The end goal of this project is to have 6-10 LEDs arranged in a circle, much like builders make for model lighthouses and such, but instead of lighting LED(s) in a sweeping pattern, I want to invert it, so the sweeping section is actually the non-illuminated LED(s). I'm trying to stick with ICs I know, so I'm using 4017s ultimately driven from a 4047 (I want the 50% duty cycle), and I prefer to stick to 5V where I can.
I started with this pretty straightforward circuit in Multisim. I'm using a function generator instead of a 4047, since Multisim lacks that part. I have no problems wiring a pulse to a 4017, so it's not something I'm concerned about. I'm using 6 LEDs at the moment, but the logic should work for more. I know there should be NPNs and such on the LEDs, but that's not applicable at the moment:
http://www.prop-forge.com/circuits/img/SpinCircuit01.jpg
From there, I wanted to have 2 LEDs lit at any one time, so I added a second 4017, and offset the outputs by one pin. Effectively, LEDs 1&6 are lit, then 1&2, 2&3, etc.
http://www.prop-forge.com/circuits/img/SpinCircuit02.jpg
The presented an issue though (at least in Multisim), as I would now have outputs combined, so I added in diodes:
http://www.prop-forge.com/circuits/img/SpinCircuit03.jpg
So now I have a circle of 6 LEDs, with 2 LEDs next to each other lit at any one time, which generates a sweeping pattern. This is the opposite of my end goal. I needed some way to invert this, so I'd have 4 LEDs lit, and 2 off to generate the pattern. I suppose I could have used another pair of 4015s with offsets, but that is too many ICs for my taste, so I decided to try PNP transistors (2n3906). This is where I started having issues with the design. I know there needs to be a 0.7V change through the transistor to trigger it, and I know the diodes will drop the voltage from the 4017, but the math was driving me bonkers (haven't done EE in a decade), so I tinkered around in Multisim and finally got something that works. The issue I have is that it doesn't make sense to me, when I look at other examples people have done with PNPs and LEDs. Here's what I currently have that works in Multisim:
http://www.prop-forge.com/circuits/img/SpinCircuit04.jpg
I'd prefer to use 5V across the board on this project, so I have VCC at 5. The 10k pulldown resistors were added due to experience with Arduino pins, and the circuit worked after I made this addition. Now, I know what might work in Multisim won't always work in real life, and vice versa, so I want to know if there's a more elegant way to do this with the same parts. Like I said, I'm using a 4047 and 2x 4017s to drive the logic, but I would like some advice on what I can do to improve the inversion of the LED lighting.
I started with this pretty straightforward circuit in Multisim. I'm using a function generator instead of a 4047, since Multisim lacks that part. I have no problems wiring a pulse to a 4017, so it's not something I'm concerned about. I'm using 6 LEDs at the moment, but the logic should work for more. I know there should be NPNs and such on the LEDs, but that's not applicable at the moment:
http://www.prop-forge.com/circuits/img/SpinCircuit01.jpg
From there, I wanted to have 2 LEDs lit at any one time, so I added a second 4017, and offset the outputs by one pin. Effectively, LEDs 1&6 are lit, then 1&2, 2&3, etc.
http://www.prop-forge.com/circuits/img/SpinCircuit02.jpg
The presented an issue though (at least in Multisim), as I would now have outputs combined, so I added in diodes:
http://www.prop-forge.com/circuits/img/SpinCircuit03.jpg
So now I have a circle of 6 LEDs, with 2 LEDs next to each other lit at any one time, which generates a sweeping pattern. This is the opposite of my end goal. I needed some way to invert this, so I'd have 4 LEDs lit, and 2 off to generate the pattern. I suppose I could have used another pair of 4015s with offsets, but that is too many ICs for my taste, so I decided to try PNP transistors (2n3906). This is where I started having issues with the design. I know there needs to be a 0.7V change through the transistor to trigger it, and I know the diodes will drop the voltage from the 4017, but the math was driving me bonkers (haven't done EE in a decade), so I tinkered around in Multisim and finally got something that works. The issue I have is that it doesn't make sense to me, when I look at other examples people have done with PNPs and LEDs. Here's what I currently have that works in Multisim:
http://www.prop-forge.com/circuits/img/SpinCircuit04.jpg
I'd prefer to use 5V across the board on this project, so I have VCC at 5. The 10k pulldown resistors were added due to experience with Arduino pins, and the circuit worked after I made this addition. Now, I know what might work in Multisim won't always work in real life, and vice versa, so I want to know if there's a more elegant way to do this with the same parts. Like I said, I'm using a 4047 and 2x 4017s to drive the logic, but I would like some advice on what I can do to improve the inversion of the LED lighting.