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RSS >  LED Assembly Wizard??, Is it bugged?
Niek #1 25/03/2008 - 01h17

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Hi!

I'm ordering some parts to build me a 3-point clip with SFH485P's.
They need 1,5V and 100mA.
I will power them with USB (with a PTC-fuse, 0,2A trip), so output is 5V.
The leds are in series so when I want to calculate the resistor I get:
5V - 3x 1,5V = 0,5V over resistor.
R=U/I => 0,5V/0,1A = 5 Ohm resistor

When I calculate the same with the LED assembly wizard on this website it says I need a 20 Ohm resistor!

What's going on?
Edited by Niek on 25/03/2008 at 01h31.
larockonoli #2 25/03/2008 - 05h26

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let me know if you get your setup running...  I am thinking about running off a USB as well, but I have no clue on the fuse size, etc.  so I would rather  make sure someone has success on it first.
tristan68 #3 25/03/2008 - 11h16

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Hello Niek

I just checked the wizard.

For your settings :

- 5v USB power
- 3 x SFH485P
- 1.5v led voltage drop
- 100 mA

the wizard suggests the following, which IMO is OK  :easy:  :

Posted Image

Can you please confirm the values you entered ??



BTW :

- The wizard doesn't take account of the PTC voltage drop. You have to see for that. Next version will implement it.

- You shouldn't power your SFH485P's at 100mA, it's the max value when led is PCB mounted. For cable mount, the max suggested value is about 75mA.


Cya
George #4 25/03/2008 - 12h27

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Hi Niek,

you typed 1,5 instead 1.5

I made the same before... :rolleyes:
Niek #5 25/03/2008 - 18h38

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George @ 25/03/2008 - 12h27 a dit:

Hi Niek,

you typed 1,5 instead 1.5

I made the same before... :rolleyes:


Haha, that's it!  :pinch:  :D

And thanks for the tip about the 75 mA and PTC voltage drop!
I'll check it out!

I already ordered some female mini usb connectors to connect the usb cable to my future device.
Edited by Niek on 25/03/2008 at 18h41.
tristan68 #6 26/03/2008 - 19h54

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Hello niek.

NP , and good luck for your setup  :)

cya
Syquus #7 19/01/2009 - 16h42

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Does the LED Assembly Wizard online work? I'm trying to use it, filling with my info, but it doesn't give any responses. Tried with FF and IE

Regards
Syquus #8 19/01/2009 - 17h13

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I'm sorry for my last posts. It's working perfectly. I was introducing wrong values. (out of range for programmed webpage)
kookookalvy #9 23/01/2009 - 18h53

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tristan68 @ 25/03/2008 - 11h16 a dit:

Hello Niek

I just checked the wizard.

For your settings :

- 5v USB power
- 3 x SFH485P
- 1.5v led voltage drop
- 100 mA

the wizard suggests the following, which IMO is OK  :easy:  :

Posted Image

Can you please confirm the values you entered ??



BTW :

- The wizard doesn't take account of the PTC voltage drop. You have to see for that. Next version will implement it.

- You shouldn't power your SFH485P's at 100mA, it's the max value when led is PCB mounted. For cable mount, the max suggested value is about 75mA.


Cya



Hey, I've never responded on a forum before. I used a 33ohm resistor for mine (and my buddies) You are trying to cut down output amps from 100mA to about 20mA I think, Mine ends up at 45mA with calculator thing. No problems with the USB, (so far) I guess if it were gonna fry my Motherboard it would have already. (I hope) I tried to donate too, but what a pain.
tristan68 #10 23/01/2009 - 23h06

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Hello kookookalvy

can you tell me what params you used ?

thanks.

cya

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