Diamond DB-K2 impression

[evan9162]

K2 4.55 volts, 675-680 Ma. which surprisingly is only 3.09watts. (so much for the 6.5 watt claims) Current rises slowly as temp goes up.

That tells me that the diamond is simply using a resistor to limit current. The Vf of an LED has an inverse temperature coefficient, meaning as the temperature of the LED rises, the Vf drops (temporarily). A lower Vf = higher current. The diamond drop-in is a prime candidate to destroy an LED via thermal runaway. Things are bad enough since they are driving at only 700mA - the K2 wouldn't last very long if they decided to run it at 1.5A.

While the mag drop-in doesn't have very good thermal paths, it at least throttles back the current to prevent damage to the LED. Unfortunately, the diamond drop-ins simply run the LED balls-to-the-wall without any real consideration for thermal management. Sure, they have a big chunk of aluminium which is nice for using the light 30 seconds at a time, but once you have the light on for a few minutes, it's just as if there were no heat sink at all.

 

[DShealey]

I took some pictures comparing the MagLed and K2, but unlike another forum I am on that uses Vbulletin I cannot upload them here to insert them.


The MagLed is definitely a better upgrade to me. Throw to the house across the street at night (about 150 feet) is MUCH better, even when the lights have been on for over 30 minutes and the MagLed internally throttled way back, approximately 1/2 the current of the K2.

That means that anyone using these in lights that may be needed in an emergency can expect MUCH longer battery life with the MagLed, with negligable loss of light compared to the K2!

I found another small issue with the K2: I switched heads on the lights to be sure the spot shape differences were not related to the reflector, and one of the lights would not focus with the K2. Tried a third light and it worked. The K2 is slightly larger in diameter than the MagLite bulb retaining nut, and this small difference was enough to prevent it from protruding through the hole in the lens. It would be a pretty easy fix, only a few thosandths of an inch, but it can be an issue.

 

[cavanaug]

I received my 3-cell K2 a couple days ago and finally bought a 3D Mag last night to put it in. I will have to agree almost completely with what Yaesumofo has posted. My K2 is very white and bright. If anything there might be a very slight hint of pink, or just a slight warmth to the color.
I applied a little ProGold to the threads and electrical interfaces before I screwed the heatsink onto the flashlight. I measured the current with my DVM this morning (10A scale) and it consistantly measured an unbelievable 678mA. Hopefully someone else can do a measurement, because this seems way too low for all the light it produces. This meter has been very accurate on other lights so ???????
I do think I will lightly sputter the reflector to see if it smoothes out the beam a little. It's not bad, this thing kicks out a lot of usable light. I just want a little impovement when looking at walls, I know most CPF'ers understand that. I did have an extra UCL lens, so I installed that when I installed the K2.
So far, with only limited use, I am impressed with this inexpensive, easy to install, mod.

Just out of curiousity how do you measure the current on the bulb?? Ive got a DMM somewhere around here and I wanted to understand how CPF'ers measure the current of their bulbs.

--
John

 

[Navistar]

Mine was DOA right out of the package this is the 2nd time this has happened with this company.Guess I'll have to send it back I'm

 

[yaesumofo]

Some people take the tail cap off the light and place the DMM in line measuring the current draw from the body to the negative side of the batteries.
When I did it this way my reading was in the 600 Mah area.
I have no idea whether or not this is the best way to do this.
I have a feeling that taking a measurement from the positive side of the switch to the emitter may be a more accurate way to do this.
The best way to measure the current draw would be to use a power supply set to the correct voltage 4.5 V and measure the current draw from the supply to the globe. This is an accurate way because the voltage will not drop even after a few minutes of on time which happens on batteries.
I have the tools but lack the time at the moment to set up this experiment.
I am sure somebody will get to it.
Yaesumofo

Just out of curiousity how do you measure the current on the bulb?? Ive got a DMM somewhere around here and I wanted to understand how CPF'ers measure the current of their bulbs.

--
John

 

[IsaacHayes]

Measuring from tailcap lets you know how much draw is from the batteries.

To find out current to led, you must have the DMM inline with a wire going to the lead of the luxeon. that means disconnecting a wire. This will tell you true current through led.

If it has a driver then we can only approximate current to the led from the tailcap measurement.

 

[DShealey]

Just out of curiousity how do you measure the current on the bulb?? Ive got a DMM somewhere around here and I wanted to understand how CPF'ers measure the current of their bulbs.

