Hello,

I’m new to all this. My goal is to create a rotating chaser circuit to light a large scale model of the Jupiter 2 spacecraft from “Lost in Space”.

The idea is to have 32 Led’s in a chaser effect with 4 channels of 8 Led’s at a time. The Led’s are laid out in a circle of with 8 groups of 4 Led’s. Based on the arrangement it would be challenging to wire them in series. I will be using a 9-volt plug- in power supply with an output of 1-amp. There will be other lights… for the interior of the ship.

My question is resistors on the positive side of the Led’s. I’m unclear if I should treat each Led as if it’s wired separately and use 1 resistor per Led or if I’m actually using a parallel arrangement. My 680 ohm resistors are based on a 10 mA led that drops 2.2 volts.

A very basic question but I’m confused. Finally any other issues or advice on my circuit would be appreciated.

Thanks.

 

First, you have multiple outputs of the 4017 wired together - that's a no-no. Leave Q5 through Q9 disconnected. All INPUTS to CMOS logic ICs must have a current path to Vdd or Vss, but unused OUTPUTS are left disconnected.

If you're operating LEDs in parallel, you need one resistor per LED.

However, since you are using a 9v supply and your LEDs have a Vf of 2.2v, you could wire them in strings.
Two strings of three, and one string of two LEDs per 8-LED group.
The 3-LED strings would need 240 Ohm resistors.
The 2-LED strings would need 460 Ohm resistors; that's not a standard value, but you can use 470 Ohms instead.

 

Hello,

If you want the leds to have equal intensity, you could use only 2 led strings, as SgtWookie suggested.

Bertus

 

Thanks all. I will change the schematic so that Q5 - Q9 are not connected. I'll experiment with the Led's in string but was I correct that each Led would need the 680 resistor?

Thanks again - this forum is a great resource.

 

Yes, 680 Ohms was correct for one LED.

Bertus,
4 LEDs in series leaves only 200mV for the resistor, which really is not enough. Current regulation would not be good over tenperature.

 

Hello,

I was meaning to use 4 ledstrings of 2 leds with the 470 Ohms resistors..

Sorry for the misunderstanding.

Bertus

 

Thanks again. Based on the - I think I'm going with 1 resistor for each Led. More work but I don't want to have to tear the model apart if something goes wrong.