More LED problems

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Greg_Lewis
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More LED problems

Post by Greg_Lewis »

Electricity had always been a problem for me. I can't see the electrons running around inside the wires, and I've never been able to figure out how it all works beyond volts and amps.

So I installed some LED strip lights in the kitchen. But they blink after they have been on a while. The blink is once about every five or ten seconds. It is a one-time blink, not a flicker. Then a few seconds, and another blink.

Here's what I've got:
- Eight 32-inch LED strips, 21.3 feet total.
- The power requirements for the LEDs is supposed to be 2 amps for 5 meters (16.4 feet). So the total power requirement for 21.3 feet should be 2.6 amps.
- A 5-amp power supply.

As a test, I dropped off all but 5.3 feet of the LED strips, thus needing just under .65 amps, and the strips still blink. Again, it's not a flicker, but a blink every five seconds or so.

I also checked the voltage from the power supply. It is putting out 12.2 volts unloaded. When I load it with all eight strips, the voltage drops to 9 volts. When only two are attached, the voltage drops to 11.4.

The blink is what I might suspect from some sort of thermal breaker inside the power supply but I have no idea if there is one in there. When all 8 strips are attached, the power supply is hot but not too hot to touch. When only two strips are attached, it is not as warm. Below is a pic of the power supply.

So why are the lights blinking? Is there a thermal breaker inside the power supply? Is it the voltage drop? If so, why is there such a voltage drop when the supply is rated 5A and the draw is only 2.6A?

The power supply was sold as a supply for LED strip lights. If the problem is the power supply, what sort of power supply do I need?

THANKS!


IMG_0166.JPG
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Steggy
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Re: More LED problems

Post by Steggy »

Put a meter or, lacking a meter, a compatible light source across the power supply to eliminate it as the suspect. Those types of power supplies usually get warm at full load, but almost never hot, unless grossly overloaded. I would take that 5 ampere rating with a grain of salt.

BTW, are the light strips rated for 12 volts?
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Bill Shields
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Re: More LED problems

Post by Bill Shields »

I would put a scope on the power supply and watch the output...but since you probably do not have one...hook up a car battery to the lights and see what happens.

Does not need to be fancy...just some wire and clips...

It is probably just a defective power supply...but then if they all blink with the car battery connected...well..horse of a different color
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Greg_Lewis
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Re: More LED problems

Post by Greg_Lewis »

Hi BDD:

Thanks for your response. As I wrote above, a meter on the power supply reads 12.2 unloaded and then shows a voltage drop when I add loads. And yes, the lights are rated for 12 volts. They are the common strip lights with three SMD LEDs in a group, with a number of groups per foot to make up the total.

Tomorrow I'll get out the 12-volt battery from the riding mower and see what happens with that. I really suspect the power supply. It's new but that doesn't mean it's OK.

Thanks again.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
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Greg_Lewis
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Re: More LED problems

Post by Greg_Lewis »

Thanks, Bill. Our posts overlapped. No scope but the meter does show that the power supply output does vary by about .1 volt. Will try the battery tomorrow.
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Bill Shields
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Re: More LED problems

Post by Bill Shields »

I would not think that .1 volts causes a problem...some meters are notoriously slow to respond...hence the scope to see what is happening. The .1 volt dip may just be an averaged digital display of a very brief dip of significant value. Digital meters average readings to keep the value displayed from jumping all over the place

A perfect example of this is ripple in a DC supply..that you cannot see on a digital meter, jumps out at you on a scope and can be seen using an old Simpson 360 meter where wou can watch the needle wiggle up and down
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Greg_Lewis
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Re: More LED problems

Post by Greg_Lewis »

Thanks Bill. That's beyond my resources, but what I'll try today is to fetch the battery out of the riding mower, which is new, and see what happens. I'll also check the current draw. Just because the spec sheet gives a rating doesn't mean it's correct.
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Bill Shields
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Re: More LED problems

Post by Bill Shields »

Not sure how you will check current draw unless you have a DC ammeter - which generally requires a shunt ..

Basically you can believe the led listing for current requirements...give it take 100%

I have always been interested in the current capacity of multivolt input supplies.

Is the listed current at the bottom end or top of the input current...or constant no matter what?

So if you add them all up and double it..you are close to what you need from a supply.
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Greg_Lewis
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Re: More LED problems

Post by Greg_Lewis »

Thanks again, Bill.

So I pulled the battery out of the riding mower and hooked it up. The total current draw for all eight 32-inch strips together in parallel as measured by two different multimeters is 3.5 amps. There is no voltage drop or blinking when run off the battery. Therefore we can say the problem is the power supply.

Said power supply shows 100-240V 50-60Hz 1.6A input, with a 12V 5A output. It's a cheap import that I only paid $12 for, so that says something right there.

So the question I'll be asking the supplier of the power supply is whether there have been problems with these supplies or do I just have the wrong one for this job? It was advertised as for LED strip lights and my draw is just over half the rated output, but I have no way of verifying that output rating. It wouldn't even run two strips with a measured draw of .9 amps.
Greg Lewis, Prop.
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Bill Shields
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Re: More LED problems

Post by Bill Shields »

Years ago I would have said go to radio shack and purchase a filament transformer (back when we used vacuum tubes) and a bridge rectifier and put it in a metal box....and forget it for 50 years

I would look for a power supply that is pure 110v in and 12 out to minimize the electronics involved....no voltage regulator which is where I think the problem is located inside your problem child.

Or you could just continue to use the battery and stick a trickle charger on it... :mrgreen:

In general...if you are pulling a steady 3.5 then I would look for a 10 amp or better unit
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Greg_Lewis
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Re: More LED problems

Post by Greg_Lewis »

I, too, miss Radio Shack. Here in Fresno none of the electronics suppliers are left. Even the two that sold primarily to commercial accounts are gone. We have no choice but to buy on line. And then you have to buy a pack of 10 to get one.

I thought about making something up but this one offered plug-and-play. Well, I've played much more than I want to with this. I just wrote to the seller, who specializes in LEDs so we'll see what I get back.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
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Bill Shields
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Re: More LED problems

Post by Bill Shields »

Amazon lists led driver power supplies 100 Watts and over -> 8 Amps is 100 Watts at 12 volts

Suggest something that is 90-130 V input
Too many things going on to bother listing them.
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