The post discusses the construction chasing car tail light circuit using high bright 1 watt amber LEDs. The idea was requested by Mr. Brian Walton.
I've been giving the project some further thought. I am wondering what changes might be needed to use single, higher power leds instead of the advised 5mm ganged in threes? So there would be 6 LED's rather than 6*3 5mm
The reason is that I have combined LED DRL & indicators on the front of my car, so I would like to retain the OEM look & feel at the rear - where I propose to use your excellent circuit design.
I'm thinking along the lines of the LEDS in the link below.
They are Osram Opto Diamond DRAGON Series GW Amber LED. They are designed for automotive use in DRL's and indicators.
They are 2.9v forward voltage and appear to take about 1.4A at typical lumens.
The LEDs above are not definitive but a suggestion in terms of output and style for my construction needs.
So my question is can the circuit take or how do I need to modify the circuit to take the extra power these LED's may take.
For info; from a practicalities point of view, I intend to have a separate driver circuit for each side of the vehicle - it makes installation simpler given i'm going to attach the pulse form the existing indicator
relay as discussed previously with you.
I hope you can advise me (again!) and many thanks for your devotion to the electronics hobbyist on the web.
Solving the Circuit Query
Incorporating higher wattage LEDs will need individual transistor buffers across the 6 outputs from the IC, it's actually very easy to implement.
I'll try to explain the connections verbally, although I am also thinking of updating a suitable diagram for this particular application, I may do it within a couple of days....in the meantime you could try doing the following mods in the above circuit:
Use TIP122 for the buffer transistors.
Connect the bases of the 6 transistors to the respective outputs of the IC 4017 via the indicated diodes. Make sure the base have individual series 1k resistors
The LEDs will need to be attached across the transistor collectors and the positive, the LEDs too must have their own series limiting resistor
The LED resistors could be calculated using the following formula:
R = (Us - LEDfwd)/I
where Us is the supply voltage,
LEDfwd is the optimum glow voltage of the LED or the forward voltage drop spec.
I is the optimum current for the LED as specified in its datasheet.
That's all..... now your circuit is ready and would be capable of handling any type of high watt LEd in the range....