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FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > 3 LEDS powered by USB - ended up with 3 red leds and a 9v

RSS > 3 LEDS powered by USB - ended up with 3 red leds and a 9v

oxygenthief	#1 16/02/2013 - 18h21 Top
Class : Apprenti Posts : 6 Registered on : 16/02/2013 Off line	I apologise for my lack of knowledge and having read pages of posts I am not feeling any wiser I would like to connect 3 ir leds to a usb cable in the manner used in the sticky post at the top but I cant get the wizard to provide me with the correct resistance to use when I do get a result it suggests 100 ohms which seems wrong to me. http://www.kjell.com/sortiment/el/elektronik/optokomponenter/ir-dioder-fototransistorer/ir-dioder-5-mm-10-pack-p89281 are the ir leds i want to use as I dont need to post order them, 1v 20ma can anyone suggest a resistor please thank you in advance for your help Edited by oxygenthief on 17/02/2013 at 19h06.
Stormrider	#2 16/02/2013 - 18h49 Top
Class : Légende du Forum Posts : 466 Registered on : 02/01/2013 Off line	Hi, I think the resistot calculator is right.Your type of led 20mA, mine has 100mA max and I use a 10 ohm resistor..I use ir led typ SFH 485 P . Maybe you can find a shop where they sell both, yours and mine so you can compare them. Most of the time if you use leds with round heads you must flatten them to make freetrack more acurate. If you order those SFH 485 P you need 10 ohm 1/4watt resistor.The minimum resistor you can use is 6 ohm.With 6 ohm resistor your leds wil shine very bright but won't last that long. And remember ir light is not visible for the human eye, you can check them with a digital camera device. If yo have any question just post/ask greetz Stormrider
oxygenthief	#3 16/02/2013 - 21h23 Top
Class : Apprenti Posts : 6 Registered on : 16/02/2013 Off line	Thanks for your reply, a little further investigation on the LEDS I was thinking of using show that their max rating is 130ma if they are truly the equivalent of a seimens IR Led as the site states right now I am thinking of just trying the same set up as listed in the sticky and substituting different the LEDS i can obtain... is they are max rated at 130ma then I cant see anything bad happening. I found an alternative LED schematic generator and that showed the resistor at the end of the series so now I am even more confused.
Stormrider	#4 16/02/2013 - 21h58 Top
Class : Légende du Forum Posts : 466 Registered on : 02/01/2013 Off line	Hi oxygenthief, did you also read this http://www.free-track.net/english/hardware/point_model.php I first also wasn't convinced that the calculator gave me the good resistor.With my first setup I measured the current going throug the system and so I came at 10 ohm for my setup. .Resistors aren't that expensive.So if you order 4x 25ohm resistors.You can make 100ohm resistor or 75ohm and so on for experimenting (if you have a device to measure the current) Wel, if it realy is confusing you, just trust me, order 3x IR-EMITTER SFH485P(made by osram) and 1 x 10ohm resistor.Connect them in serial(don't connect to your computer) in your set en enjoy your game. greetz Stormrider
oxygenthief	#5 16/02/2013 - 22h13 Top
Class : Apprenti Posts : 6 Registered on : 16/02/2013 Off line	hehe indeed there is no way i am connecting it to my computer, i will be using an adapter into a power outlet thanks for taking an interest I am still reading around and learning more and more, its proving quite interesting just as an intellectual exercise since i have never played with electricity before
Steph	#6 16/02/2013 - 22h52 Top
Class : Moderator Posts : 656 Registered on : 16/11/2007 Off line	hi oxygenthief, if the LEDs are identical to the LD271 (as they say in the decription), you can drive them with 1.5V and 100mA (better 80mA). Like the sfh485p. But you have to file them down as Stormrider always mentioned, otherwise you do not have enough beam angle. I used them as they are, and it's not enough. So better prepare them like this:
oxygenthief	#7 16/02/2013 - 23h16 Top
Class : Apprenti Posts : 6 Registered on : 16/02/2013 Off line	i will be doing so steph thanks
oxygenthief	#8 17/02/2013 - 19h05 Top
Class : Apprenti Posts : 6 Registered on : 16/02/2013 Off line	So I went down to the electronics shop today and bought ir diodes a pack of 200 resistors containing a variety of resistance ( no info on the pack what it contained ) a usb cable (probably the wrong kind as it turns out) I also bought a back up plan a pack of run of the mill diodes in a variety of colours red yellow etc all 5mm, a 9v battery box with on off switch, 2m of electrical wire and that was about the size of it. I also picked up a web cam a microsoft life cam HD 3000. I came home and figured out that most of the resistors in the pack had waaaaay too much resistance and went with the only resistors in the pack that were anything close to the 100 ohms the wiring diagram said I would need, 56 ohms was the closest I had so I went with it. I connected the IR diodes in series with a single 56 ohm resistor just like in the sticky, once I had everything soldered together connected to the usb cable I powered it up and checked the diodes with my mobile phone camera.... and ..... nothing undeterred I removed the usb cable from the mix and soldered on the 9v battery box and checked it again. The diodes were lighting but they were pathetically weak, I checked them on the web cam and nothing showed up apart from my lovely face. At this point I ditched the IR diodes and decided to try a single red led a 56 ohm resister attached to some wire and the battery just to see if that would show up on the camera.......worked like a charm so I ended up with 3 red leds connected in series just like the sticky (apart from the different LEDs) a 56 ohm resistor but connected to a 9v battery box and a switch it worked flawlessly. Didn't file down the LEDs either, works just great Edited by oxygenthief on 17/02/2013 at 19h06.
DeadmanWNC	#9 22/02/2013 - 13h59 Top
Class : Apprenti Posts : 17 Registered on : 08/02/2013 Off line	I nearly went with the 9v battery aswell, untill i worked out the drain on the battery and the fact I burnt my fingers on the resistors (WOW they get hot when you shove 9V through them!) Find the mAh of the battery and divide that number by the mA that the LEDS are using will give you an approximate life of the battery (then take about 70% of the time ) that wil give you a more realistic time frame for each battery. Typical 9v - 550mAh 3 LEDs using 100mA each = 300 mA (550 / 300 ) * 70% = 1.3 hrs Would be interested, to know if the theory calculations above are true - Have you replaced the 9v battery yet? Edited by DeadmanWNC on 22/02/2013 at 14h00.

FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > 3 LEDS powered by USB - ended up with 3 red leds and a 9v

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