[quadra]

I recently installed LED turn signals at the rear however they are blinking too fast at turns. Hazard light blinking is still at the standard speed.

I came across this article which tells how to fix this however i have no clue how to proceed.

Link: https://www.superbrightleds.com/blog...Hyperflashing)

Can someone translate it a simple language?

Cheers.

[ZBlue]

Originally Posted by quadra

I recently installed LED turn signals at the rear however they are blinking too fast at turns. Hazard light blinking is still at the standard speed.

I came across this article which tells how to fix this however i have no clue how to proceed.

Link: https://www.superbrightleds.com/blog...Hyperflashing)

Can someone translate it a simple language?

Cheers.

LED's draw much less current than filament bulbs. A standard 21W turn signal bulb will draw approx. 1.75 amps of current at 12V. A LED turn signal will draw a lot less , usually less than .5 amps. This causes the BCM to think that a light is out and causes the hyper-flashing.

Two ways to get around this :

1) You can use a turn signal flasher specially designed for LED modules. I don't think these are readily available for most Indian car models.

2) You can fool the computer into thinking that the original bulb is still there. Again , two ways of doing this. You can wire the original filament bulb in parallel with the LED. Since the LED's draw little power , the total consumption of filament+LED should still be well within limits.

Or you can use load resistors as the website states. Load resistors are basically like dummy bulbs which draw power (and get hot) without emitting light.

Using the numbers I put above , if the original bulb draws 1.75 amps and the LED's draw .5 amps , you need to account for 1.75 - .5 = 1.2 amps.

Using Ohm's law (V = IR) , this 1.2 amps corresponds to 12/1.2 = 10 ohms. So you would need a 10 ohm load resistor. Since it is replacing a 21W bulb , you would basically need a 25W (or 50W) load resistor rated at 10 ohms. This would again have to be wired parallel to the LED's.

I got them from here :

http://www.digikey.com/product-detai...0R0-ND/1646182

Note that the load resistor should ideally be mounted on metal to better dissipate heat , but for turn signals it shouldn't be a big deal.

[audioholic]

From an electronics students point of view, LEDs dont work well without a resistor that limits current to them. By work well, I mean to say work in a practical, safe and as per required manner. I guess the bulbs you installed are not coming with an inbuilt resistor or the resistance is too less.

Direct fix - Introduce a resistor in the loop. Which resistor? That needs some math. Anyways if you could give further details about the bulb maybe I can tell what resistor to use.

Why resistor?
The normal bulb(one with filament) is a resistor in itself. The conventional flashers work in this way which I will explain in the simplest way I can - After X amount of current passes through the circuit, the flasher cuts off and after some time it will turn on again. Thats how the indicators flash. More resistance is less current. Hence the old bulbs offer a resistance, and due to that, the X amount of current takes a longer time to pass through the flasher.

With LEDs one annoying thing about them is, as they turn ON, their resistance almost becomes Nil. This means any amount of current can pass through it as it turns on. So the X amount of current that the flasher allows before it cuts will pass a lot quicker, thus making the flashes seem very quick. By adding a resistor, you will effectively lessen the current passing through the circuit and the flasher will keep the bulb ON for a longer time. Another advantage of adding the resistor is with a minute reduction in brightness of the LED, the life of the bulb will greatly increase. Hence, the key to using any LED is by controling the current that it handles externally, since it cant regulate that on its own.
Hope this was useful, else consider this as some sleepless thought I had

EDIT: Didnt see the above post. Sorry for duplicate content if any :P

EDIT 2:

Originally Posted by ZBlue

LED's draw much less current than filament bulbs. A standard 21W turn signal bulb will draw approx. 1.75 amps of current at 12V. A LED turn signal will draw a lot less , usually less than .5 amps. This causes the BCM to think that a light is out and causes the hyper-flashing.

.

I dont think thats the reason. If the light draws very less current why will the BCM flash it faster? It should actually flash slower going by your logic since it will try to provide greater current if possible. Rather the BCM will throw up a short circuit error and thats why the CAN BUS compatible accessories are used. The reason is what I have explained above. Whereas the conventional bulbs are driven by voltage sources, LEDs must be driven by current cources. The BCM acts as a Voltage source. When you connect an LED to it, it will not let the 12V supply from BCM be like that. Since it has no resistance of its own, there will be a lot of current drawn MOMENTARILY which will cause the BCM to cut off and throw a short circuit error.

