My bike shop wants me to build some lights.

[crackerkorean]

After seeing my light (with only two leds) the shop manager and shop owner wants me to build some lights for the team guys.

This is what they want and not sure exactly how to do this.
They want full on 1A power, no low med high.
But they do want a low voltage warning and if the voltage gets to low the light will automatically dim.

Any idea what driver would fit the bill?

 

[Szemhazai]

nflex / bflex in UIB2 version will be the best.

 

[chris_m]

Though the bFLex doesn't do auto dim on low battery.

 

[Szemhazai]

I doesn't but he can put to their heads - change the mode after red led starts shining

 

[crackerkorean]

Thats what I figured. I was just trying to keep the cost down. Just wasnt sure if there was a way for an LED to light when the battery hits a certain voltage using a boost or a buck puck.

MY second light will be what I would build for the shop so bflex UIB2 it is.

 

[iggs]

I thought with the bflex that as the battery voltage drops below the Vf of the led's the bflex ceases to work and then the lights will just dim as the batteries go flat slowly. Surely this effect will look like auto dimming

 

[tonycollinet]

My lights effectely auto dim on that principle.

I have 10NIMH cells (nominal 12V) driving 3 luxeon III (aprox 10V) through a constant current driver at 1A

As the battery voltage starts to droop below about 10.5V, the LEDs naturally dim. It is not possible to fully discharge the battery, because the LEDs will just take less and less current as the voltage drops.

I have left them on, and they are still lit (dimly, but probably still bright enough to use if you only need to be seen) after 15 hours. I would guess the current at that point is less than 100mA.

The trick is to have the nominal battery voltage only one or two volts higher than the LED voltage + the votage drop in your driver.