# Sequential circuit with more than 10 LEDs

I need to build a sequential LED circuit that will have more than 10 LEDs in a sequence. The LEDs should blink only one at a time. I know I can do 10 LEDs with a 4017 decade counter easily, but I dont know how to go beyond 10 LEDs in a row. Say I need few tenths of LEDS, maybe 50 or 100 pcs.

I found a circuit with 2 4017s which does 16 LEDs - see here. It says the design can be expanded "indefinitely" by adding more 4017s but it is not clear to me how to do it. Also, it the "reset" circuit part necessary?

• Cascading 4017. Combine the 555 timer from your linked diagram as the clock to this electro-tech-online.com/attachments/4017-expansion-jpg.11881 which uses and gates to cascade multiple 4017s Sep 18, 2014 at 23:35
• Ok, I understand the cascading diagram. What if I want my row of LEDs to run in a loop? Sep 19, 2014 at 0:29
• The last output of the last 4017 triggers the reset of the first 4017, causing the sequence to start over. So each led lights up once, in order, before it starts over Sep 19, 2014 at 2:15
• I am trying to connect all 10 LEDs from a single 4017 to a common cathode resistor, but only the first blinks... Sep 21, 2014 at 12:00
• There is another question about cascading 4017s: electronics.stackexchange.com/questions/33652/… Sep 24, 2014 at 20:26

If they can all be on the same amount of time, I'd just use lots of shift registers. There are several types. For your application look for Serial In, Parallel Out (SIPO).

If it mattered how bright the LEDs are, and you want very bright, use 'proper' LED display drivers.

For example TI Display drivers

They come in 8-LED, 16-LED and even 24-LED devices.

A SIPO shift register can be chained together by driving them all from a common clock, and connecting Serial Out of one device to Serial In of the next device. They may also have an enable which trasfers the shifted bit pattern into the LED drivers.

Initialisation, power on, must clear all of them to zero (usually a RESET), and initially load a 1 to the first shift register.

Edit: Removed concerns about 4017, as they don't apply.

A datasheet for 4017 which shows a schematic for cascading three (and hence more) 4017 in Figure 12 page 15.

• @EMFields - I have updated my answer. The question requires one LED on, so chips which each initialise to have an 'on' for each chip seems like a nightmare. Sep 19, 2014 at 0:29
• I do not really understand your objections against 4017. In this video the cascading of 4017s seems to work: youtube.com/watch?v=2eS9V9kDxCI It is true that guy uses few more ICs though namely 4049 and 4081 (I have no idea what those are for). Unfortunately he did not attach schematics. Sep 19, 2014 at 0:37
• @Kozuch - I was wrong. I have found a schematic for cascading 4017s. I hadn't recognised the sneaky design before. Sep 19, 2014 at 1:15
• Passerby commented on my question with the cascading idea just few minutes before your original answer. I guess you just missed that comment. Sep 19, 2014 at 15:44
• @Kozuch - I guess so. I remember I was looking for a LED display driver page at TI for a while. Rather than identify a single part, I thought it was better to link to a range of parts. Sep 19, 2014 at 17:04