LED modul wasting 75% of the energy on purpose!

[Stefan1024]

To illuminate my PC I bougth 10 LED modules with 18 LEDs each (6 packages with 3 LEDs) for 1$ per module.

 

As the polarity was not labled I had to reverse-engineer the schematic. It turned out, that the two resistors (R1 & R2) are only connectd to the power supply and doing nothing but wasting energy. And not a smal amout!

They consume 120 mA out of the 160 mA per module. I desoldered them, and power consumption dropped by 75%. The light output of the module was not affected by this change at all.

By the way, they are brigth and nice. But it tries to trick you into thinking they are more powerful than they really are.

 

So take care when you buy super cheap stuff.

 

 

 

 

EDIT: As @manikyath pointed out, the resistors are required if you power the modul with an old transformer designed for haloge lightbulbs.

But please don't replace you halogen lightbulbs with this modul. Get one that has enougth LEDs so it does use enougth power and doesn't require the resistors.

[thekeemo]

What the fuck..

[DXMember]

put those resistors back on pls, the leds will die out otherwise

the resistors there are to limit the voltage delivered to led, if it's too much (like in your case of removing resistors completely) the led will die pretty soon

[Stefan1024]

Just now, ninninon said:

How many tpyos in one post? Are you typing this on mobile with another mobile by any chance?

No, but I'm native German, doing to much stuff at one time and tired.

[thekeemo]

Just now, DXMember said:

put those resistors back on pls, the leds will die out otherwise

the resistors there are to limit the voltage delivered to led, if it's too much (like in your case of removing resistors completely) the led will die pretty soon

That was my thought too but if that was the case wouldnt they LEDs get brighter by overvolting them?

[Stefan1024]

Just now, DXMember said:

put those resistors back on pls, the leds will die out otherwise

the resistors there are to limit the voltage delivered to led, if it's too much (like in your case of removing resistors completely) the led will die pretty soon

The current limitting resistors are still there (the two smal once on the top).

[DXMember]

Just now, thekeemo said:

That was my thought too but if that was the case wouldnt they LEDs get brighter by overvolting them?

no

the brightness of the led depends on the current

[thekeemo]

Just now, DXMember said:

no

the brightness of the led depends on the current

 

 

[Stefan1024]

Just now, DXMember said:

no

the brightness of the led depends on the current

The current dropp matches exactly.

Two 200 Ohm resistors in parallel @ 12 volts = 120 mA.

[manikyath]

10 minutes ago, DXMember said:

put those resistors back on pls, the leds will die out otherwise

the resistors there are to limit the voltage delivered to led, if it's too much (like in your case of removing resistors completely) the led will die pretty soon

nope, thats the resistors that are connected in series, these are connected in parallel, probably for a very different reason: bad power delivery systems.

 

i'm very slowly making the move from 12 volt halogen, to 12 volt LED. while everything works great in theory, some of the power supplies start to do very weird stuff when they have such a low load attached, and some even go into a failure mode because they think the bulb is dead.

 

EDIT: oh, and marketing, because those two resistors just turned a 0.5 watt module into a 2 watt module.

[DXMember]

9 minutes ago, thekeemo said:

 

 

https://youtu.be/foNi-keKGs4

[thekeemo]

Just now, DXMember said:

https://youtu.be/foNi-keKGs4

? Did you see that happening with Stefans LEDs?

[DXMember]

1 minute ago, thekeemo said:

? Did you see that happening with Stefans LEDs?

yeah but he killed them too fast

also in afrotech description he says that the green led takes yellow color permamently

[Stefan1024]

3 minutes ago, DXMember said:

https://youtu.be/foNi-keKGs4

 

2 minutes ago, thekeemo said:

? Did you see that happening with Stefans LEDs?

 

Not the brightness, nor the color, nor the temperature of the LEDs has changed by desoldering the resistors.

[Stefan1024]

Just now, DXMember said:

yeah but he killed them too fast

 

And they are still working fine.

[manikyath]

Just now, Stefan1024 said:

And they are still working fine.

if you hook them up to a decent power supply you shouldnt face any issues. also, these SMD leds can take more torture than people give them credit for.

