Lowes 12VAC LED Landscape Lite--->12VDC Boat Lite...Voltage Regulator Question

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1

Greetings All,

I stopped by Lowe’s recently and saw an interesting LED 12VAC landscape floodlight on clearance…

here…

I thought it could make a dandy light for use on my small boat, for avoiding crab pots and other
miscellaneous hazards.

The package states “14 watts” and “1100 lumens”. Inside the aluminum housing, there’s a
small board with a bridge rectifier and an MP2480. It was putting out 6VDC to the LED array.

Apologies for not getting the pics to appear here…clicking the pic icon seems to open them up,
on Flickr.

I had several eBay LM2596 voltage regulator boards laying around, and hooked one up,
set to supply 6VDC…

It works great—for about 15 seconds! Then, the LM2596 heats up, and starts blinking
the LED array.

I’ve got a couple of questions here, in trying to figure out what’s not right.

1. The propaganda on the eBay voltage regulator board suggests it’s good for up
to 3A without heatsinking or other heat-abatement; the Lowes carton describes the
LED lamp as ‘14 watt’, or about 2.4 amps at 6VDC. So, nominally—given figures of
possibly dubious validity—the eBay board sounds like it could supply the LED array.
Do I just need to add a heatsink to the existing board, or get a board with higher
amp capabilities?

—and—

2. I understand LEDs require some type of limit on current; with the resistors mounted
on the LED array, is the current-limiting issue taken care of (or do I need to use a voltage
regulator board that provides ‘constant current’ control)? Is the LED array trying to pull
way more than 2.4 amps from the eBay board?

Thanks for comments, criticisms, suggestions, etc!

2

I think what is happening is that as the LED is heats up, it will draw more amps, until the LM2596 board is not able to deliver what the LED “asks” for. You need a constant current driver, not a constant voltage driver. Here is a YouTube video of what happens when a constant voltage source is used to drive an LED. I used that very same board that you are using.
I know you think what you are witnessing is caused by the LM2596 board heating up. Although it is heating up, it is not it heating up that is causing what you see.
From Left to right the 4 meters display source voltage, current draw, LM2596 temp and voltage to the LEDs
Notice that as the LM2596 heats up, the voltage to the LEDs remains constant but the current goes up.
That is caused by the LEDs heating up. (I did not measure that temperature).

3

I’m not completely clear on the details.
May I ask what kind of power source you are now using for the LM2596 input?
Any special reason you are not using that MP2480 board anymore besides the fun of tinkering around? :wink:

4

Thanks, dchomak, and Neat test set-up!

If I go with a constant current driver, how would I figure out the correct amperage for this array? I understand
‘too much’ current will kill the LEDs.

BTW, not to side-track my own thread :stuck_out_tongue: —on your vid, the LM2596 heated up steadily to about 220*, around 3:40, but then tapered
back down to just over 200*, and seemed to hold that for the duration. What was going on there—some kind of ‘soft’ self-protection?

I assume mine was self protecting from over temp, but it was completely turning the LEDs off…initially at a slow rate, but faster over the
the five seconds or so that I kept everything running.

5

Hi Dave,
The assembly was powered by my boat’s 12VDC system; standard marine lead acid battery, with outboard
motor alternator charging, when outboard motor is running. While I was testing the assembly, it was just
being powered by the battery.

I thought about using the OEM MP2480 board by tieing the boat 12VDC into ‘backside’ of the bridge rectifier,
but I had several of the eBay LM2596 boards on hand, already. Also, I looked up the specs on the MP2480
and they sounded very similar to the LM2596. Now I’m wondering if that board is set up to give a constant
current output…hmmm.

6

Yeah, they are quite similar in many aspects. The MP2480 was made with a constant current source in mind though. (low feedback voltage, different control behavior)
It probably was used as a current source, and with the feedback resistor’s value we could figure out to what current it was set.
No matter if you want to use the board or not, that’s a good thing to know. :wink:
Maybe you could take a photo of the board? :slight_smile:

7

Yessir!!

