# LED Driver questions



## sigmo (Oct 22, 2010)

Hi folks. First post here.

I recently bought a couple of LED driver modules as well as a couple of 3 Watt LED modules from an EBAY supplier called "lightobject.com".

I got the goodies quickly and am anxious to play with them.

The LEDs are straightforward enough, but no documentation came with this order, and I've searched their site for data and come up empty.

So I'm looking for any advice or tech data that anyone might have for the little 3-Watt (750mA) driver modules that I got. I don't even know the true pinout for them, so that makes things a bit spooky 

I suppose I could try to trace the circuits out and see if I can look up the active parts by the numbers on them, but I figured someone here may have used these modules and will know the lowdown.

Here are some photos of the modules and one of the LED module just for good measure.

















Now. It looks to me like the non-component side of the driver module ought to be the *input* side with the center "dot" being the positive power input and the ring around the edge being the negative input feed. I figure this would let someone just mount the module in the end of a typical flashlight barrel and the "tip" of a AA battery would make contact with the center "dot" and the outer ring would contact the barrel of the light.

Then, that would leave the two terminals on the other (component) side of the board as the *output* to feed the LED. On that side, I'd imagine that the outer ring would, again, be the negative side of things (common to the ring on the back, and connected by a couple of feed-throughs - aka plated-through-holes). So the other "terminal" would naturally be the positive feed to the LED.

But, on the website for this company, there is a post to a forum that shows the guy feeding power into the component side of the board, and driving the LED from the back side. Then there's a post below that one with a guy stating that he tried it that way, and it doesn't work.

So I'm thinking that the post showing the power applied to the component side of the board is wrong.

What do you folks say?

I know this is a dumb post, but I'm new to all of this, so there ya go!

Sigmo


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## Noctilucent (Oct 23, 2010)

Usually when you source from these cheap e-bay sellers, go for the cheapest one, and can't find any technical information... just look for another seller with essentially the same product.. they might list the information.

I just happened to see a module similar to yours (perhaps the exact same) a while back while looking for some side-emitting optics, so I dug that up out of the browser history... won't link to it, but here's the info from that seller's page:



> Specification for the Driver:
> Quantity: 1pc
> Operating voltage: 3V-9V
> Current (peak): 350-700mA
> ...


From the picture supplied, the output + would be at the yellow package, and the output - would be the other open contact (not the outer ring.. though they may be connected.. grab a multimeter and find out) above the coil.


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## sigmo (Oct 23, 2010)

Thanks for that information. It sounds similar if not exact for this device.

The connections sound correct based on what I figured out by tracing the circuitry last night. I posted this information to the supplier's website forum as well.

I looked up the "C310" marked on the IC on the little board and found a likely suspect by searching the web. It's likely that this is a Zetex ZXSC310.

Based on the datasheet for that IC, and tracing the little board, I came up with this as a schematic for the driver board:






Based on that schematic, the only way I could imagine the board working was to connect the LED module between terminals A (positive) and B (negative). Then, the positive side of the power source is fed into terminal D (which is electrically tied to terminal A on the board). The negative side of the power supply is tied to the "ground ring" which I've called terminal C.

This results in a hookup as shown here:





















Connecting things this way, the unit seems to begin lighting the LED with about 2.3 Volts applied. The brightness of the LED seems to max out when the input Voltage reaches about 3.3 Volts. From that point upwards, the brightness appears to be reasonably well regulated. I stopped at about 8 Volts because the datasheet for the ZXXC310 states that the maximum voltage for the IC is 8 Volts.

I'm not sure where the advertised voltage of 12 comes from, but I wouldn't exceed 8 Volts on the input, and it's probably best to stay a bit below that for a safety margin.

I also think the wiring setup I've arrived at here makes sense because when used in a typical flashlight, the module would be mounted so that the positive "tip" of an AA battery could contact the center circular "pad" on the non-component side of the board and the barrel of the flashlight would contact the "ground ring" that surrounds the board on both sides. That would allow easy mounting in a flashlight while allowing contact to be made easily.

Then, on the other side of the board (the component side), the connections could be taken off of the small solder pads for wires actually feeding the LED module. At least that's what makes sense to me.

Again, it's unfortunate that there is no documentation supplied with these modules and that there is no documentation for them on the supplier's site. I would not have purchased these units had I known that no data was available. I made the foolish assumption that data would come with the units OR it would be available on the supplier's website. 

Anyhow, that's what I've figured out on my own, but I'd still prefer to have the actual data from the designers.

The LED modules are straightforward and operate the way I'd expect when driven directly from an adjustable power supply. Setting the current limit to 750mA gives a very bright output as expected.

When connected through the little driver module wired as I've shown, the drive seems reasonable, with the circuit limiting the drive current over a fairly wide range of input voltage. For a flashlight, this setup would run best with, say, three or four 1.5 or 1.2 Volt cells in series, or, perhaps, two Lithium cells in series.

What do you folks think. Does this all seem reasonable? Thanks again!


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