Checking voltage on LED power supply ?
Not RV related per se, but figured someone here would know. I recently purchased a set of LED lights to put some path lights to avoid tripping. Hooked up the lights and everything works fine. Ne...
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jkwilson wrote:Gdetrailer wrote:JoeH wrote:Tom_M wrote:
Switch your meter to AC and check. Most likely one supply is AC and the other is DC.
Nope-- meter stays on "0" regardless of being on AC or DC.... but the LED lights out in the yard work. Strange
Post a pix of the power supply with the model number..
I suspect it is a high frequency switching supply and has no or little filtering on the output.. Most meters will not read at all or properly 15Khz-30khz frequencies which most switching supplies operate at which could explain why you can't get a reading but the lights work.
Even with poor filtration, the output of a switch-mode supply is still DC and could be measured with any DC volt meter.
No, not always the case, switched mode power supplies by their very design CAN present a high frequency AC output.
Switching supplies convert 120V AC 60hz to 120V DC via a bridge rectifier and brute force filtering via 160V low microfarad cap (470 or so).
That unregulated and unfiltered 120V DC then goes into a high frequency chopper..
Chopper output goes into a small high frequency transformer..
Manufacturer now has two ways to go, rectify and filter to DC or allow high frequency AC to go out..
For applications like a simple 12V light bulb, absolutely no reason to add in a few more parts like diodes and filtering to DC..
Old school 12V landscaping lights used a heavy 120V AC to 12V AC 60hz transformer and the output was 12V AC at 60 hz..
Newer landscape lighting most likely has replaced the heavy old school 60hz transformer and replaced with a switching supply..
And I suspect it most likely does not output DC, but AC at the switching frequency..
I HAVE seen this type of setup with indoor low voltage "puck" lights used under cabinets.. The switching power supplies used on many under cabinet halogen puck lights were designed to work with a dimmer and the output was 12V AC at the switching frequency..
Those power supplies typically do not work well with replacement LED modules which have a built in switching regulator (I have been there done that)..
I have a few of those Puck light power supplies laying around, I guess I need to dig one out and check with a meter but I believe that would explain why the OPs lights work but a meter doesn't..
