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JLSE · Apr 7, 2008

Good idea, im going to try that. So far thats been the only thing missing (load). Can I use a 100 ohm multiturn pot set to 50ohm? I dont think I have any resitors of that value. The spike is brief, it only lasts for a second and then it rests at 6v.

phenol · Apr 7, 2008

50 ohms was a wild guess. of course you can use a pot. just start from its max resistance gradually going down and measure the voltage. alternatively, set ur meter to mA and connect it in series with the potentiometer. this way you are going to see if from a certain point on the current remains constant

JLSE · Apr 7, 2008

Okay, got a 47ohm resistor and placed it as a load and measured the voltage across as, 9v peak and 4v steady at 3v in with the pot set at 0 ohm. The current measured between the pot and the load was then set to 38.ma on the nose. When the power is cut and reconnected the current starts at 36.9ma and climbs to 38 and holds. So the current is good, just the voltage...

cheers.

Almost forgot! At 38ma the voltage spikes at 3v and drops to 1.6??? This cannot be a good sign

phenol · Apr 7, 2008

indeed. can you post detailled close-ups of both sides of this pcb wit all components visible?

JLSE · Apr 8, 2008

I dont have pics of the bottom, but there is no components on that side. Do you still need to see those? As for the ones on the front, one is labeled and is visible as SS 14, the other one reads 2100A 0627/45

phenol · Apr 8, 2008

a view of the back side will come in handy as well. im trying to trace tracks. the fact that there are no current/setting resistors is disturbing a bit as this is probably a fixed regulator then. I dont see much filtering there either. It is hard to tell what the ripple on its output is. In the case of driving a power LED ripple is of little importance as those are much more forgiving than LDs. I wouldnt take the risk driving an expensive LD with an unknown driver.

GooeyGus · Apr 8, 2008

Wont the diode only draw the amount of voltage that it needs? So as long as your current is fine wouldn't a voltage spike not be much of an issue? Or does this only hold true on the lm317-based drivers?

phenol · Apr 8, 2008

a current spike would be an issue in any LD driver. LEDs are ok absorbing short transients, tho. they dont have sensitive facets to melt. the drv above is still a mystery. it could be a current source or a simple voltage source.

JLSE · Apr 8, 2008

So what are my options with this? I usually use a 7805 regulator for the BR, im thinking of using a mini 7805 and this boost circuit together. Are there any other options to fix this problem?

phenol · Apr 8, 2008

you are ok to use a 7805 after it. in the case being there arent going to be spikes as it will regulate them. just dont omit the filter capacitors on the input and especially on the output of 7805

JLSE · Apr 8, 2008

Is there any other things i can do to eliminate the voltage spikes? The only problem I foresee with the 7805, is that the boost circuit only provides 6v steady. The 7805 will work @ 6v, but barely. I was thinking maybe there is a combination of caps or resistors I can use, instead of the 7805. Im trying to keep this as small as possible.

cheers.

Hemlock_Mike · Apr 8, 2008

Gus --

A quick note. LD's draw current not voltage. They draw current in relation to the applied voltage. That's why we graph these characteristics.

Mike

GooeyGus · Apr 9, 2008

Gotcha. I just thought that as long as your voltage exceeds the minimum requirement of the diode, that it didn't really matter, as long as the current was where it was supposed to be.

For example... what would happen to a blu-ray if you used 20v but only 38mA?

JLSE · Apr 9, 2008

I’ve always known voltage to be the pressure on a circuit (like P.S.I) and the current to be the volume (like G.P.M). Is this an appropriate analogy? I have encountered posts which would say opposite. My background in relation to electricity is as an automotive tech, head to toe. And most of my experience revolves around the 12 and 24v dc world.

JLSE · Apr 10, 2008

Okay, I put away the boost circuit today. Figured I would just focus on the PS3 sled open can idea. Well for some reason it now burns plastic. I kinda freaked as the smoke came off the tape :-X Im going to play with this some more, but its happening at 10mW! Ive been scratching my head for hours, and the best I can come up with, is maybe the shorter wavelength can focus down further? I cut a piece of normal electrical tape with a little tension on it. Took about 10sec but the little bugger made it through

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