three led driver

[jcurrie]

hi
I'm a hobbiest that is trying to simmulate a mars light used on locomotives in the 50's and 60's , if it is possable to do this i need to light led one then light led two putting led one out then lighting led three putting two out then lighting two again putting three out then lighting one putting two out then going back to two again on a contunious cycle.
thanks jim

 

[(*steve*)]

So you want it to go 1-2-3-2-1-2-3...

One solution is to connect up a CD4017 so that output 1 connects to LED1, output 3 to LED3, and diodes from outputs 2 and 4 connect to LED2. Output 5 connects to reset.

Then you'll need some sort of oscillator. to drive the clock input.

The LEDs will light in the following order 1 2 3 2, and then the sequence will repeat.

You could also do the same thing with a Pic (or indeed a PicAXE) but you'd have to learn to program them.

I would probably lean toward using a picAXE just because it's relatively simple and everything would be much smaller.

 

[jcurrie]

thanks steve i thought about that but never thought about using blocking diodes on the outputs, have a circuit using a 4015 it should work on the 4017 , use output of the 4017 to drive transistors on it as they drive 5mm led. will the 4017 drive 3mm leds without them or should i use them as a safety?
jim

 

[jcurrie]

Steve thanks again it works well have to tweek with the values to get the exact sweep, afraid i don't know a thing about Pic, any suggestions where to look to find info?
jim

 

[(*steve*)]

How do you want to adjust the timing? There may be some tricks that can be employed.

If you want to start with pic programming, google for picaxe. It's a simple introduction and also relatively cheap.

 

[jcurrie]

Steve i just used a trim pot on a 555 oss to adjust the sweep .
jim

 

[(*steve*)]

OK, I thought that you may have wanted to have different ON times for each LED or something.