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tristan68	#16 16/10/2007 - 13h50 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Hello Tony. In a led setup, resistors values are led type, led current and power supply voltage dependent. I'll assume you'll go with SFH485P , right ??? There's no need to operate them at full power (specially if you power them from a battery pack, has a direct consequence on battery lifespan), 50 mA is usually more than enough. So thats : Led forward voltage : 1.5 V Led forward current : 50 mA I still need to know your battery pack or power supply voltage , to be able to specify what resistors you'll need. grretings.
tony	#17 16/10/2007 - 23h09 Top
Class : Apprenti Posts : 13 Registered on : 08/10/2007 Off line	i assume 1 AA battery will be enough? if so i believe they run at 1.5V.
tristan68	#18 17/10/2007 - 08h48 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Definitely no. If u use the same battery voltage as your led forward current, you won't know what resistor to use to limit the led forward current. Your must always : - use a power supply which voltage is a bit more than your led forward voltage. - use a current limiting resistor. BTW : Since you plan to power your leds on a battery, i'll suggest you use a serial assembly instead of a paralled assembly, or you'll drain your battery rather quickly. You'll then need a power supply which delivers at least 5v (usually a 4 x 1.5v AA battery pack or a 5 rechargeable AA style battery pack, for 6V).
tony	#19 17/10/2007 - 11h55 Top
Class : Apprenti Posts : 13 Registered on : 08/10/2007 Off line	so i need to create a serial assembly with 4 batteries? how do i do that. and if i do that then can u now tell me what resistors i need? hey tristan are u on msn? maybe this would be easier if i could talk to u live on msn
Kestrel	#20 17/10/2007 - 12h42 Top
Class : Webmaster (admin) Posts : 780 Registered on : 13/07/2007 Off line	Are you using SFH485P leds? Support FreeTrack
tony	#21 17/10/2007 - 13h44 Top
Class : Apprenti Posts : 13 Registered on : 08/10/2007 Off line	im gonna find out today if the local electrical shop supplies them. the problem is most of the answers im gettin here involve ifs and buts so i dont seem to be gettin anywhere fast. i realise most people on these forums probably have a lot of experience and its maybe frustatin explainin things to a newbie like me if the local shop supplies those led's and i use a 4 battery assembley then what resistors do i need? if they dont have that model and i have to get another kind then i assume the guy will no what resistors to get right? i also believe i have to a solder iron, and have a coat hanger handy? also info on how to make this battery assembley. basically an idiots guide from start to finish on how to get freetrack assembled and good to go would be fantastic. im on msn most days at work (now) and sometimes at home is anyone would talk with me about this tonylaffery@hotmail.co.uk
Kestrel	#22 17/10/2007 - 16h36 Top
Class : Webmaster (admin) Posts : 780 Registered on : 13/07/2007 Off line	tony @ 17/10/2007 - 13h44 a dit: if the local shop supplies those led's and i use a 4 battery assembley then what resistors do i need? For 3 SFH485P LEDs connected in series with 4 1.5v AA batteries, a single 30 Ohm resistor is required. Colour code: Orange Black Black. if they dont have that model and i have to get another kind then i assume the guy will no what resistors to get right? Sometimes, depending on the store, how busy they are and how knowledgable the storeperson is. The most important part is to get the identity of the led so you can find its specifications, which should be in their online/hardcopy catalogue. i also believe i have to a solder iron, and have a coat hanger handy? Yep. And some solder to 'glue' the component wires together in series, like a daisy-chain. A coat hanger would be good, don't be afraid to use your imagination! For inspiration: http://freetrack.online.fr/forum/index.php?showtopic=2 also info on how to make this battery assembley. You can buy them, described as a '4 AA cell/battery holder'. Support FreeTrack
tony	#23 18/10/2007 - 11h09 Top
Class : Apprenti Posts : 13 Registered on : 08/10/2007 Off line	bah, i checked the local electrical shop and they dont sell led's so im gonna have to wait till saturday and travel a bit further afield. i would buy it online but im still not to sure where to buy what i need.
HugoC	#24 18/10/2007 - 16h23 Top
Class : Apprenti Posts : 4 Registered on : 07/10/2007 Off line	"i would buy it online but im still not to sure where to buy what i need." You could try Avnet electronics if U are in the USA. http://www.em.avnet.com/ Search for SFH485P, they are about $0.35 a pop. I think they accept small orders with $8. minimal for shipping. Check with them first in any case. Local outlets would only accept bulk order of ~500. At least it's the case here in Montreal. Hope it helps, HugoC Edited by HugoC on 18/10/2007 at 16h24.
Mdds	#25 18/10/2007 - 16h56 Top
Class : Apprenti Posts : 26 Registered on : 02/10/2007 Off line	Hi tony One option since you live in the UK is to order to components from http://www.led1.de/shop/ They don't have SFH485P LEDs but you can order these http://www.led1.de/shop/product_info.php?pName=led-5mm-infrared-8mw-10-pcs-p-413 And if you decide to power your setup with 9V battery, you also should order these resistors http://www.led1.de/shop/product_info.php?pName=resistor-220-ohm-1-w-5-p-499&cName=resistors-c-6 The only minor problem with those LEDs is the narrow beam angle but just sand paper top of them flat and everything is ok Edited by Mdds on 18/10/2007 at 16h57.
tony	#26 19/10/2007 - 17h50 Top
Class : Apprenti Posts : 13 Registered on : 08/10/2007 Off line	think the site im gonna go with is this one - uk.farnell.com so i need to get 3 IR 5mm led's, ideally SFH485P 1 resistor to go with those led's and a 4 AA battery holder solder iron and solder if someone could point me to those items on that site, or any other site that would be fantastic.

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