Hi all,

I thought this was going to be so simple! And I guess if you knew where to look it would be, but I am struggling and hoping someone can help.

We have some of these LED hurricane lamps for when camping (see image attached) and they are ok, but they use the very cold white LEDs, which isn't really what you want at night camping, so I want to replace them with warm white LEDs. I really thought it would be a simple job, solder in some new bulbs and it would be done, but I am struggling to identify what ones I need and where to get them, plus I want to alter the lamp a bit.

The lamp uses two D batteries, in series, giving a voltage of 3v (the batteries are actually a bit old, so I am only getting 2.6v). This then goes through what looks to be a rheostat(?), and from here the voltage is around 1.5v. these are crap and the lights flicker and sometimes refuse to come on unless the switch is played with. So I am thinking of removing this and replacing with a simple on/off switch.

From here it goes to the circuit board, which holds the 15 LEDs in parallel. There is a resistor in the circuit, which is Orange Orange Black Silver, which I think is 33 ohms, although actually by multi meter reads it as 0.8ohms. There is also a transistor, which has YX8121 4]033 written on it.

Wow, that was long winded and I apologise. So what is going to be my best way of converting these to warmer LEDs?

Many thanks in advance,

James


Read more http://www.resistorguide.com/rheostat/

 

LEDs in series must have their forward voltages matched so that they are all the same. But they have a wide range of voltage when purchased.
In parallel, the LED with the lowest forward voltage takes all or most of the current then quickly burns out, followed by the next then the next.
So you must purchase many extra LEDs and test and sort them all.

Since the forward voltage of white LEDs is around 3.0V then calculation the value of a series current-limiting resistor is impossible. Maybe the transistor was in a current-limiting circuit but it would not have any voltage to do it. Maybe the transistor was in a voltage-boosting and current regulating circuit? Who knows.

My cheap Chinese flashlight has 24 white LEDs in series and their forward voltages are matched very well. The battery is three AAA cells and their internal resistance limits the total current. When I replaced the cheap weak "super heavy duty" Chinese cells with modern powerful Western cells then the LEDs almost burnt out so I needed to add a series current limiting resistor.

Maybe you should buy a cheap Chinese flashlight that already has its LEDs matched and use those LEDs in your lantern..

 

LED manufacturers often bin LEDs by voltage.

 

What you are attempting to do is extremely difficult, I would suggest a filter instead.

 

Many thanks for all your help so far.

What if I was to start from scratch and build a multi LED light, that fits in the base. That cannot be too difficult?

James

 

Should be much easier to build yourself. I bet you could even just google the schematic and follow it at the same time keeping the shape to fit in your lantern. Its very simple thing to do if you only care about adding lights and a on off switch.

http://led.linear1.org/led.wiz