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FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > Which IR Led´s the best?

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druckgott	#1 20/07/2008 - 12h17 Top
Class : Apprenti Posts : 2 Registered on : 20/07/2008 Off line	Hallo, which ir led´s the best? What Half angle should the Led have? What Radiant intensity should the Led have? thx druckgott
marcusw	#2 20/07/2008 - 17h55 Top
Class : Habitué Posts : 150 Registered on : 18/04/2008 Off line Www	Hello druckgott! The wider the the half angle, the better. Radiant intensity isn't really an important factor here, since you are trying to detect the led itself, and not illuminate anything else. Most leds are going to half a half angle that is too narrow anyway, so the best bet is to sand down the tops yourself until is a mm or two above the cathode, a little more than that is fine too. Then use a finger nail buffer to smooth it up. The only really wide angle leds around that suit this project are osram's sfh485p's, and they are hard to find. They also operate at a higher voltage than some cheaper ones out there, so sanding others down is a better option. Marcus The only way to fly!!!
druckgott	#3 20/07/2008 - 18h53 Top
Class : Apprenti Posts : 2 Registered on : 20/07/2008 Off line	This one is the best? http://www.conrad.de/Bauelemente-Bausatze/ir_emitter_sfh485p.sap This shop is in my area. So I can by it and they are very cheap. And I don´t have to grind it. How much Voltage have I to use if I put 4 Led´s in row? Or is it better to put it parallel. I don´t find the info of the Voltage on the page? thx druckgott
mrwell	#4 20/07/2008 - 21h30 Top
Class : Apprenti Posts : 3 Registered on : 20/07/2008 Off line	Hello, this is my first post in this forum. I've read a lot and I saw you awesome models. Now I wanna be one of you and I have 3 ir leds named OP295A. I wanna know if I can use them for my model. I've tried to introduce the data in the circuit calculator but no luck. I want to use 4 AA batteries (I have also the mounting for them). Here is the data sheet of the leds: * LED, T-1, 3/4 * Wavelength, typ:890nm * Power dissipation:333mW * Current, forward If:1.5A * Voltage, Vf max:4.0V * Angle, viewing:50° * Case style:T 1 3/4 * Temperature, operating range:-40°C to +100°C * Current, If av:1500mA * Current, If max:5000mA * Current, peak pulse:5.0A * Current, reverse leakage max:10µA * Diameter, head:4.95mm * Length / Height, external:7.62mm * Length, lead:19.05mm * Pitch, lead:2.54mm * Power, radiometric min:44mW * Temp, op. max:100°C * Temp, op. min:-40°C * Temperature, storage max:100°C * Temperature, storage min:-40°C * Time, fall:250ns * Time, rise:500ns * Voltage, PIV max:2.0V * Wavelength, peak:880nm Thanks in advance!
tristan68	#5 21/07/2008 - 12h06 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Hello mrwell these leds will work with freetrack. Wavelength, peak:880nm Very good , better than 920 or 940nm Angle, viewing:50° A bit narrow , but you can still widen the angle by filing the led case I've tried to introduce the data in the circuit calculator but no luck. May I ask what values you tried to use ??? Thx in advance. cya
mrwell	#6 21/07/2008 - 21h53 Top
Class : Apprenti Posts : 3 Registered on : 20/07/2008 Off line	Thanks for the answer! I introduced 6 Volts with batteries (4 X 1,5V), 4 Volt of the LED specs and the current is the problem. In the specs I see 1500-5000mA and it doesn't give me any result with those. So I introduce 500mA or about (the max allowed in the calculator) but I don't know if the LEDs could suffer if I use the resistor it gave me. The result I achieve with the common calculation is: R=(V-Vf)/(N leds* If)=(6V-4V)/3*1500mA=0,8 Ohm Then, what resistor should I use? 1 Ohm? none? Thanks again!
tristan68	#7 22/07/2008 - 01h25 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Hello MrWell The problem is the OP295A is normally tailor-made to be pulse driven. That's not the case in freetrack use, we use constant current drive. So most of the values you got are false , since there are values used for pulse drive. By looking at the datasheet, if found this led operates at max : 150mA constant current. I suggest you don't drive it with more than 100mA. At this current , the led will show a forward voltage of about 1.4v so your values are : Setup type : 3dot cap or clip Power supply model : batteries Power supply voltage : 6v Led forward voltage : 1.4v Led forward current : 100mA that gives you : Serial Assembly 3 leds 1 resistor : 18 ohms 5% 0.5w or 1w cya
tristan68	#8 22/07/2008 - 01h30 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Then, what resistor should I use? 1 Ohm? none? Leds are diodes, not light bulbs : they are current driven , not voltage driven. Rule of thumb : NEVER use a led without a resistor, or a current limiting device
VoodooWoo	#9 22/07/2008 - 07h52 Top
Class : Apprenti Posts : 3 Registered on : 22/07/2008 Off line Www	Hi @ all! At the following link you can find an very good calculator for our purposes. It is a german website, but you can switch to english language. I hope it can help you a little bit http://www.led-tech.de/en/Light-Emitting-Diodes/5mm-LEDs/IR-LED-LT-591_1_4.html Greets Voodoo (from germany) Edited by VoodooWoo on 22/07/2008 at 07h53. http://sig.sysprofile.de/iconsig/sysp-70548.png
mrwell	#10 22/07/2008 - 14h25 Top
Class : Apprenti Posts : 3 Registered on : 20/07/2008 Off line	Thanks very much to both. Very useful info. Now I see my mistake I will post my model when done!. Cya!

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