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Ramzinator	#1 14/05/2008 - 01h49 Top
Class : Apprenti Posts : 3 Registered on : 14/05/2008 Off line	Ok so i was all ready and everything after spending like 50$ on supplies.I have this power adapter that is 500ma and i can chose from a voltage series of 1.5 - 3 - 4.5 - 6 - 7.5 - 9 - 12. i got 3 Infrared LEDS from radio shack which cost 3$ each like wth.. i'am only 14 so i dont have a credit card to buy them for 50 cents online. The LEDS i have are 150ma forward current and 1.3 top 1.7 volts of forward voltage. The resister i have is a 9 ohm resister. This is how i set up my FT hat = LEGEND p= positive n= negative r= resister P side of power supply R P side of LED 1 N side of LED 1 P side of LED 2 N side of LED 2 P side of LED 3 N side of LED 3 N side of power supply ( I did it perfectly i even tested this out with a small light bulb and it worked but the LEDS wont shine no matter what i do to them! please help. THANKS!
tristan68	#2 14/05/2008 - 09h06 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Hello ramzinator according to the given infos , everything seems fine. 1) Are you sure the leds aren't on ?? I say this because if the leds are 940nm models, you won't see if they're on. They won't light up , even a little bit (to human eyes). 2) Are you sure one of the leds isn't inverted ? 3) 9 ohms seems really a low res value to me. Can you tell me what voltage setup you used ? thanks cya
Ramzinator	#3 14/05/2008 - 15h35 Top
Class : Apprenti Posts : 3 Registered on : 14/05/2008 Off line	tristan68 @ 14/05/2008 - 09h06 a dit: Hello ramzinator according to the given infos , everything seems fine. 1) Are you sure the leds aren't on ?? I say this because if the leds are 940nm models, you won't see if they're on. They won't light up , even a little bit (to human eyes). 2) Are you sure one of the leds isn't inverted ? 3) 9 ohms seems really a low res value to me. Can you tell me what voltage setup you used ? thanks cya 1) I'am sure the LEDS aren't working because they wont shine and i have the ones that the handbook suggested me to get something like OSRAM but anyways they would shine if there working 2)i should try to make it agian and make sure it's not inverted because i think that was the problem. 3) i used 4.5v but my power supply gives 30% more so that would be around 5.9v. I even checked the calculator and it said that i should use a 9.1 ohm resister.
Don 'Chito' Lito	#4 14/05/2008 - 16h21 Top
Class : Apprenti Posts : 8 Registered on : 01/05/2008 Off line	Try hooking the LED's in the opposite direction you have now. It doesn't hurt the LED to hook it up backwards. They just act like a diode and when the current is reversed, they block current flow. Otherwise your series circuit appears to be hooked up correctly.
fatboy	#5 15/05/2008 - 07h20 Top
Class : Apprenti Posts : 12 Registered on : 14/05/2008 Off line	The negetive of the LED's is usually the shorter lead off the LED itself (given you havn't snipped them shorter). Might just be your power supply, reverse that before you go and take your solders apart. Start with the easiest fix and work from there. Also, just saying, the LED's I bought sound much the same as yours, from circuit city. Mine came in a pair, one is a collector, which is clear and one is an emmiter, which is tinted. You want the tinted emitter. You won't be able to see any light, or glow emitting from them at all with your eyes, you will have to put them in front of your webcam as it will pick up the light emmited. Edited by fatboy on 15/05/2008 at 07h25.
Ramzinator	#6 15/05/2008 - 07h49 Top
Class : Apprenti Posts : 3 Registered on : 14/05/2008 Off line	ok il try to see if the webcam picks up anything so il make another FT really quickly tommorow and il tell you guys what happens.
tristan68	#7 16/05/2008 - 15h56 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Don 'Chito' Lito @ 14/05/2008 - 16h21 a dit: Try hooking the LED's in the opposite direction you have now. It doesn't hurt the LED to hook it up backwards. Sorry but false. each diode a a max reverse voltage value. for rectifier diodes, this value is usually high (400 - 1000v) so its ok to hook them backward without harming them. For LEDS this max reverse voltage is often low, and is model dependant (ie : 5v for the SFH485P. So, if you're testing diodes, be sure to operate at a voltage lower than the reverse voltage of your diode, since a reverse voltage higher than the max reverse voltage can damage your led. @ramzinator : CC sfh485 emit a small amount of visible light when operating. A very weak red shine can be seen, mainly when in a darkened room. In full light, you usually can't see anything with bare eyes. cya
fatboy	#8 17/05/2008 - 06h03 Top
Class : Apprenti Posts : 12 Registered on : 14/05/2008 Off line	Ah, apologies. I'm only using a 4.5 V PSU, I didn't even think of others using a different one lol. Doh.
marcusw	#9 17/05/2008 - 14h36 Top
Class : Habitué Posts : 150 Registered on : 18/04/2008 Off line Www	My solution: I believe you made a typo in the led wizard and put 1.5 volts instead. As a matter of fact, I'm sure you did. And you put 1.7 as the forward led voltage. the result would have said 9 ohm (3 of them) in a PARALLEL circuit. THIS IS ALL WRONG. You should have put 4.5 volt power, with 1.3 led. So you need to go to Radio Shack and get a 20 ohm resisor. This is correct for your setup. I use the same leds, so I know this will work. And no, you won't see any glow with these leds with the naked eye. Side note: Never go with the highest number for you leds, 1.3 volts is all you should go with, remeber that hair take a long time to grow back, Edited by marcusw on 17/05/2008 at 14h46. The only way to fly!!!

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