TaskLED LFlex question

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andi15

Newly Enlightened
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Oct 9, 2008
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Hi,

i want to use the LFlex in one of my lights, but I have a question about how to connect it:

Here is written:
SWB wired to momentary action switch (electrically the same as IN-)
Click to expand...
And here:
Do NOT wire battery negative to SWB or you will compromise the current regulation path
Click to expand...
So why not connect batterie - to SWB?
That would make the construction much more easy.
Don´t understand this, could it explain someone to me?


Greetings from Germany
 
Last edited:
andi15 said:
Hi,
...
So why not connect batterie - to SWB?
That would make the construction much more easy.
Don´t understand this, could it explain someone to me?
Click to expand...

You could always have emailed me directly for an answer...

Anyhow, the current regulation requires sensing the voltage across a 0.03 ohm resistor. That sensed voltage is obviously very small. Imagine say 100mA flowing through that resistor, the voltage would be 0.1A x 0.03 ohm = 0.003V, i.e. 3mV.

So, any resistance in series with that 0.03 ohm resistor would impact the sensed voltage and therefore the regulation accuracy. That is why you NEED to wire the IN+ and IN- directly to the battery.

The switch must be wired to SWA and SWB since those are separate paths on the PCB that carry the switch signal to the microcontroller.

With high current driver designs it is critical to wire power/signals etc., as per the manufacturer's recommendation since current paths can affect the performance. Just because several PCB paths are electrically connected does not mean that the current flows equally through those paths.

cheers,
george.
 
What if I want to use the lflex in a novatac like flashlight? I see that some people have wired only the IN+, IN- and SWA or SW+.
How do that wiring works in order to access the UI?
 
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