I've been messing around with an angel eye style LED ring - a ring of around 60-odd bright LEDs on an aluminium substrate.
I don't have a datasheet for it, but on the listing it stated:
When I hook it up to my small bench-top power supply set at 12VDC (constant voltage) it draws around 1A and before too long gets pretty hot. It's a lot brighter than I need it to be when I run it like this.
After a bit of trial and error I found that a 3Ω resistor would result in the LED ring drawing 0.35A from the PS (still set at a constant 12VDC) and the voltage measured across the LED ring would drop to around 11V - it was still bright enough for my needs and ran cool enough to the touch.
The resistor I used in my little test has quite a low power rating, I'm sure (perhaps 1/4W) - it does get hot, but you can still touch it without any discomfort.
I'd like to include a 3Ω resistor in with this simple circuit, but I'm at a loss as to how to calculate the power rating I need. I've looked up how tos, and I'm aware of this excellent calculator but the fact that this is an LED ring made up of 60 or so warm white LEDs and not having any info with regard to it's Vf throws everything off - ie. in the example above a 24Ω resistor should drop the 1A down to 0.35A when used with a white LED with a Vf of 3.6 - but with this LED ring it turned out it had to be a 3Ω resistor.
I'm an electronics dunce - this stuff blows my mind - any pointers on how I should proceed? Maybe the answer has been staring me in the face with the stated power of the LED ring being 11W? I dunno, I just can't get the numbers working.
Many thanks!
I don't have a datasheet for it, but on the listing it stated:
- Power: 11W
- Input voltage:12V DC
- Allowable maximum current: 1100mA
When I hook it up to my small bench-top power supply set at 12VDC (constant voltage) it draws around 1A and before too long gets pretty hot. It's a lot brighter than I need it to be when I run it like this.
After a bit of trial and error I found that a 3Ω resistor would result in the LED ring drawing 0.35A from the PS (still set at a constant 12VDC) and the voltage measured across the LED ring would drop to around 11V - it was still bright enough for my needs and ran cool enough to the touch.
The resistor I used in my little test has quite a low power rating, I'm sure (perhaps 1/4W) - it does get hot, but you can still touch it without any discomfort.
I'd like to include a 3Ω resistor in with this simple circuit, but I'm at a loss as to how to calculate the power rating I need. I've looked up how tos, and I'm aware of this excellent calculator but the fact that this is an LED ring made up of 60 or so warm white LEDs and not having any info with regard to it's Vf throws everything off - ie. in the example above a 24Ω resistor should drop the 1A down to 0.35A when used with a white LED with a Vf of 3.6 - but with this LED ring it turned out it had to be a 3Ω resistor.
I'm an electronics dunce - this stuff blows my mind - any pointers on how I should proceed? Maybe the answer has been staring me in the face with the stated power of the LED ring being 11W? I dunno, I just can't get the numbers working.
Many thanks!