Guys, i have a couple of single colour LED strips - 5050 - 60 LEDs per metre - 300 LEDs per strip.
Rated at 12v - they are made with a single +ve and -ve lead.
In the first instance i am trying to drive them directly from a converted PC Power Supply (rated at 40A on the 12v Rail)
Longer term i then wish to look at using a Mosfet and PWM to control them through an Arduino.
However i am having an issue where these two strings of LEDs will after 15 or 20 minutes start to cause a "crackle" in the power supply and occasionally the power supply will cutout.
I have tried two different power supplies and they both do the same thing - could there be an issue with LED strings or do i need to do something different ?
I run the same LED string for camping from a couple of 12v batteries and have no issues.
fungus:
Measure the voltage at the power supply, see if it's 12V.
Measure the current draw at the power supply.
The power supply i am using is actually from a rack mount HP server - they are rated at 100AMPs at 12v and deliver 12.43 volts unloaded and only drop to 12.23 at 60AMPs (most load i could find to put on it)
The two strings are drawing approx 10AMPs total. The voltage at that level is 12.41 volts.
jackwp:
Did you run at 60 amps for 20 minutes, Without any crackle ? I assume a crackle is an audible sound?
Yes i ran for a lot longer than that - i have a heap of these power supplies that i purchased in bulk - it starts as a clicking sound intermittently and then gets more regular, finally you can here a buzzing/crackling sound and then the thing cuts out
jackwp:
I never heard that I don't think.
It does sound like maybe over hearing, but..
Have you tested it with a fan blowing on the power supply?
The Power supplies has its own inbuilt fan that is thermally controlled (these are Power supplies for large rack mount servers that are designed for high availability etc)
I was more trying to validate my approach i.e. it is OK to drive the EBAY 5050 LED strips with a SMPS - i know the Power supply is good so i am thinking i have at least one faulty string of lights.
craigcurtin:
i am thinking i have at least one faulty string of lights.
Sounds like it, although it's hard to imagine how it could cause those symptoms. Do the power supplies get hot?
Update: Do the power supplies have a Voltage adjustment screw? Try dialing it down to 11V.
Nope the power supply is nice and cool - the fan is barely at idle (and they are screaming fans when they are needed) - there is no option to dial it down.
I will grab another LED strip and try that and see what i get