As you said, LEDs draw a fraction of current compared to an incandescent lamp, however it should be driven by an appropriate driver which is the common Led drivers we see. If the current is not controlled, it can draw excessive current and eventually burn out after some time.

[ZBlue]

Originally Posted by audioholic

....
Direct fix - Introduce a resistor in the loop. Which resistor? That needs some math. Anyways if you could give further details about the bulb maybe I can tell what resistor to use. ....

Originally Posted by audioholic

Another advantage of adding the resistor is with a minute reduction in brightness of the LED, the life of the bulb will greatly increase. Hence, the key to using any LED is by controling the current that it handles externally, since it cant regulate that on its own.

I think you are assuming that OP is using an LED without any resistors which is probably not true. The LED being used probably has the appropriate current-limiting SMD resistor already built in.

Originally Posted by audioholic

I dont think thats the reason. If the light draws very less current why will the BCM flash it faster? It should actually flash slower going by your logic since it will try to provide greater current if possible. Rather the BCM will throw up a short circuit error and thats why the CAN BUS compatible accessories are used. The reason is what I have explained above.

With my limited knowledge , I remember reading somewhere that the "hyper flashing" is actually a positive action taken by some IC somewhere to actually alert the driver that a bulb is out. This seems a plausible explanation , given that you would get the hyper flash even when there are no bulbs connected at all.

Originally Posted by audioholic

As you said, LEDs draw a fraction of current compared to an incandescent lamp, however it should be driven by an appropriate driver which is the common Led drivers we see. If the current is not controlled, it can draw excessive current and eventually burn out after some time.

You are right , but LED drivers usually come into play only when using high-powered LED's (driven at 100mA and above). In most other cases , I usually regulate the voltage at 12V and fix the current draw by using the appropriate current-limiting resistors.

[quadra]

Originally Posted by ZBlue

Two ways to get around this :

1) You can use a turn signal flasher specially designed for LED modules. I don't think these are readily available for most Indian car models.

2) You can fool the computer into thinking that the original bulb is still there. Again , two ways of doing this. You can wire the original filament bulb in parallel with the LED. Since the LED's draw little power , the total consumption of filament+LED should still be well within limits.

Or you can use load resistors as the website states. Load resistors are basically like dummy bulbs which draw power (and get hot) without emitting light.

I got them from here :

http://www.digikey.com/product-detai...0R0-ND/1646182

Note that the load resistor should ideally be mounted on metal to better dissipate heat , but for turn signals it shouldn't be a big deal.

Originally Posted by audioholic

Direct fix - Introduce a resistor in the loop. Which resistor? That needs some math. Anyways if you could give further details about the bulb maybe I can tell what resistor to use.

Thank you guys for replying to this thread. I am still confused on where do i begin to fix this issue. The solutions mentioned above are logical however doesn't help. If its that complicated to fix, i would rather move on.

Do we have anyone here who switched to LED turn signals? & facing this problem?

[audioholic]

Originally Posted by ZBlue

You are right , but LED drivers usually come into play only when using high-powered LED's (driven at 100mA and above). In most other cases , I usually regulate the voltage at 12V and fix the current draw by using the appropriate current-limiting resistors.

Yes sir, but by adding the current limiting resistors, you are indirectly driving the LEDs right? By driving I didn't mean to say high oower circuits. To make it simple I used the term

The LEDs may have a resistor inbuilt, but as I have told in the previous post, it may not be sufficient. Maybe the resistor value used is such that ot allows the max current that the LED can handle. Instead if we reduce this a bit, we could achieve longer flashes.

[ZBlue]

Originally Posted by quadra

Thank you guys for replying to this thread. I am still confused on where do i begin to fix this issue. The solutions mentioned above are logical however doesn't help. If its that complicated to fix, i would rather move on.

Do we have anyone here who switched to LED turn signals? & facing this problem?

It's quite simple really. You need to add some extra resistance to the circuit. To begin with why don't you tell us what LED's you are using for your turn signals now.

