Resistor Value Calculation for 5x 5050 SMD LED Car Bulb Replacement

Question

I replace the bulbs in the car with LEDs and some of them, unfortunately, do not have a resistor, which causes them to go out immediately. Such a bulb has 5 5050 SMD LEDs. I count well? The resistor for one should be: 420 ?? and times 5 now?

Grzegorzm2121 · Accepted Answer

Since the resistor is to lose 3W power, using a resistor with a lower power will burn it.

Anonymous · Accepted Answer

With this resistor value, you lose 0.25W on it. The resistor itself is ok because it has a cermet housing but it may not be enough to cheat the CAN. It may turn out that you need 8 resistors connected in parallel. It all depends on how sensitive CAN is. Experiment a little with the resistors and you will see at what value it will be ok. He adds: You also have in this store Such a thing ready for 5W5 . There is a 50 Ohm resistor with a power of 15W. And you lose 2.88 W at 12V on it. But at 14V you lose 3.92 W on it

Anonymous · Accepted Answer

I would start with a 100 Ohm resistor (maybe even 150 Ohm) in parallel to the bulb. for the time of testing, it can be of lower power, e.g. 0.5 W If it will be ok, leave it only with more power. You can calculate the resistor power from P = U * U / R Take 14V as U (normal voltage for normal operation). AR is the value of the resistor in ohms. You won't have to move the CAN then

Grzegorzm2121 · Answer

You gave no tension or efficiency to the source but by reading the tea leaves I can tell you did it wrong! (kidding). First, state the voltage of the source, maybe the current efficiency and the type of bulb.

jas2010 · Answer

I bought exactly these bulbs.

Grzegorzm2121 · Answer

It looks like these bulbs are specially made for cars so you don't need resistors unless you have a 24V battery. It is strange that they are going out, maybe you have a wiring diagram in the car?

jas2010 · Answer

In the car, the canbus system checks the bulbs and it seems they do not fit. I will look for a diagram in a moment, skoda octavia estate 2, 2007. Added after 3 [minutes]: Diagram: This is how we put attachments on the forum! [_P_]

Grzegorzm2121 · Answer

These bulbs are where do you want to install?

jas2010 · Answer

I want to set up as positional.

Grzegorzm2121 · Answer

I found a problem! These bulbs you install have 3W and the car bulbs should be 5W so they probably burn out. See in the drawing a circle with a cross near the word parking.

Molejnic · Answer

What do I have the power to burn out a light bulb? 3 or 5 watts is a question of power consumption. I would bet more on the problem of polarity or the fact that they have too little power and the car's computer turns them off because it treats them as burned. You would have to make sure if they were burnt or just not lit.

Grzegorzm2121 · Answer

Can you check how many volts there are in the socket? Also check the current (only in series!) With a 10k resistor, we'll see if the voltage is constant. Also check the fuses. And if the car has a computer, it's bad because it is not known how it will react to these bulbs. Can you see them on some other power source, do they work?

jas2010 · Answer

They are not burned, they go out because the computer disconnects them. On the back of the car I have 4 positional LEDs and the LEDs work in a combination of 2 LEDs +2 standard T10 Added after 43 : The bulb according to the manufacturer is 4.2 W

Grzegorzm2121 · Answer

Maybe it is due to the resistance of these bulbs (too big or too small) you can get around the computer but it's difficult and risky. Maybe you need to give some resistor to confuse the computer.

jas2010 · Answer

exactly, from the beginning, I am asking you to calculate the resistor, the formula gives me strange values

Grzegorzm2121 · Answer

How do you count it? Because I too had problems with complicated layouts. You have to count every single resistance in the circuit so it will be difficult. And you also have to take into account everything that the bulb has inside, so it's a bit almost a miracle.

jas2010 · Answer

In the calculator, for 1 white diode it comes out: The resistor should be: 420? Resistor power required: 168mW and for 5 diodes I have a message: This will not work - the supply voltage does not exceed the forward voltage of the diode (s)! Added after 1 [minutes]:

vodiczka · Answer

If these are 12V LEDs, they have a built-in resistor or current limiter. What other resistor do you want to choose?

jas2010 · Answer

And they don't have little resistance and the computer (Canbus) sees them as blown and then cuts off the electricity? I see it that way. I will summarize what I know about the light bulb: 4.2W power Voltage 12V Max forward current 60mA white color - about 3.6 V per diode (there are five)

Anonymous · Answer

According to the link provided by you, this LED bulb draws a power of 3W. You should have a 5W load for CAN. So you do this: You connect this LED bulb (YOU WILL NOT CHANGE NOTHING IN IT) in place of the old bulb. From the side of the plug you connect an additional resistor PARALLEL. Since you have to lose 2W on it, this resistor should be at least 3W (preferably 5W) and should be 75 Ohm. The resistor will be warm. And that's all.

mendozek666 · Answer

Hello It seems to me that the problem with these leds is caused by one integrated circuit that is located in the comfort module or the BSI module. I did this recently in my car. After inserting all the LED bulbs inside the car and in the trunk, after closing the car with the remote control, the bulbs glow a little. The voltage measurement in this case is around 6-7V. I replaced one bulb with an old tube one and it's ok. Now all goes out to zero. I will add that in my module it is the U4791B chip and it is probably called a car lamp failure monitor or something like that. The system checks the set current consumption threshold, and after replacing ordinary lamps with LEDs, it is probably smaller, so problems with possible errors or turning off lamps with LED bulbs. Regards

jas2010 · Answer

it makes sense the same bulb has more on this page for 12V there is no 0.25W resistor? I read something somewhere, but I might be wrong Added after 3 [minutes]: maybe that would be enough

jas2010 · Answer

You did not understand, it was supposed to be for my friend mendozek666 what should I check? 1W and How Many Ohms? I care about the safe work of the light bulbs, Canabusa will finish cheating with Vag (the indicator of the burnt bulb) Added after 4 [minutes]: filter price PLN 20

vodiczka · Answer

Friends. What is the point of replacing an ordinary light bulb with an LED and then inserting a resistor (deceiving computer) that uses the battery energy uselessly? It is like replacing light bulbs in an apartment with energy-saving ones and turning on a small heater constantly

jas2010 · Answer

I replaced the low beam with a decent 50W kit. CREE and there is too much contrast between them. I admit that there is much greater visibility on Ledy. All glare on the road, signs. Overall a more enjoyable drive

vodiczka · Answer

The topic is about parking, not passing.

jas2010 · Answer

Lists the reason for the positional swap.

jackins · Answer

Hello, I connected the LEDs without the module - 3 cables from lamps + and - and + control room. + control connected to the parking lamp - connected to the akku. + after the ignition switch to the ignition module in the cabin under the glove box. Unfortunately, they don't work properly. After turning the key, the LED lights are ok. After starting the engine, it is also ok. Unfortunately, after turning on the lights, the LEDs do not go out but they dim and blink or light up: / Parking light bulbs are not LEDs ... well, maybe LEDs are behind if it has meaning. Where is the devil sitting? Link to (probably exactly like mine): Link removed / trimmer01

Zdzisław1980 · Answer

Shouldn't this control be connected to the + dipped headlamps? I am ignoring the fact that it has nothing to do with this topic. We write about something else here.

Resistor Value Calculation for 5x 5050 SMD LED Car Bulb Replacement

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