Electronics > Beginners
Traffic light circuit with 556 timer?
phennessey:
Disclaimer: this is my first electronics project ever. I understand basic electronic components and how they work, but I've never built anything in my life. I thought this project was a good starting point.
I want to build the following "traffic light" circuit that uses two 555 timers to light up three LEDs in sequence:
But...I want to use a dual 556 timer instead of two 555 timers. I attempted to re-draw this circuit with the correct pinouts and removed the extra in/out lines. I don't think I did it right...can anyone help me redraw this so that it would work with a single 556 IC?
Some info on the pinouts for the 555 and 556:
https://dlb.sa.edu.au/rehsmoodle/file.php/466/kpsec.freeuk.com/555timer.htm
Also, would it be a bad idea to build this thing on a mini 170-pin breadboard with no power rails? Is there enough room on one of those to build this?
Thanks for any help you can provide!
Wimberleytech:
--- Quote from: phennessey on December 20, 2019, 08:52:52 pm ---Disclaimer: this is my first electronics project ever. I understand basic electronic components and how they work, but I've never built anything in my life. I thought this project was a good starting point.
I want to build the following "traffic light" circuit that uses two 555 timers to light up three LEDs in sequence:
(Attachment Link)
But...I want to use a dual 556 timer instead of two 555 timers. I attempted to re-draw this circuit with the correct pinouts and removed the extra in/out lines. I don't think I did it right...can anyone help me redraw this so that it would work with a single 556 IC?
Some info on the pinouts for the 555 and 556:
https://dlb.sa.edu.au/rehsmoodle/file.php/466/kpsec.freeuk.com/555timer.htm
Also, would it be a bad idea to build this thing on a mini 170-pin breadboard with no power rails? Is there enough room on one of those to build this?
Thanks for any help you can provide!
--- End quote ---
It would be instructive for you to try to figure this out on your own. It is easy to map the functions of the pins to their respective pins.
You need to put a bypass capacitor across the supply pins (not shown in your schematic). Post your result and I or someone else will check your work.
There may be enough room to build it but you need to try to figure that out. Download a copy of Fritzing and build it there first. You can optimize placement and know ahead of time if there is enough room.
james_s:
The 556 has exactly the same pins as a pair of 555s except there is only one set of power and ground pins. What aspect is confusing you? Draw it up to the best of your ability and share that drawing and we can help you figure out anywhere you went wrong.
schmitt trigger:
I can see where his confusion is.
The left 555 powers up via its output (pin 3) the right 555's Vcc input (pin 8 ).
This circuit cannot be implemented with a 556, which share a common Vcc input.
But even then, the circuit's operation is suspect. How does the circuit cycle back to the red light once that the green times out? There is no signal feedback from right to left.
phennessey:
Thank you! I thought I was taking crazy pills.
Is there a way to wire three LEDs to a single 556 that would produce the same effect?
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