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PostPosted: 01.02.2005 07:10 
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Junior Modder
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Joined: 01.02.2005 06:59
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Location: Plano, Texas
Looking at this schematic, can you think of any reason that I could not connect 5 - 10 LEDs to this, as long as each of the individual LED lines had it's current limiting resistor inline before the anode? I need it to be passing the 5v straight out to the attached LED's. Would I connect all of the +'s sides to the same point, as well as all of the -'s?

I'm looking to use this to accentuate some flames in a mod that I am wrapping up on. Would like the flickering of the flames to be something functional (HD Activity), but I need it to power

Thank you for your guidance.

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PostPosted: 01.02.2005 10:30 
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You can connect multiple leds to this circuit. Only thing to remember is not to exceed the current limit of the optoisolator. 100mA should be safe to use. Every time that you connect something in parallel, they will use additional current. Try to connect as many components in series to keep safe.

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PostPosted: 01.02.2005 19:34 
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So... when looking at spec sheets for Optoisolators, what line is it that I should be concerned with, with regards to the current limit?

Just want to make sure I'm reading the right info.

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PostPosted: 01.02.2005 21:23 
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Datasheets usually give only volts to the output side of the optoisolator. As the isolator output is formed like a NPN-transistor and it is not a power component, I would suggest that 100mA as a limit. If you need higher currents, control for example a power transistor with the output of the optoisolator.

I tried the circuit with 12 volts and it worked perfectly. This way one can connect several leds in series and take only low amount of current.

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PostPosted: 01.02.2005 22:14 
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Junior Modder
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Joined: 01.02.2005 06:59
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Ok, let me make sure I get this straight...
Let's say I set this up for 12v power, and I have 9 LED's that I want to light up. Let us also say, for the sake of discussion, that the highest forward current required by any of the LED's is 30mA.

If I have three 4v LED's in series, the chain will only draw 30mA?

So If I were to have 2 more chains (for a total of 3 "series" chains with 3 LED's per strand) and the LED's used there are rated @ 30mA as well,
would I only be using 90mA of current to drive these strands of lights due to the fact that they are serial?

Or is a serial arranged strand going to add up the current requirements of each LED, thereby making a strand of 3 = 90mA?

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PostPosted: 02.02.2005 00:01 
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The same current is going to pass all the leds in the same series string so they will only use 30mA. Connect these series strings in parallel and you have to multiply the current value with the amount of the strings. So it makes sense to connect as many leds in series as possible.

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