 

however, what i wonder is what those 3-pin packages on the back are for. transistor? voltage regulator?

do they have some form of model number on them?

[Stefan1024]

2 minutes ago, DXMember said:

also in afrotech description he says that the green led takes yellow color permamently

And they are white LEDs made of a blue LED with yellow coating.  It convers some of the blue light to yellow to make the light looking white.

They look yellow by default.

[Stefan1024]

2 minutes ago, manikyath said:

if you hook them up to a decent power supply you shouldnt face any issues. also, these SMD leds can take more torture than people give them credit for.

 

however, what i wonder is what those 3-pin packages on the back are for. transistor? voltage regulator?

do they have some form of model number on them?

One is marked with A4: BAV70 diode (two diodes in one package) to protect the LEDs from false polarity.

The other one is maked with A1 and is probably a BAW56 diode (two diodes in one package) , but there are several components with this making.

[manikyath]

Just now, Stefan1024 said:

One is marked with A4: BAV70 diode (two diodes in one package) to protect the LEDs from false polarity.

The other one is maked with A1 and is probably a BAW56 diode (two diodes in one package) , but there are several components with this making.

so.. could i conclude a "whatever is at the shenzen market today" full bridge recrifier?

maybe they're meant to be hooked up to halogen transformers, which legitimately need those two extra resistors in order not to go into failure mode.

[Stefan1024]

Just now, manikyath said:

so.. could i conclude a "whatever is at the shenzen market today" full bridge recrifier?

maybe they're meant to be hooked up to halogen transformers, which legitimately need those two extra resistors in order not to go into failure mode.

The LEDs do not ligth up when I power the module with reverse polarity. So it can't be a bridge recrifier, although the usage of 4 diodes imply this.

 

And yes, the modules are ment to replace a halogen lightbulb. So the resistors migth indeed be needed in this case.

But then nobody should ever buy this modules, as they can't be more efficient than halogen because they need to wast that much energy to be legacy compatible.

[manikyath]

3 minutes ago, Stefan1024 said:

The LEDs do not ligth up when I power the module with reverse polarity. So it can't be a bridge recrifier, although the usage of 4 diodes imply this.

 

And yes, the modules are ment to replace a halogen lightbulb. So the resistors migth indeed be needed in this case.

But then nobody should ever buy this modules, as they can't be more efficient than halogen because they need to wast that much energy to be legacy compatible.

if we conclude the LEDs themselves are around 90% efficient, you're still ~22% efficient with the resistors, where halogen BARELY touches 10%

EDIT: reverse engineer the PCB with the components if you want to, i'll look into it, i honestly think its supposed to be a bridge rectifier, but they soldered it the wrong way or something.

[Stefan1024]

2 minutes ago, manikyath said:

if we conclude the LEDs themselves are around 90% efficient, you're still ~22% efficient with the resistors, where halogen BARELY touches 10%

minus 1.5 volts in the current sensing resistor and 0.7 volts in the protection diode. Also 90% is possible. but I assume they have used very low end stuff here, 80% is more likey.

 

This boils down to an efficiency of ~16%. Reasonable compared to halogen, but terrible compared to other LED modules.

[manikyath]

1 minute ago, Stefan1024 said:

minus 1.5 volts in the current sensing resistor and 0.7 volts in the protection diode. Also 90% is possible. but I assume they have used very low end stuff here, 80% is more likey.

 

This boils down to an efficiency of ~16%. Reasonable compared to halogen, but terrible compared to other LED modules.

if you consider halogen transformers are usually roughly 40% efficient thats still a decent chunk of less power, nothing amazing tho.

 

i'm really curious about the diodes tho.

[Stefan1024]

1 minute ago, manikyath said:

if you consider halogen transformers are usually roughly 40% efficient thats still a decent chunk of less power, nothing amazing tho.

 

i'm really curious about the diodes tho.

Sorry I'm not interested in figuring out how the 18 LEDs are connected. To much work for next to no benefit.

[bob345]

I would be willing to bet that those resistors where there to keep the computer in some cars happy. In some  cars, mostly German,  you will get a warning light/message that a light has burnt out if the correct amperage is not being drawn.