--
John

It is easy to measure the current, just take the back cap off the light, and use a multimeter with a suitable current range. Measure the current from the bottom of the battery to the light case when the light is turned on.

 

[DShealey]

Some people take the tail cap off the light and place the DMM in line measuring the current draw from the body to the negative side of the batteries.
When I did it this way my reading was in the 600 Mah area.
I have no idea whether or not this is the best way to do this.
I have a feeling that taking a measurement from the positive side of the switch to the emitter may be a more accurate way to do this.
The best way to measure the current draw would be to use a power supply set to the correct voltage 4.5 V and measure the current draw from the supply to the globe. This is an accurate way because the voltage will not drop even after a few minutes of on time which happens on batteries.
I have the tools but lack the time at the moment to set up this experiment.
I am sure somebody will get to it.
Yaesumofo

The current is measured just fine that way. Current will be the same anywhere in the circuit. Voltage however can be measured at various points in any circuit.

When I did my brief testing, the current was measured with the tail cap removed. I soldered a small wire to the positive terminal of the top battery and ran it past the batteries and out the tail cap to measure the battery voltage supply under load.

Tonight I measured the voltage at the LED itself, and got 3.76 volts, which at the measured 680 Ma is only 2.56 watts!!!

I had assumed when I ordered these "6.5 watt" K2s that in the flashlights they would probably run somewhere in the 4-5 watt range. Surprise!

I just measured resistance from the bulb contacts to the LED and see that there is a 0.4 ohm resistor in series with the bulb.

These things are WAY off the specs on the Diamond packaging. BAD DOG!:thumbsdow

 

[DShealey]

Measuring from tailcap lets you know how much draw is from the batteries.

To find out current to led, you must have the DMM inline with a wire going to the lead of the luxeon. that means disconnecting a wire. This will tell you true current through led.

If it has a driver then we can only approximate current to the led from the tailcap measurement.

The K2s seem to only have a 0.4 ohm resistor in them, no driver. Without active circuitry, current can be measured anywhere in the circuit, as it will be the same at any point. Voltage will be different at various points, but not current.

 

[yaesumofo]

No driver. these are direct drive.
In any event mine is Bright. Just as bright as several of my top LUX III Space needle mods.
The only real problem with these things is the fact that there is not enough heat sinkng. The average user on the street will never notice this. The package says 6.5 watts. Based on current and voltage measurements made by myself and others it is clear that this number is inflated.
It is still bright.
When you buy a BOSE system you will notice that they do not publish a complete spec. They say " listen to it, How does it sound?" Many people like the BOSE sound (NOT ME). The same could be said of these little thingys. Stick it in. Turn it on. It is bright.
Brightness is the basic goal of this mod. The DB-K2 delivers.
Yaesumofo

Current measurement would be a better indication too of what it's pulling and what kind of driver it may have.

 

[DShealey]

-------------------------------
Brightness is the basic goal of this mod. The DB-K2 delivers.
Yaesumofo

I agree. But for me, the MagLed drop ins deliver better than the K2. Better spot consistency and focus to a tighter spot, which appears brighter than the K2, even after 30 40 minutes run time the smaller spot of the MagLed appears brighter than the K2, while pulling less than half the amperage from the batteries.

Even after the MagLed has dropped to half the current of the K2 due to the temperature regulating driver in the MagLed, when focused out to the same size as the K2 focused as tight as it will go, there is only a small difference in the brightness. With the MUCH better battery life, and almost equal brightness with better spot shape, I will take the MagLed.

Trying to return four Diamond K2s so I can just buy four more MagLeds, but so far they are not communicating. Tried fax and email, no one answers the phone. Must be on vacation or something.

 

[dwminer]

I have been trying to get the company refund the charges on my credit card with no luck so far. Called again this morning and left another message. At this point I just want my money back.
Dave

Update: They called back and said that the order had been cancelled, but the warehouse in LA had not credited my account. They said that a credit will be issued today. I will follow this up.

Update, Update: 16/06/06 all is well now, credit had been received.

 

[evan9162]

Dispute the charge with your CC company. That will get Diamond's attention REAL quick.

 

[IsaacHayes]

Reminds me of an order gone wrong w/future once I had. After it was straightened out and they send me the right parts, they charged me for the new ones. I had to call them up again and tell them that I was not credited back for the wrong parts. Finally they talked to their accounting and had it credited. They still charged me shipping for the new parts though, even though they messed up. The told me not to return the wrong parts, but just to trash them. I kept them so I ended up coming out even or a little better.