are not silicon diodes; their forward voltage is much greater. You can find graphs of the voltage vs current of typical LEDs many places in the CPF archives. I posted one here.

I guess my questions are about what functions the drivers perform, voltage/current regulation?

Current regulation. See the second posting down from the link for a description of a current source.

c_c