Hi everyone! I'm new here and hoping someone can guide me in the right direction. I'm trying to understand the basics of high power led lighting (1w and 3w leds). Does anyone know any good links to sites or threads that explain the basics of high power leds? I need to learn things like how to choose the right driver or drivers? Effects of different wiring (parallel vs series)? When using a driver do i still need to use a resistor if the output voltage doesn't match what the led requires? Ive spent quite sometime searching online and havent been able to find clear answers to these basic questions. Thanks
Newbie led questions
- Thread starter ledlou
- Start date
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uk_caver
Flashlight Enthusiast
To control an LED, it's normal to use a driver which regulates the current to the LED, rather than the voltage.
If the correct combination of LED
If the voltage needed to operate the LEDs was significantly* below the voltage of the power supply, you'd normally choose a driver taking that difference into account.
(*Though it's not easy to say precisely what 'significantly' means - there could be a deal of leeway depending on the precise situation).
As for recommending reference/educational sites, what's your general electrical/electronic knowledge like - (are you happy with ohm's law, etc?)
deadrx7conv
Enlightened
This is the site that explains what you need to know.
You could read every thread in each forum and go back about ~5 pages.
Check your local library to see if they can get you:
ISBN 978-0750683418
978-1848211452
978-1420076622
978-0521865388
978-0471215745
You could read every thread in each forum and go back about ~5 pages.
Check your local library to see if they can get you:
ISBN 978-0750683418
978-1848211452
978-1420076622
978-0521865388
978-0471215745
Ok, so after doing some more reading I think I may have a little bit of a better grip on things. Please let me know if this sounds correct?
Hypothetical situation- I want to power three 1 watt LEDs.
1 watt LED Specs (single LED)- Forward voltage 3.5v , Forward current 300mA
Option #1. Three 1 watt LEDs wired in series to a single driver- I would be looking for a driver that has an output of 10.5v and a current output of 900mA or less?
Option #2. Three 1 watt LEDs wired in parallel to a single driver- I would be looking for a driver that has an output of 3.5v and a current output of 900mA or less?
Option #3. One driver per LED- I would be looking for a driver that has an output of 3.5 volts and current output of 300mA or less?
How does all of this sound? If all of that sounds correct, how close does the output voltage of the driver have to match to the LEDs output voltage? Of my examples is one system more energy efficient then another? Thank you very much for the help!
Hypothetical situation- I want to power three 1 watt LEDs.
1 watt LED Specs (single LED)- Forward voltage 3.5v , Forward current 300mA
Option #1. Three 1 watt LEDs wired in series to a single driver- I would be looking for a driver that has an output of 10.5v and a current output of 900mA or less?
Option #2. Three 1 watt LEDs wired in parallel to a single driver- I would be looking for a driver that has an output of 3.5v and a current output of 900mA or less?
Option #3. One driver per LED- I would be looking for a driver that has an output of 3.5 volts and current output of 300mA or less?
How does all of this sound? If all of that sounds correct, how close does the output voltage of the driver have to match to the LEDs output voltage? Of my examples is one system more energy efficient then another? Thank you very much for the help!
uk_caver
Flashlight Enthusiast
In option 1), did you mean to write 300mA?
deadrx7conv
Enlightened
What do you plan on using to power the driver? battery or your AC power outlet? Driver selection is easy if you know what power you have, since you already have 3 1w LEDs that you want to power with it.
Scenario #1. 3 LEDs in series with a ~10.5v+ 300-350ma driver will work great
Scenario #2. ~900-1050ma at 3.5v will work great too
Scenario #3. Most expensive and possibly the least efficient as each driver draws whatever idle power it wastes x3!!! Probably the most reliable and easiest to troubleshoot when there is a failure.
The 1st two scenarios have different failure issues if the LED fails open or closed.
In series Scenario #1, if an LED fails open(open circuit like a broken wire), all 3 LEDs stop working. If it fails closed(like a jumper wire bypassing the LED), the other two continue to work at the correct current level.
In parallel Scenario #2, if an LED fails open(removed from circuit), the remaining 2 LEDs are overdriven to 450-525ma each meaning they'll likely overheat and fail soon too. If it fails closed(short circuit), none work and a cheap driver might burn out as it is a short across driver output.
Scenario #2 requires LED matching and adequate heat sinking to keep LEDs at the same temp as temp changes LEDs resistance. If 2 identical LEDs are wired in parallel, one hot and one colder, their power usage and output would be different.
Scenario #3 has a little more power wasted to multiple driver overhead. But, regardless of single point of failure, the 2 other LEDs will continue to work in spec.
There are pros/cons to every option. And, there seems to be enough reliability with LEDs and drivers to create the light that you're looking for with ANY scenario.
So, what are the LED being used for? and powered by?
Scenario #1. 3 LEDs in series with a ~10.5v+ 300-350ma driver will work great
Scenario #2. ~900-1050ma at 3.5v will work great too
Scenario #3. Most expensive and possibly the least efficient as each driver draws whatever idle power it wastes x3!!! Probably the most reliable and easiest to troubleshoot when there is a failure.
The 1st two scenarios have different failure issues if the LED fails open or closed.
In series Scenario #1, if an LED fails open(open circuit like a broken wire), all 3 LEDs stop working. If it fails closed(like a jumper wire bypassing the LED), the other two continue to work at the correct current level.
In parallel Scenario #2, if an LED fails open(removed from circuit), the remaining 2 LEDs are overdriven to 450-525ma each meaning they'll likely overheat and fail soon too. If it fails closed(short circuit), none work and a cheap driver might burn out as it is a short across driver output.
Scenario #2 requires LED matching and adequate heat sinking to keep LEDs at the same temp as temp changes LEDs resistance. If 2 identical LEDs are wired in parallel, one hot and one colder, their power usage and output would be different.
Scenario #3 has a little more power wasted to multiple driver overhead. But, regardless of single point of failure, the 2 other LEDs will continue to work in spec.
There are pros/cons to every option. And, there seems to be enough reliability with LEDs and drivers to create the light that you're looking for with ANY scenario.
So, what are the LED being used for? and powered by?
