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!
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.
Traffic lights are classic classroom example when learning about state diagrams and/or truth tables.
I have made a fictional intersection in a pair of streets: Second avenue and Main street. Please check the attached Excel spreadsheet.
As one of the small minority of people who still insists on a proper manual gearbox I've often wished it was. Seems like a handy feature that has never been implemented in this part of the world.
The sequence seems to differ the world over.
What sequence does the original poster require?
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!
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.
My goal is to use as few components as possible!
Yes, but those use multiple ICs. Is there a single IC, besides a microcontroller, that can achieve this?
Besides a microcontroller, what’s a single simple IC that could do this? There are many 555 variants out there (like the 556), would any of those achieve this effect?
I don't see how. You'd need to add at least something to allow you to hold the second timer in reset and also prevent either LED from lighting while the first one is on. As I mentioned earlier, this is an unusual way of doing a traffic light.
That’s great, but did you try it using a 556 timer instead? Apparently it’s impossible!
...I don’t have any circuit software, so I’m drawing stuff with Adobe Illustrator....
... this circuit cannot be done with a 556...
...Frankly, most of this is over my head....
I was just hoping someone would sketch out a 556 timer circuit
Regardless of what happens, I plan on building this thing and I don’t care how long it takes me! Parts are ordered and that’s that!
I plan on attempting this circuit in 4 different ways:
1. 2x 555
2. 1x 556
...
Everyone’s help has been incredibly valuable. I will post results here!
... As I mentioned earlier, this is an unusual way of doing a traffic light.
Traffic lights are classic classroom example when learning about state diagrams and/or truth tables.
I have made a fictional intersection in a pair of streets: Second avenue and Main street. Please check the attached Excel spreadsheet.
To keep things simple, I've arbitrarily made them one way, and have not included turn signals.
The circuit has four states, which repeat endlessly and six outputs, one each for each light color on a street.
Fortunately, four states can be realized with a two bit counter, with a single IC dual flip flop like the CD4013.
Then using sums of minterms, you decode each output. For instance, the Second ave green light is simply A * B/
The fact that the yellow light has a different duration than the other lights complicates things a little, but with additional steering logic you could change your astable's time constant.
Of course, doing this with a microcontroller is trivial.
Unpopular opinion: That’s a bad idea. Giving people an exact preview of when the light will turn green is only allowing the possibly for abuse and increases the chance for a collision.
There's lots of information out there about traffic light controllers, at least the stuff used in the US. Eagle, Econolite and Crouse-Hinds were some of the big makers here. Early systems used motor driven timing wheels and solenoids, then in the early 80s microprocessor based controllers started taking over.
https://northstarhighways.wordpress.com/2016/09/10/how-traffic-signal-controllers-work-part-1-an-overview-of-controllers/
Back in the early 70s, I worked for a summer for the city’s traffic light department, in maintenance.
There were a couple of systems, that I remember:
-Relay ladder logic as you described.
-A camshaft driven by a 1RPM geared synchronous motor.
Idiots exist, ergo, why give them more ways to be idiots? Sometimes people run red lights. Why give people an incentive to gun it just when the light turns green? It’s certainly not safer to give people advance notice of a green light.
If you know exactly when the light will change, you will be encouraged to not slow down as you approach a red light and try to time your entry into the intersection precisely when the light changes. Meanwhile, a car may be trying to get through the light before it turns red. Bad combination.
I don’t have data, sorry! It just seems like a bad idea to give people advance notice when a light will turn green, which is why the US doesn’t employ that system. I can’t believe it would be safer with that feature, but I welcome any data that proves me wrong.
If you know exactly when the light will change, you will be encouraged to not slow down as you approach a red light and try to time your entry into the intersection precisely when the light changes. Meanwhile, a car may be trying to get through the light before it turns red. Bad combination.
I don’t have data, sorry! It just seems like a bad idea to give people advance notice when a light will turn green, which is why the US doesn’t employ that system. I can’t believe it would be safer with that feature, but I welcome any data that proves me wrong.
I would support red light cameras if they were about improving safety but unfortunately they end up being purely for revenue. Multiple municipalities have been caught turning down the amber light intervals and data has shown rear end accidents to increase at camera equipped intersections. In a city near me there was an attempt to put forward a citizen initiative banning red light cameras and it got shot down early in the process with an official quoting that they need the revenue.
I would support red light cameras if they were about improving safety but unfortunately they end up being purely for revenue. Multiple municipalities have been caught turning down the amber light intervals and data has shown rear end accidents to increase at camera equipped intersections. In a city near me there was an attempt to put forward a citizen initiative banning red light cameras and it got shot down early in the process with an official quoting that they need the revenue.
Wow,
the official was not fired
plus no injunction against the city?
If you know exactly when the light will change, you will be encouraged to not slow down as you approach a red light
Around my neck of the woods,
at least they have delayed the green,
as they know everyone is racing it to
get through those amber signals.
If it's just sequentially lighting the LEDs one after the other, just use a ring oscillator. Here's an example which can be built with the 74HC14.
(Attachment Link)
Not true at all. I'm literally staring at a completed circuit that is lighting up exactly the way I want (I just had to change some resistance values to introduce an instability in the cycle.)