FreeTrack Forum

Hi I need some help with getting my resistors. I have made my hat and used cheap ir's from china for my 1st project only to find out they were flashing ir, if they were not it would have been a success.   LOL

I even got the right resistor for this!!

The hat system is based on a 9 volt 300mA power supply, using the component wizard it asks for a 75ohm resistor for the LEDs below.

LED Assembly Wizard

LED ASSEMBLY       S : serial assembly
RESISTOR COUNT     1 resistor(s) needed for the complete kit
RESISTOR THEORICAL VALUE     72 Ohms
RESISTOR CHOICE E24 SERIES     Resistor value     75 Ohms 5%
Current     96 mA
Dissipated power     0.69 Watts
Total current in assembly     96 mA

LEDS

OSRAM - SFH485P - IR EMITTER, 5MM, 880NM

* IR EMITTER, 5MM, 880NM
   * Wavelength, Typ:880nm
   * Forward Current:100mA
   * Voltage, Vf Max:3V
   * Viewing Angle:160°
   * Case Style:Radial
   * Operating Temperature Range:-40°C to +100°C
   * Current, If AV:100mA
   * Full Angle:160°
   * Half Angle:80°
   * LED / Lamp Size:5mm / T1.3/4
   * Max Radiant Intensity:6.3mW/Sr
   * Min Radiant Intensity:3.15mW/Sr
   * Pitch:2.54mm
   * Radiant Intensity:48mW/Sr
   * Turn Off Time, t Off:0.5µs
   * Turn On Time, t On:0.6µs
   * Voltage, Vf Typ:3V
   * Wavelength, Peak:880nm
   * LED Colour:Infrared

HELP

Can anyone guide me to the right resistor/part number on this website http://uk.farnell.com/ as I ordered the wrong ones last time,
I am not a electrical wizard like some of you.

Many thanks in anticipation.

This is a marvelous peice of free software and I can't wait to get going.

You can try these:

http://uk.farnell.com/jsp/level5/module.jsp?moduleId=en/207220.xml

select 75R

I recommend order also higher values, with 75 ohm your leds are very bright and may give some ghosting-light flares. order also 100R ---> gives 70 mA.

Thank you for your advice and time, at least we have somewhere in the uk to get these parts. When I finish it I will post some pictures.

Will the 100R dim the LED?
Would rounding the tops off slightly help?

They are the closest LEDs to the 80 degree ir's on the site and carry the SFH485P part name, I hope they will do the job.

Maybe it's better to order these: (I advised you to order 0.25 Watt)

http://uk.farnell.com/welwyn/mfr5-100r-1/resistor-0-75w-1-100r/dp/9497340

because you're using a serial build... more power ....  0.75 Watt!


70 mA is enough to power the SFH485P.

If they are real  SFH485P 's they should be flat / otherwise rounding the tops off slightly will help!

Are you going to use IR modded webcam? IF you are, i recommend using 25mA. With 70mA and ir modded cam the leds are too bright. i think 50 mA is enough for any cam ir modded or not. + less milliamps, longer lifespan of leds. / (batteries if you use them.)
Note: this recommendation only for SFH 485 type.

And if you use flat Osram SFH 485P leds, you dont want to sand or round them in any manner, they work flawlessly without any modding.

Have a nice tracking....  

Snow

Hey!!!

Thanks a lot everyone, I have a Logitech express that I have modded as in the guide on the site. Seems to stay at 25fps but that should be okay, I still need to build the floppy disc part but that's not a problem. Is there any tips on upping this cams frame rate to 30fps or is that about it.

I have ordered 75r and 100r so should be good to start putting it together again tomorrow.

I used the 100R's and its perfect, works like a dream. LEDS no problems no sanding required.

Many thanks.