stoplight without timers

Hey All,

My 17 year old son has picked up an interest in plc's,
and I've been giving him little projects to work out.

I got to thinking about the tried and true stoplight project, but have to say I've never done it myself (I never went to school for controls except the school of hard knocks), but I remember seeing a post a while back by someone (lancie1 maybe?) that used an incrementing counter and compare statements instead of timers.

I like that approach, and was looking for an example to share with my son.

anyone remember seeing this or have a copy to share?

Regards
JohnR

I can see using incremental counters but I can’t see how you could do it without at least one timer. What would you use to count up with?

you could use the clock signal for counting.

I immediately thought about VHDL and found this example:
http://www.lbebooks.com/downloads/exportal/VHDL_BASYS_Example62-TrafficLights.pdf

I found it..... and it was from lancie1.....

but, my bad, it is around one timer and Limit test against the timer ACC value.

I was thinking it was an incrementing integer (triggered by a 1 sec pulse, and reset at the end of the cycle) and the light timing was accomplished by limit test or compare statements against the integer's value.

kinda the same concept, just using an incrementing integer instead of a timers ACC value.

JohnR