Electronics > Beginners
Traffic light circuit with 556 timer?
james_s:
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.
phennessey:
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?
james_s:
Well you could use a pair of 555's as done in the original circuit. There's also the classic design using a decade counter and some diode 'or' logic. http://nickviera.com/electronics/traffic_simple/
Countless other ways of achieving the same thing, most will start with something like a 555 to generate pulses and then some sort of counting logic.
phennessey:
Yes, but those use multiple ICs. Is there a single IC, besides a microcontroller, that can achieve this?
Zero999:
--- Quote from: phennessey on December 22, 2019, 08:13:20 pm ---Yes, but those use multiple ICs. Is there a single IC, besides a microcontroller, that can achieve this?
--- End quote ---
The schematic I posted previously can do it using a single IC, such as the 74HC14. Which pin goes where should be apparent when you've read the data sheet. Obviously the power pins 7 and 14 will need to be connected to 3V to 6V, with a 100nF decoupling capacitor across them.
https://www.mouser.com/datasheet/2/308/74HC14.REV1-34947.pdf
If you must use the 555 timer, you can use them as Schmitt triggers to make the same circuit as I previously posted, but will need two or three ICs.
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