Re: FS: >110mW Blu-Rays - available
sk8er4514 said:
the driver uses some current to do its work. jayrob must have measured from the batteries as well when labeling that, the diode is probably getting a little less.
The difference between the current in and current out with linear drivers is only a couple of mA. Not 55mA..
In fact, with linear drivers it doesn't really matter at which point you measure the current. It's pretty much the same all the way, as there is only one way through the driver.
So there, you can just as safelly (or more, cos you don't have to disconnect the load) set the current through the load, by measuring the current from the battery.
Boost drivers convert the relationship of power going in, and the power coming out, and at a high efficiency - the power out is not that much lower, than the power going in.
With a linear driver, you have to give it the current the load needs, but at a higher voltage.
For example, a red at 333mA with a 317:
The diode will be getting 333mA at around 3V = 1W of power coming out of the driver. (0.333A x 3V = 1W)
The driver will need more than 6V to operate. Two Li-Ions are in the optimal range, so it will get 8.4V when batteries full. 0.333A x 8.4V = 2.7972W going INTO the driver with the batteries full!
This means, the efficiency of a 317 with full Li-Ions is only 35.7%! 64.3% gets converted to heat by the driver, because it has to give the load the same current it is drawing, but at a much lower voltage. As the batteries slowly discharge to 6V, the efficiency slowly climbs to 50%. 50% is still getting converted to heat in the driver.
The average efficiency is ~43%, which means, that only 43% of all the battery capacity ever gets used. The rest is lost as heat.
A good boost driver on the other hand, hardly ever warms up. That's because it doesn't discard excess power, but converts the power into what the load needs. There are some losses in certain components on the driver, and they slightly warm up, but the components never go above 40°C, or feel hot (measured with an IR non contact thermometer).
The efficiency is a pretty constant 84-86%, so the batteries get used to their fullest. Only 14-16% is lost as heat.
Otherwise, i am very flattered, that you people believe, i can make a perpetuum mobile. I wish i could. But i can't..
GamerBR:
GamerBR said:
Or it takes more than 125mA from the battery but the driver only delivers 125mA to the diode?
Yes.
It has to, as the 3.6V battery doesn't have enough voltage for a blu ray diode which needs almost 6V.. The current through the diode is ALWAYS 125mA, be it on a full or completelly empty battery.
Oh, and one important thing. PLEASE don't use the diffraction grating for a few days! Don't take the original lens out! Many people get garbage on the diode window, when they do so, and then make it worse by "cleaning" attempts.
Please make sure you read the cleaning instructions, and otherwise, make sure they are never needed.
Also, PLEASE do NOT atttempt to open the module that is in the head without special instructions! There is an IMPORTANT step to do FIRST!
I can show you pictures of what it looks like, if you're interested. It's much safer than taking it appart.