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I've build the 555 timer and got my resistors and LEDs ready.

What I don't know or understand is how to shift a pattern using the serial in parallel out shift register (SN74LS164N).

I want to shift 10001100 using the shift register to shift LEDs (8 outputs). How can I do that? How can I make the connections or what are the connections? Or is there any other way without using this type of shift register?

Components that I've used: 555 timer capacitor resistors LEDS SIPO shift register SN74LS164N

is there anything else i need to add to the diagram? that will make the LEDs shift in the pattern

  • \$\begingroup\$ uhhh.. does this really need to be based on the 555? it would make way, way more sense to simply throw out the 555 and your shift register and replace them with a microcontroller. \$\endgroup\$ Commented Apr 18, 2020 at 11:27
  • \$\begingroup\$ sadly yes i cant throw the 555 ): \$\endgroup\$
    – Lilly A
    Commented Apr 18, 2020 at 11:29
  • \$\begingroup\$ then that means this is some kind of school assignment with specific restrictions on what components you can use, right? Then, please add these restrictions to your question (by editing it), so that we'll not give you an answer that you can't implement. \$\endgroup\$ Commented Apr 18, 2020 at 11:30
  • \$\begingroup\$ @LillyA the real problem is that this is a serial-in register. Where does your serial stream of bits come from? That needs to be synchrnous to the clock you're generating with your 555 – which makes no sense, typically. So, really, you're missing the hard part: it's not the "connections" between your shift register and your LEDs, but where that pattern comes from, and I'm 90% certain that if you have a source for that pattern, it brings its own clock and the 555 doesn't help at all. \$\endgroup\$ Commented Apr 18, 2020 at 11:34
  • \$\begingroup\$ thank you so much for editing on my behalf, i'm new to this. this is the thing! idk! that's why i'm asking for help as my instructor won't help me and i have to build it in circuit maker \$\endgroup\$
    – Lilly A
    Commented Apr 18, 2020 at 11:35

1 Answer 1


You will need to use something else to "load" the pattern into the shift register, and then once loaded, will need to change over to connect the output of the shift register to its input to keep it cycling,

As its homework, I can only guide, but not give a solid answer,

to make loading easy, lets start with an OR gate to the input of this shift register (output of the shift register on 1 leg, loading via the other)

next up is loading the correct high or low for each bit on the shift register, using say a Parrellel in serial out shift register, with its serial input tied to ground, and each bit in it set correctly, this will also mean once loaded the output will be stuck at 0, and will not effect the pattern,

Lastly have an input you control to "clear" this shift register, and "load" the other one at the same time, this way it starts reliably each and every time.

  • \$\begingroup\$ i can't using PISO, i can use SIPO and do i load it to the serial input? and then for the parallel output, i just connect it to LEDs and resistors? (i don't have the clear option, i have the reset) \$\endgroup\$
    – Lilly A
    Commented Apr 18, 2020 at 12:40
  • \$\begingroup\$ What types of shift registers do you have in circuit maker then, You may need to look at the part numbers they provide, I would expect something like a 74??165 to be in the part library. Clear is the same as reset. \$\endgroup\$
    – Reroute
    Commented Apr 18, 2020 at 12:57
  • \$\begingroup\$ i used the SIPO shift register and made it work with the pattern i wanted to! i used SN74LS164N shift register, all is left is to make it shift to infinite which idk how to \$\endgroup\$
    – Lilly A
    Commented Apr 18, 2020 at 14:05

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