Here’s the main overall view of MP2480 board:

This is underside…between the caps, a copper foil board
for heat:

Here’s a close-up of components around the MP2480:

Edit: this was the OEM board supplied with lamp, for use on 12VAC ‘low voltage landscape lighting’.

8

That’s what I thought when it first happened, but what I really think happened was, if you will notice at the very end, the yellow plastic clamp popped off. That was clamping the thermo-couple to the heatsink of the LM2596. At the end it got so hot it melted! I believe the thermo-couple was loosing the physical connection to the sink at that point.

The 2 LEDs that it drives were hooked up in series. Even though there is initially thermal runaway here, I decided to use this circuit as is. The reason being is that LM2596 has built in current protection of about 2.7A. In effect I am sort of using it as a constant current supply once it max’s out. Crude but it works for me.

In your case the flashing could be some sort of interaction between the LM2596 and the driver in your light. Remember, my lights have no internal driver. They are running direct drive.

9

Ah so! It was measuring ‘near ambient’ instead of actual component.

All I see on my LED panel are the 14 LEDs (!), 14 resistors, and two caps…no IC’s.

10

Thank you! :slight_smile:
It is set to 1.8A. That makes 125mA per chip, sounds reasonable for those LEDs.
Those resistors are to symmetrize the current between the LEDs, not to limit overall current. There are a little low in resistance for that.
Keep that in mind when testing other voltage sources. :slight_smile:
(Now I can see the lamp actually. My other browser did now show the pics, not even symbols. )

11

Ok, 1.8A…the MP2480 could easily supply that.

When I put a 12VAC wall wart as a source to the board, it was showing 6VDC out to the LED array. Would I be
correct in assuming I should set the output on (whatever) board I put in, to 6VDC out—?

I think I set the output voltage on the LM2596 without the LED array connected. Hmmm…maybe I should have
adjusted it to 6VDC, with the LED board in circuit (I’m not skewl-trained at this :Sp )?

*EDIT: Correction on my thinking, here—the LM2596 board should put out the same voltage, with or without
load. However, the MP2480 is putting out constant current. Would I be asking for trouble, if I adjusted
the LM2596 up to the unloaded MP2480 voltage? The MP2480 was showing something over 11VDC out, with
no load.*

I apologize for my sub-par graphics embedding! I tried multiple techniques on the board and from Flickr, and
the ‘clickable icons’ were the best result I found. I’ve embedded pics on other forums successfully, and even
read the FAQ…shrugs

12

Those UF 502B heads, you have a P60 drop-in inside…did you wrap with foil to wick the heat away from the pill?

Also you need constant current not constant voltage to LED emitters, as LED emitters heat up they draw more current making more heat drawing more current making more heat drawing more current

I recommend getting 12vdc drivers…you can find them pretty cheaply here
something like these
http://www.fasttech.com/products/0/10001419/1110706-12v-1x10w-high-power-constant-current-led-driver

And/or get some of those buck dc/dc power converters and have them step down 12vdc from the battery to 4.0~ vdc and then just use the lights stock driver
http://dx.com/p/produino-100w-dc-dc-10-32v-to-60-97v-boost-converter-charger-module-red-black-282973

P.S. You have to put some pretty heft heatsinks on those voltage regulators, when you pull alot of current thru them…they get hot pretty fast!

A. On the pills do you know if the LED’s are on copper stars (hotter they get the more current they pull)
B. Is the P60 Drop-ins aluminum foil wrapped to help wick the heat away (not going to help much as there isn’t alot of “meat” to dissipate the heat
C. Is the regulator attached to a heatsink (as you see from the above 100W module they have pretty heft heatsinks, those smaller modules don’t have heatsinks and as you see they get hot

13

Whoa! You lost me at ‘UF’… :party:

14

In the above videos, the black things the light is being pushed…is UltraFire 502b flashlight heads (minus the battery tubes of course), they use P60 module dropins (not trying to insult your intelligence)

http://www.fasttech.com/product/1409307-ultrafire-wf-502b-led-flashlight-host

P60 drop in module
http://www.fasttech.com/products/0/10002212/1159800-cree-xm-l-t6-10w-led-drop-in-module-265mm

