Where are direct drive boards?

LEDBE
mknewman said:
Looking at http://www.dealextreme.com/details.dx/sku.5937 to try my hand at building a P60 but it doesn't come with a driver. I just want a simple direct drive setup, does someone sell a 3 or 5 mode driver that'll work? I don't want it to regulate, just DD off the battery.
Click to expand...
Only thing I can think of that comes close is Taskled's d2Flex. Wrong forum for this though.
 
Doesn't direct drive imply that there are no voltage or current regulators involved, which are also usually used for multi-mode brightness control? That means the only other method of brightness control would be PWM, and I think the best driver for that is the fluPIC.
 
fyrstormer said:
Doesn't direct drive imply that there are no voltage or current regulators involved, which are also usually used for multi-mode brightness control? That means the only other method of brightness control would be PWM, and I think the best driver for that is the fluPIC.
Click to expand...
I don't know about the fluPIC but the d2flex is just a PWM driver with no way to control current so I figure that "could" be considered direct drive but generally I think of it as just a direct connection to a battery with no resistor or driver of any kind. I'm not sure this guy knows what he is asking for. DD is a bad idea IMHO.
 
This board is claimed to be a direct drive PWM controller, 17mm diam, which should fit your P60 drop-in. Not sure why this board is claimed to be a P7 specific board. If it is direct drive, then the measured drive currents should depend upon the If/Vf characteristics of the LED being driven. Unfortunately, KD and DX ads are often erroneous in their descriptions, and the images often are unrevealing (as in this case, where you can't identify one of the key ICs). It looks like this board uses an ATMEL controller for the PWM, but who knows what the other big IC is.
 
saabluster said:
I don't know about the fluPIC but the d2flex is just a PWM driver with no way to control current so I figure that "could" be considered direct drive but generally I think of it as just a direct connection to a battery with no resistor or driver of any kind. I'm not sure this guy knows what he is asking for. DD is a bad idea IMHO.
Click to expand...
PhotonFanatic uses fluPIC drivers in some of his lights, so it can't be that bad of a choice. Rob Lummi uses direct drive too. As far as I can tell the fluPIC is a PWM-only driver, and as the voltage drops the brightness drops too. Not the most elegant solution, but it gets the job done -- and besides, before 2000 or so, almost all lights were direct-drive; that's just how things were back then. How quickly times change.
 
Pretty hard to do any kind of regulation on a SST-90 at 9 amps. George says D2FLEX 2.0 has been updated with a 10 amp FET now.

Oh, and thanks to everyone for helping a noob, most of this information is out there but difficult to piece together.

Marc
 
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fyrstormer, direct drive represents two possibilities actually, neither of which involvs PWM or level control.

One is a linear resistor that limits voltage/current to a safe level but disregards their variability as the battery capacity decreases. The other is an LDO regulator that keeps the voltage/current constant and passive components that keeps the ripple manageable.

Neither of which requires a complicated board, depending on the size and specifications of your chosen LED and the P60 module, you might be able to create one yourself rather than purchasing a preassembled board. just make sure whatever LDO regulator you decided to use is properly heatsinked to module.

If this P60 mdule is going to be used in a 2 cell environment what I would do is to trace and cut out a circular board from a PC perf board and install a LM317 TO-3 or 220 package in a current regulated manner along with a 0.1uF input bypass tantalum and set your Radj to whatever current you want the regulator to provide. depending on the application I'd toss a 1uF tantalum or a 25uf electrolytic cap on the output end as well. the LM317 will eat about 2V so remind yourself of that when setting the adj resistor when calculating resulting heat dissipation. The only real limitation is the output current of up to an amp, so no SST for you:crackup:
 
If you mean raw direct drive, all you need is a contact PCB and a resistor. (or if you're ballzy, skip it, a la Space Needle mods)
 
I think to some extents you can use the gauge of the wire to limit current...
I've used inductors in places of resistors...accidently, with good results. They both end up the same when they are overloaded: bursting into flames
 
Illum said:
fyrstormer, direct drive represents two possibilities actually, neither of which involvs PWM or level control.

One is a linear resistor that limits voltage/current to a safe level but disregards their variability as the battery capacity decreases. The other is an LDO regulator that keeps the voltage/current constant and passive components that keeps the ripple manageable.
Click to expand...

I will definitely not agree with you on this, I do a plot of current and if it look like this:
SunliteSlimVoltageCurrent.png


I will call it direct drive, usual it only includes a small current limiting resistor, but a power mos switching current on/off will not change this drive characteristic, i.e. I will still define it as a kind of direct drive.

On the other hand, add a constant current drive and it is not direct drive anymore. The current curve is not exponential, at the working level, any more, it is a flat line.

I has described my definition of it here.
 
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