I need help with the series of monostable configuration of 555 Timers. The idea is to light up the different LEDs with different timings triggered by the falling edge of the previous timer, with the initial monostable setup being triggered by the switch. The first LEd lights up for 3 mins , then the next for 1 sec and the next for 1 min and so on for six LEDs.
However when i'm running the simulation in multisim , all the LEDs are already initially lit up except the first one. Can you please tell me what i'm doing wrong?
Any other ideas to light up LEDs one after another with their individual timings? i'm attaching the image below ( Ignore the resistor values , they're approximate , my issue is the LEDs lighting up without the previous 555's trigger as soon as i run the program )

 

Hello,

Perhaps you will need a power on reset.
Also the leds do not have any current limiting resistors.

Also the triggeling should be different.
Have a look at the schematic from the TI datasheet:



Bertus

 

Thank you so much ! I'll read and try it out.

 

This is a natural solution for an ATTINY, no external components
except bypass cap, one chip, sImple code in Basic.....Just
a thought.

https://www.mcselec.com/index.php?option=com_content&task=view&id=314&Itemid=117

https://www.microchip.com/wwwproducts/en/ATtiny85

Regards, Dana.

 

This is a natural solution for an ATTINY, no external components

How is that possible for 6 LEDs?

 

However when i'm running the simulation in multisim , all the LEDs are already initially lit up except the first one. Can you please tell me what i'm doing wrong?

The 555 Trigger input is a level detect, not edge detect, and at power-up all the 555 inputs are low so they all trigger on.
Thus the trigger inputs need to be AC coupled so they respond to the negative signal edge, as shown in bertus's post.

 

His timing diagram shows one led on at a time, so two leds/pin,
one source drive, one sink drive, tristate both off. 3 pins. 1 pin
for switch.

Or one led / pin, switch turns on power to ATTINY to initiate sequence.

 

Or one led / pin, switch turns on power to ATTINY to initiate sequence.

So you have one ATTINY per LED?

 

1 ATTINY, 6 LEDs, 6 LED Rilims, 6 GPIO pins,
a switch as power switch for ATTINY to turn it
on and issue the sequence.

OR

1 ATTINY, 6 LEDs, 3 LED Rilims, 3 GPIO pins (2 LEDs/pin),
a switch as input to a pin to trigger the sequence.

for both a power source, and a bypass cap.

On power up GPIO pins in HiZ.

Total timing accuracy +/- 1% with user cal at test, or +/- 10% without.

 

The circuit posted by Bertus is ok, but with the outputs connected to ground via a LED and resistor I would worry about how the circuit will behave from startup, and probably drop in a RC net at each reset to insure they all start low.

The first one also needs a pullup resistor at the trigger, to avoid spurious starts. (not to mention the problems concerned by that switch also missing an AC input if the first timing cycle has to be shorter than the button push)

 

HI

Here's an option using CD14538B's.
I didn't draw the all six timers but three more could easily be added.
Each timer triggers on the falling edge of the previous timer

eT

 

Something like this, see attached.

Code in C or Bascom Basic or Arduino IDE. Program code into chip with Arduino.

https://create.arduino.cc/projecthub/arjun/programming-attiny85-with-arduino-uno-afb829

 

Something like this

There is no current limiting for the two LEDs in series to the supply.
And how can you turn off all the LEDs with that circuit?

 

Another approach with PSOC



Timing accuracy overall +/- 2%

$4 board to use -

http://www.cypress.com/documentation/development-kitsboards/psoc-4-cy8ckit-049-4xxx-prototyping-kits

 

You are right crutschow, I modified the post.

A technique to drive two leds on one pin, but parts count up -

https://www.edn.com/design/power-ma...in-drives-two-LEDs-with-low-quiescent-current

Regards, Dana.

 

I would worry about how the circuit will behave from startup, and probably drop in a RC net at each reset to insure they all start low.

Since none of the resets are used to control any outputs, one R-C network can drive all reset pins.

ak