Those smaller DC-DC converters can only push a few amps output…gotta heatsink those regulator chips if you want to push the power above a few amps
http://dx.com/p/lm2596-dc-to-dc-voltage-reducing-converter-circuit-board-deep-blue-295915
Fasttech one is a buck cheaper
http://www.fasttech.com/product/1253701
Bucking regulator
Output adjustable via potentiometer
SANYO solid state capacitors
3A maximum current draw

15

Ohhhh…gotcha! :bigsmile:

That wasn’t my vid. :wink:

16

Probably just heatsink the snot out of the regulator chip, if it pushes that led from the original link but just get’s hot…then you need to either heatsink it, or get a bigger more capable DC-DC converter

Remember we are talking Chinese AMP and Lumens…they claim 3A but due to inefficiencies and whatnot…well you may not get what they “claim” :smiley:

Oh yeah…include one of these little puppies with your volts regulator…just solder in on the “output” posts…voila…instant variable power supply with display
http://www.fasttech.com/products/0/10002968/1222902-036-display-3-digit-330v-voltage-tester-for-18650-
(little arrow next to “buy now” button shows the different colors they have

Adjust regulator to supply voltage, not load voltage…

MP2480 is a step-down switching regulator that delivers a constant current of up to 3A to high-power LEDs

Says it’s 95% efficient…but I wouldn’t believe that…if it claims it can push 3A, you have to push MORE into it…so it’s probably pulling 4-5A from that little board…this is probably why it’s getting hot
• Wide 5V to 36V Operating Input Range
• Up to 95% Efficiency
• Hysteretic Control with No Compensation
• No Output Capacitor Required
• ±3% LED Current Accuracy
• Up to 2MHz Switching Frequency
• Up to 20kHz Dimming Frequency
• 200mV Reference Voltage
• Short-Circuit Protection with Integrated High-Side MOSFET
• Thermal Shut Down
• Available in SOIC8-EP

Looks as if you can plug it straight into a 12vdc power source…aka tie is straight into the battery

17

I got my light working correctly…

Went back to the OEM MP2480 board…hooked it up to a 12VAC wall wart, probed the
output side of the bridge rectifier, and found the 11.xx VDC output. I wired the boat’s
12VDC to that location, and hooked it up to the LED array…

Ran it for 12 minutes continuously. The LED board and aluminum mount plate got
plenty warm, but no blinking or smoke.

Lessons Learned:

  1. LEDs are suicidal, they’ll try and eat more amps than is healthy for
    them, if allowed. :open_mouth:

2. Don’t desolder leads from a board that may possibly be reused, especially
if solder points are only about 1mm apart…just snip the leads long enough,
to solder to later, if needed. :expressionless:

18

same thing i do to the cheap mr16 drivers.remove the bridge to save 2 diode drops and run from +12
with only 2 led’s yours will run down to around 7.5v so no biggie.i run 3 rebels or k2 tffc series so removing the bridge gives a bit of headroom.high is good.better efficiency.so dont worry about going high.i tested mine to 20v and it just dropped current on input and ran cooler.

19

Hey Snakebite,

Yes, I did in fact go back to the OEM 12VAC driver board…attached 12VDC on output side of rectifier, and it did work. I didn’t feel comfortable with the wiring connections to the board, however (this will be mounted on bow of a 15’ boat, subject to quite a bit of physical jolting). I found this critter on eBay, constant current/constant voltage—

http://www.ebay.com/itm/201003157037

It had me scratching my head for a while; didn’t realize the module runs constant current OR constant voltage, one or the other, but not both at the same time.

I set the new module (in constant current mode) at .99A. The LED array is still blindingly bright in daylite, and it got up around 125*F according to my Harbor Freight pyrometer…not near as hot as what the OEM module was getting it (too-hot-to-touch range; didn’t think of using pyrometer unfortunately). It will possibly get quite a bit warmer when the lamp housing is assembled and the LED array is fully enclosed.

The XL4005 on the new module did not discernably warm to touch, after 20 minutes; the inductor was barely warm to touch.

Hopefully I’ve got a light that will last a good long time. Can’t wait to get out on the water for some night fishing, and see how much this light will help in navigation!