Could you please check if what I did was righ?

[WildSwan]

This is for my motorcycle' tail light.

The tail light of a motorcycle (or any vehicle for that matter) operates in two modes. 1; used during night time, the tail light is dim and becomes bright whent he brake is used. 2; used at day time, the light is off until brake is used.

My idea is to use LED an have the current regulated. The current will also be used to make the LEDs shine brighter by providing more current when the brake is used.

Here is the diagram...



The current alteration is done by reducing the resistance of the resistor between pin 1 and 2 of LM317. This is done by connecting another resistor in parallel to the existing resistor. This is done by using an NPN transistor as a switch.

So, everytime the brake is used, the transistor is activated. At night time, the circuit still works even if the brake is not used.

My question is, did i do it correctly? It seems to be working but I am open to other idea.

[jacks]

Motorcycle tail light uses two bulb.  Brake light uses higher wattage than tail light. Tail light is tied to headlight bulb. And brake light have separate line.

Tail light only activated with head light switch is switch to on and gets its supply directly form the motors' dynamo. So if your motorcycle have auto head on light it only passby the manual switch.

Brake light gets it supply from battery, not directly from dynamo. You must do some fine tuning/regulation more on tail light for spike since its directly connected to motors' dynamo.

[WildSwan]

Motorcycle tail light uses two bulb.  Brake light uses higher wattage than tail light. Tail light is tied to headlight bulb. And brake light have separate line.

Tail light only activated with head light switch is switch to on and gets its supply directly form the motors' dynamo. So if your motorcycle have auto head on light it only passby the manual switch.

Brake light gets it supply from battery, not directly from dynamo. You must do some fine tuning/regulation more on tail light for spike since its directly connected to motors' dynamo.

Thanks for the info dude. These are extremely useful but my bike's ligthing system is not powered by Dynamo which is commonly called as stator. Mine is Battery powered meaning, all electrical works as soon as I set the key on. Also, tail light of my motorcycle uses single bulb with two filaments inside. You are right that one is higher in wattage than the other.

But the electrical is not so much of my concern right at this moment. I was trying get some feedback regarding the circuit that I posted here... maybe it can be enhanced further?

Just to provide more info, The line that works as a tail light is going to be connected to the L+ line of the circuit. Brake is in the B+ line of the circuit. Ground connects to the chasis. The reason for this is to use LED which last and lights up much quicker than filament.

Thanks.

[WildSwan]

So, walang mali sa circuit?

[jacks]

I cannot see the diagram now, upgrading system namin, mahirap makaconnect. Pero base on your diagram iirc then. Dapat yung voltage adjust mo before lm317 not at 317 output.

Parang lesser voltage, para medyo mahina yung light intensity if your using same LED. Then adjustment is thru some parallel transistor for voltage adjust for more light intensity. Ito ay nakakabit dun sa voltage adjust pin nung 317, pacorrect if mali yung term.

Why not use the straight and simple one using only a resistor on both tail and brake light. But more resistance value on tail light than break light. Or using dull intensity LED and a brighter LED on break light. Pero ito ay may separate line.

[WildSwan]

I cannot see the diagram now, upgrading system namin, mahirap makaconnect. Pero base on your diagram iirc then. Dapat yung voltage adjust mo before lm317 not at 317 output.

Parang lesser voltage, para medyo mahina yung light intensity if your using same LED. Then adjustment is thru some parallel transistor for voltage adjust for more light intensity. Ito ay nakakabit dun sa voltage adjust pin nung 317, pacorrect if mali yung term.

Why not use the straight and simple one using only a resistor on both tail and brake light. But more resistance value on tail light than break light. Or using dull intensity LED and a brighter LED on break light. Pero ito ay may separate line.

Flickering po kasi and madalas, tumataas ang current ng motor lalo na pag mataas ang RPM, sobrang taas na hindi na sufficient ang resistors. Resulta, madali ang buhay ng LED.

[WildSwan]

up ko lang po...

[TinTopHack]

This is for my motorcycle' tail light.

The tail light of a motorcycle (or any vehicle for that matter) operates in two modes. 1; used during night time, the tail light is dim and becomes bright whent he brake is used. 2; used at day time, the light is off until brake is used.

My idea is to use LED an have the current regulated. The current will also be used to make the LEDs shine brighter by providing more current when the brake is used.

Here is the diagram...



2.

The current alteration is done by reducing the resistance of the resistor between pin 1 and 2 of LM317. This is done by connecting another resistor in parallel to the existing resistor. This is done by using an NPN transistor as a switch.

So, everytime the brake is used, the transistor is activated. At night time, the circuit still works even if the brake is not used.

My question is, did i do it correctly? It seems to be working but I am open to other idea.

Something is wrong with your circuit.
1. The voltage at Vadj pin and Vout is kept at a constant 1.25V by the LM317 - so the resistance between this 2 pins MUST be kept constant if you want to control Vout. The current into the Vadj pin must be a few microamps only so changing the resistance value by parallel another resistor will not give you enough current to control the LED brightness. What makes your LED appear brighter when you activate B+ is the current from B+ through the diode > through 1K resistor > through base-emitter of transistor > through 120R - going to your LED.
2. The resistor that should be adjusted is the resistor from Vadj pin to ground - but this resistor is missing.

I suggest you go through the datasheet of LM317 again to see how it should be applied. You have two choices in controlling the LED brightness
- use the constant voltage mode of LM317. I assume this is the mode you wanted to use with your circuit above - You can switch resistor values from Vadj to ground so that Vout of LM317 is switch from a lower value to lower value. In this case you will need some resistor in series with your LED to set the max current.
- use LM317 as a constant current source - In this mode you can vary the resistance between Vadj and Vout but your load must be connected from Vadj pin to ground (effectivley in series with the resistance you are adjusting. In this mode using 2 resistors you can set 2 constant current settings - a low current and a high current value that will go to your LED so that its brightness can be controlled. I would recommend this mode.

[labgruppen]

how about trying this ckt..


it is a simple constant current sink with two reference sources. the tail light supply feeds a lower reference zener (C1 will filter the flicker at low rpm) and the brake light supply will feed a higher reference zener for higher current.

[TinTopHack]

Good idea from labgruppen.

At 5.1V ref for tail lights you get a LED current of around 9.6mA
At 8.2V ref for brake lights you get a LED current of around 16mA

Cheaper pa compared to using LM317.