Tristated output to two common Base transistor issue

[flotulopex]

As said, the first board I made was fitted with standard leds (picture in post #12).

But, following a good old swiss habit, I observe and think how to make things even better... and get into trouble.

Frankly, I thought this kind of question would have been common, maybe even boring.

A few days ago, I made a second prototype where I used my SMD NPN's and paired the leds. The visual effect is quite good (will make a video).

Now, if I have to make a third board with MOSFETs, this won't be so terrible (the iron is still hot).

And, please remember Leonardo Da VINCI: he invented so many things but built so few. I try to balance and do the opposite

Many many thanks to all.

NB: "Swiss precision" is not a legend and if you have a closer look to a chocolate bar, you'll notice that even the hazel nuts are lined-up! And yes, I'm a musician.

[sayzer]

Hey Roger,

I am getting a lot of good stuff via this post and all is free.

But, going back to your original issue, I was wondering why don't you consider using something like 74HC164 ? You can use three or four I/O pins and control cascaded 74HC164 ICs for 20 LEDs.

You can set all 20 LEDs with uS of times at once.

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[flotulopex]

As you can see the image in my post#12, the led's PCB is quite small (narrow). It is ment to be put inside an existing stop-light case ("boîtier" in french).

I haven't enough space to put either the µc nor the power regulator on the led's PCB; this is why I made a second PCB for the "power & µc section". It is located outside the stop-light (still inside the car but not inside the case).

Finally, and this is why this all is about, I wanted to reduce the amount of wires between those two PCBs.

Voilà.

Another general info: I made my second proto with 15° leds; this viewing angle is to small, 24° must be better.