The presented circuit of a DRL or a Day Time Running Light was requested by Mr.Senthil. Let's understand the complete design.
The Circuit Request
I'm an avid DIYer. Recently, i was looking to make a DRL(daytime running light) for my car using 1 watt smd LEDs.
But i couldn't find an appropriate circuit for my need. I want to drive Eight 1watt LEDs from my car battery.
I would very much appreciate if you could design a simple and rugged circuit to drive 8 x 1watt leds from a 12-14v input.
I'm also planning to add a heat-sink to dissipate any heat generated by the leds.
Thanks & Regards,
The Circuit Design
What's a DRL or Day Time Running Light Device:
A DRL is a safety car lighting device specifically assigned to moving vehicles for increasing the conspicuity of the vehicle during day time, especially when the daylight is accompanied with fog or during dull overcast days.It is normally fixed just beside the headlamps on either sides.
Normally a DRL system is in the form of constantly illuminated high intensity lamp. With the advent of modern High intensity LEDs, making a DRL lamp is matter of less than an hour.
As per the request the proposed day time running light or DRL circuit would be in the following form:
However in case you are interested to spice up the above idea a bit, and think that the system should do justice to the name that it has been specified, you would want to make it a literally "running" or chasing kinda thing!
Making a Chasing DRL Circuit
The DRL circuit discussed below shows how we can add a running effect to the above design and make it further interesting.
The circuit is actually a straightforward powerful LED light chaser circuit which is able to drive many 1 watt LeDs in a sequential manner.
The IC 4017 is a Johnsons Decade counter which generates a sequential switching at its 10 outputs in response to positive pulses fed at its pin#14. These pulses are referred to as clock signals.
As can be seen in the given circuit diagram, the IC 555 is configured in its basic astable multivibrator mode, and generates the required clocks for the IC 4017.
The clock pulses are taken from pin#3 of the IC555 and fed to pin#14 of IC4017.
In response to the above clocks, the output of the IC 4017 shifts a high logic sequence from pin#3 to pin#6. The moment it reaches pin#6, the sequence reverts to pin#3 and the cycle repeats.
Since only 8 LEDs are requested, pin#9 is connected to the reset pin of the IC so that the only 8 outputs become active with the required functions.
The speed at which this sequence may "run" or "chase" will depend on the setting of the 100k pot. Any value between 1 to 5 Hz may be set by suitably adjusting the pot.
The transistors respond to the sequencing high pulses at their bases and switch ON the connected 1 watt LEDs in the same pattern creating a powerful dazzling "running" LED light effect.
Since the illumination is very powerful, would become visible even during daytime and on foggy days and thus the circuit becomes very suitable as a DRL unit and may be used in cars as a Day Time Running Light device.
Chasing Dark Spot LED DRL Circuit
For creating a "running dark spot effect" use PNP transistors in place of the NPN ones, connect the emitters to the positive, and connect the LEDs across the collectors and ground. Do not forget to reverse the LED polarity too.