i'm new here and also in the electronics world so pls be patient with my ignorance.

I's now months that i'm fascinated by the 555 timer. The stuff you can do with such a tiny thing is impressing.

As you can immagine i already tested most of the http://www.555-timer-circuits.com/ circuits, and also from other sites. And again ... wow!

Anyway, you know, reality is cruel.You never find what you really need.

This maybe simple for you, but for me it's a nightmare.

What i'm trying to do:

A Monostable 555 timer circuit

What should it do:

  1. Triggered by a switch, sensor (PIR) fade in 2-3s
  2. stay high for 1-3min *
  3. fade out for 2-3sec

A simple light timer for the stairs, right??? NO

What it does:

  1. Triggered by a switch, delay for 1-2sec
  2. It fades in for 2-3 sec
  3. It stays high

This is where i'm stuck atm.

But thats not all, i would like to attach mosfets or npn transistors delayed by another 100-300ms those driving a led strip of 3 leds and triggering the next one. Each strip is a stair (or step???).

I made this circuit knowing nothing and don't looking to much about if its correct because of the fact that i could use maybe npn transistors,pnp, or mosfets for this setup. using npn transistors would be cheaper but i would need to take the current from somewhere else to trigger the next one as i lose 0.7v at every gate.


simulate this circuit – Schematic created using CircuitLab

A. So is there something that would delay each step at about 200-300ms or less?

from what i read about electronics i could use capacitors. but the capacitor needs to be small as it has to fit in a tiny place over the stair so 1cm * 2cm * 5cm max I guess it needs to be a big capacitor to delay 200ms or even 100ms?? are there other components that i'm not aware of that could create a delay?

each step could have his own 555? but thats $$ and probably the worst approach?

B. naturally i also need to solve the main problem, fading out the output of the 555 after 1min or so.(monostable) it's useless if i post my circuit for the fading led as there are hundreds with a simple google search and i really don't understand them all.I use a 220uf,20k and 100k i think, a npn 2N3904 to create the fading effect. but its not working correctly.

Everything could be done easely with microcontrollers, but i really like to understand more about ic's and electronic in general.

Notes: The whole question is based on the naive idea of a fade in effect. i didn't event thinked about the fade out effect result in the array. It probably would disastrous. So my first guess is to put one 555 at the base of the stair and one on top. Both ends have triggers, and both circuits flow in a different direction once activated. But that is another sotry.

  • \$\begingroup\$ Hey, since you're fascinated by a 555 you would love microcontrollers. Using a uc is your best option: less space, power, money, headaches... Plus you get to learn something new, how does it sound? +1 for a nice written question though. \$\endgroup\$ May 17, 2015 at 10:03
  • \$\begingroup\$ i have some arduino's and raspberry pi's, and thank you for the +1, i love the arduino and raspberry... but things like the 555 are very cool. and if you plan to attach more things on a microcontroller understanding other ic's is a good starting point \$\endgroup\$
    – cocco
    May 17, 2015 at 10:04
  • \$\begingroup\$ So you are good to go! Buy/build a tiny board with an AVR microcontroller (arduino is AVR), program it, profit. \$\endgroup\$ May 17, 2015 at 10:05
  • \$\begingroup\$ I plan to trigger the 555 with an arduino until i learn how to precisely configure a sensor only with cheap components. but thats all, i know that it is not that hard to create an animation with the arduino using some flip flop ic's or i2c expanders or whatever to drive all those leads, but the point is i don't know the basics. If i want to continue using the gpio's i need to know some basics.I can't afford an arduino for each led i wanna light up. \$\endgroup\$
    – cocco
    May 17, 2015 at 10:25
  • 1
    \$\begingroup\$ Bravo for diving into the world of the 555 timer, it is indeed amazing what can be done with them. You might want to check out the entries in the '555 Design Contest' that MAKE magazine did a few years ago, the main website appears to have expired (snaffled by an online casino :-( ), but MAKE still have links to the contest entries: makezine.com/2011/04/21/555-contest-winners-announced I fully support your desire to get competent this way, without relying on the crutch of a microcontroller to do all the thinking that can be done in circuitry. \$\endgroup\$
    – Techydude
    May 17, 2015 at 11:58

1 Answer 1


Try connecting a slow monostable 555 oscillator to a simple, shift register frequency divider. This way you can shift the pulses in and they will stay on until the shift register is cleared.

Learn more about shift registers here:

Shift Registers as frequency dividers: (Not nearly as hard as it looks BTW) http://www.allaboutcircuits.com/vol_4/chpt_12/6.html

Using shift registers would eliminate the need for multiple 555 timers in your circuit and could greatly simplify the design because there is a constant time interval between lights lighting up.

I hope this solves your challenge!


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