Using load resistors is a popular way to fix the hyper flashing. I plan to use it myself shortly

Originally Posted by audioholic

The LEDs may have a resistor inbuilt, but as I have told in the previous post, it may not be sufficient. Maybe the resistor value used is such that ot allows the max current that the LED can handle. Instead if we reduce this a bit, we could achieve longer flashes.

You are saying that by reducing the current (by using a larger resistor for the LED) we can get longer flashes ?

[Ahmed]

Replace the regular flasher by an LED one. This should clear the flashing error. They are readily available with aftermarket stores these days. Fiem is a famous brand in this.

[sohail99]

I had converted to full LED turn signals and had to replace the stock flasher with LED one for them to work properly. - http://www.team-bhp.com/forum/techni...-tricks-4.html

Using resistors to fool the stock flasher (by consuming similar loads as incandescent bulbs), is a waste of low power consumption advantage(as well as lower strain on battery and electrical system) of LEDs.

[ZBlue]

Originally Posted by Ahmed

Replace the regular flasher by an LED one. This should clear the flashing error. They are readily available with aftermarket stores these days. Fiem is a famous brand in this.

Originally Posted by sohail99

I had converted to full LED turn signals and had to replace the stock flasher with LED one for them to work properly. - http://www.team-bhp.com/forum/techni...-tricks-4.html

Using resistors to fool the stock flasher (by consuming similar loads as incandescent bulbs), is a waste of low power consumption advantage(as well as lower strain on battery and electrical system) of LEDs.

Completely agree. As I wrote earlier , the ideal solution would be to replace the stock flasher relay. But in my Linea , apparently the flashing is controlled by the BCM itself and said relay does not exist , at least according to FASS. Which is why I need to use load resistors.

[VinodDevil81]

Originally Posted by ZBlue

With my limited knowledge , I remember reading somewhere that the "hyper flashing" is actually a positive action taken by some IC somewhere to actually alert the driver that a bulb is out. This seems a plausible explanation , given that you would get the hyper flash even when there are no bulbs connected at all.

Sorry, but I did'nt really get that point.
How can one get hyper-flash or any flash, when there are no bulbs connected at all?
Did you mean to say when one of the bulb pair is disconnected?
Like say, the front left indicator may hyperflash, if the rear-left indicator bulb is out? I have noticed this happening in 2-wheelers.

[anuragn]

Originally Posted by VinodDevil81

Like say, the front left indicator may hyperflash, if the rear-left indicator bulb is out? I have noticed this happening in 2-wheelers.

Exactly.
This is what happened in my WagonR a few days ago. It was this hyper-flashing that lead me to discover that one of the three (i.e. front, front-left & rear) indicator bulbs had gone kaput.
So I think it is a feature by design to alert about a fused/missing bulb.

Now coming to theory:
LEDs draw very small amount of current compared to filament bulbs. Which means LEDs present a much higher resistance. The controller is tuned to detect a fused/missing bulb when it encounters a very high (i.e. infinite) resistance, meaning an open circuit. The threshold value of activating open circuit error must lie somewhere in between the resistance of a bulb and that of LED. Hence, the presence of LED actually fools the controller into thinking that bulb is missing.
Also, adding a resistor in parallel may solve the hyper blinking, but will defeat the very purpose of LEDs i.e. power saving.

[56landmaster]

Well for me LED's purpose is primarily greater visibility due to greater output without fraying wires due to increased power draw.

Power benefits from rarely used components such as indicators is too crazy for me

[::CMS::]

Power saving in car? How much can a turn indicator save?

To me its a waste of time and money. I agree, LEDs will be brighter than normal bulbs. But adding a load resistor to prevent BCM error will make the LEDs to look almost same as the normal bulb (not same, but with a slightly sharper light). Moreover, unless the reflectors are not designed for LED lights (like in Merc or other similar cars), these LEDs will be difficult for the other users esp led brake lights in a traffic.

In bangalore a lot of the taxi cabs have made a mockery of their rear end lights by using different coloured leds and that too blinking ones, are very irritating to the eyes and more over it is dangerous as other lights than red / amber color will have less travel.

[audioholic]

Originally Posted by anuragn

Exactly.
Now coming to theory:
LEDs draw very small amount of current compared to filament bulbs. Which means LEDs present a much higher resistance.
.

Can you explain how an LED will present a higher resistance? D
It is a diode, which in forward bias has a minute resistance, and ideally a short circuit.