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FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > Building Point Model for 1st time - advice needed.

RSS > Building Point Model for 1st time - advice needed.

Tomiam	#1 26/05/2008 - 13h44 Top
Class : Apprenti Posts : 5 Registered on : 26/05/2008 Off line	Hiya all, First off - thank you VERY much for releasing this free!! Ive seen the you tube videos etc and have been very impressed by Freetrack. Im planning on making a 3 LED Cap and need an experts help to ensure Im doing the right thing here. Ive read through these forums and have put together a list of what I need. I do have some questions, which Ive listed below in bold. To help, Ive also provided links to all the parts Im planning on using. Battery Pack - with two 1.2V Rechargeable AA batterys. http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=5123580 Infrad Red LEDs http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0585236A Note, I had two options for these. This one with an 80 degree viewing angle) and another with 20 degree viewing angle. I thought the 80 degree would be the better. Am I right in saying that the a) LED Led forward voltage is 1.5 V b) Led forward current is 100 mA According to the resistor wizard that means I would need (see link) three resistors, each with an individual value of 9.1 Ohms 5%? http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0150795 Any help very much welcomed and appreciated
lilpunk1302	#2 26/05/2008 - 13h54 Top
Class : Habitué Posts : 50 Registered on : 07/11/2007 Off line	That's correct But just to be on the safe side, I would recommend getting 10ohms. And there's a way to convert that to a single LED running from your power source, but I can't remember the formula, I'm sure someone else can help you on that one.
Tomiam	#3 26/05/2008 - 15h15 Top
Class : Apprenti Posts : 5 Registered on : 26/05/2008 Off line	Thank you! Bank holiday Monday here in the UK (national holiday) so all the shops are shut. I shall go and grab the bits n pieces tomorrow When you say single LED - do you mean a single resistor running from one power source? ie: Power scource to resistor to led to led to led and back? If so, that would be a lot easier to build. Edited by Tomiam on 26/05/2008 at 15h43.
tristan68	#4 26/05/2008 - 17h47 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Hello Tomiam If you're using a parallel setup , you have to use 1 resistor per led, thats 3 resistors for the entire setup. This kind of setup is an error : Since you can't guarantee each led is EXACTLY the same as the others , and since the voltage/current characteristic of a led REALLY isn't linear, you might get one led driving most of the current. This led will heat, eventually burn, and then will the 2nd, third , and so on. As a rule of thumb : leds mounted in a parallel setup NEVER share the same resistor. (the warning applies whatever the number of leds) This schematic is the correct one , just adjust the resistor values to your desired current : cya
Tomiam	#5 26/05/2008 - 17h53 Top
Class : Apprenti Posts : 5 Registered on : 26/05/2008 Off line	Superb! Thank you both for your info. Im now a LOT more confident about making the right decisions when making the 3 LED cap. Cant wait to make it now, its gonna be awesome! Sincere thanks again
tristan68	#6 26/05/2008 - 17h55 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Hello Tomiam About the SFH485P characteristics : 100 mA is the MAX value , when the led is PCB mounted. That's not the case when you're building a freetrack setup. On a freetrack setup , those leds are usually directly soldered on wires. In this setup , you shouldn't drive them with more than 75mA (OSRAM/SIEMENS specifications). So for the calcled , you should use to following values : Setup : 3led cap Power supply voltage : 2.4 v Power supply type : batteries led forward voltage : 1.5 v led forward current : from 20 to 75 ma, depending on the brightness you're seeking (usually 50mA is more than enough) cya
tristan68	#7 26/05/2008 - 17h57 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	NP Tomiam Always glad to help cya
Tomiam	#8 29/05/2008 - 19h58 Top
Class : Apprenti Posts : 5 Registered on : 26/05/2008 Off line	Well.. Spent the evening setting up my G25 and then building a Freetrack cap. Took about 30 mins to get it all set up and calibrated right but WOW! Simply... WOW! I dont know how I was playing racing games without it now! Being able to turn and see the apex coming in is amazing! Thank you again for the help! Thank you LOADS for the free software! Superb!
lilpunk1302	#9 30/05/2008 - 06h56 Top
Class : Habitué Posts : 50 Registered on : 07/11/2007 Off line	tristan68 @ 26/05/2008 - 19h47 a dit: Hello Tomiam If you're using a parallel setup , you have to use 1 resistor per led, thats 3 resistors for the entire setup. This kind of setup is an error : Since you can't guarantee each led is EXACTLY the same as the others , and since the voltage/current characteristic of a led REALLY isn't linear, you might get one led driving most of the current. This led will heat, eventually burn, and then will the 2nd, third , and so on. As a rule of thumb : leds mounted in a parallel setup NEVER share the same resistor. (the warning applies whatever the number of leds) This schematic is the correct one , just adjust the resistor values to your desired current : cya Didn't know that, will retain for future reference. The calculator tends to spit out both par and serial almost randomly (1.6v is ser, 1.7 is par) So i assumed with the proper calculations it's ok.
tristan68	#10 30/05/2008 - 07h09 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	hello lilpunk1302 The calculator tends to spit out both par and serial almost randomly (1.6v is ser, 1.7 is par) So i assumed with the proper calculations it's ok. The led wizard is done for people who don't have the knowledge to choose which setup is suited for their purpose. The wizard doesn't tell you the only way to connect leds , for given characteristics, but gives you a sure way to do it. That means the wizard integrates tresholds to choose which setup is best suited. So if your values are just under the treshold, the wizard will provide you with a specific setup, and if your values are just over the treshold, the wizard will provide another setup. I had to integrate those scenarios to be sure to always be on the safe side, which means : - take care of the component precision and characteristics dispertion. - try to choose the setup minimizing the dissipated power in the resistor(s) - try to optimize the setup to lower current in the power supply (in case of battery power). - compensate for power supply types To have a setup which suits EXACTLY your needs, the best way is to calculate the setup by hand, and to measure each component value to be sure to work with REAL values. Hope this explains why and how. cya

FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > Building Point Model for 1st time - advice needed.

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