Favourlight LTC-1613AA Locator LED Mod

[dchao]

I recently received the warm white version of the Favourlight lantern. One of the nice features on the lantern is the locator light. When the lantern is off, the locator LED flashes once every three seconds. However, the light is very dim and the LED recessed all the way inside the body.

So I decided to replace the resistor on this LED to make it brighter.

There are four tiny screws in the battery compartment that hold the body and lens down to the electronics inside. Remove the screws, the body will slide off and you can see the guts inside.


(R7 resistor already removed)

The resistor that controls the current to the locator LED is labelled R7, and the factory installed value is 3.9K, which will give a current to the LED :

(Regulated Voltage - Vf) / Resistor = (5-3.2) / 3900 = 0.5mA

I want to get the max current allowed (20mA) to the LED , therefore, I am going to replace the factory resistor with a 82 Ohm one.

Remove R7 resistor with a small soldering iron tip, clean up the pads with solder wick. Finally, solder a new 82 Ohm resistor on. Assemble the lantern. And you are done.

This mod should be applicable for all versions of the LTC-1613AA Favourlight Lantern, since the only difference to the warm white version is the Cree LED.

 

[LEDAdd1ct]

Very cool! How will this mod affect the battery life going from 0.5mA to .20mA?

 

[dchao]

It's a bit hard to do a run time test on this lantern, since I love this light, and I just can't resist to turn it on and play with it :D

We don't have any info on the chip-on-board IC (The IC under that black glob). Therefore we have to make some assumptions, base on a similar charge-pump driver, the Linear's LTC3220, the shutdown current is 4uA. And we know the blink duration is 0.1s, and the flashing period is 5 sec.

If we increase the green LED current from 0.5mA (with 3.9K resistor) to 18mA (with 82 Ohm resistor). With 4uA standby current. The brighter LED is going to take 26x more power than the factory one. This is a very quick estimate.

On Favourlight's packaging,it say the green LED mode will last 2 years. So if you take the current to 18mA, it will shorten the runtime to 28 days. About one month.

Of course, one can choose any resistor value from 82 Ohm to 3.9K Ohm to suit their own needs.

 

[dchao]

A few small changes to my locator LED setup.

Got some brighter diffused 3mm red LED's from eBay. They are rated at 3000mcd, and has a Vf of 2.0V @ 20mA. And replaced the stock green LED.



I also increased the current limiting resistor to the LED to 270 Ohm. With 3 x NiMH cells at 1.35 x 3 = 4.0V. The current going to the LED is:

(4.0V - 2.0V) / 270 Ohm = 7mA

I think this setup should make the lantern last much longer with just the locator LED blinking.

Finally, I did not like the lens for the locator LED buried so deep behind the aluminum body. So I used some Norland 61 epoxy to build another lens to cover the LED hole on the aluminium body. I taped the hole from inside and then poured some epoxy into the hole. I made sure I poured a bit more epoxy into the hole, so the lens bulged outward - a convex lens. I let the epoxy dry in the sun (UV curing) for a few hours, and then removed the tape.

Final result here, not a great picture, but the lens is just visible: