FreeTrack Forum

Agh! I don't understand this stuff and reading the datasheets makes my eyes bleed.

I've seen reverse voltage and the bit marked forward voltage has two values!

http://www.eng.cam.ac.uk/DesignOffice/idp/components/seg_32/sfh485p/info/dsheet0.pdf

A little help greatly appreciated, fellas!

Hello tankbuster

You don't need the reverse voltage info, unless you plan to wire your leds the wrong way  

THey're indeed 2 forward voltage infos in the datasheet you provided :

1.5V and 3V  

The 1.5 V value is for "standard" operating mode.
That's the value we use in Freetrack, when working with SFH485Ps


The 3V value is only used when the led is driven by a pulse signal. In this case, the current is set only for very short durations, but can be far higher than the normal max value (10 times in our example).
BUT WE DEFINITELY DON'T USE THIS SETUP , since a pulse driver is needed.  



So : 1.5 is OK  


btw :
I suggest you shouldn't use more than 70mA for your setup (i've already written it several times , but once more isn't a pain    ).

Look at the "Forward current vs lead length" diagram, in the last page of your datasheet.


cya

Hi Tris,

Thanks for that. I have seen your writing about using 70 mA, but I'll be honest, I'm not understanding much of this so I expect I'll be back.