New to PLCs

Hello everyone,

I hope that this is an easy question for someone here to answer, and please forgive me if I do not have to correct terminology.

I am trying to teach myself how to program a Symax 300 class 8020 PLC, and I am having problems programming an off timer delay.

What I have in this case is a pin attached to an air cylinder, and a limit switch. When the pin is up the limit switch is open.

What I need it to do is, the pin go down and stay down for a set period of time.

I have been able to create a on delay timer, but it looks like I need a relay rung.

I really do not know if I’m on the right track, but this is what I got so far.

----------------------------------------------- TIME
S25
--------[ ]------------------------------------ CLEAR
6-1 .1 sec
=8 sec
6-14

Where 6-1 is the limit switch and 6-14 is a high pressure circuit

If anyone can help I would love the input

Maybe this can get you started.

It's kind of hard to understand what you have based on the way your post displays here, but let me see if I can help a little.

First off, if memory serves, the Symax 300 is Square D PLC and a pretty old model at that. Because of this, not too many people are using this one today, I would imagine. I know its been a bunch of years since I looked at one, but let give it a go anyway.

Second, yes it looks like you are more or less on the right track.

I believe you will find that the "Time" line is continuous, the timer times until it reaches its preset value. Furthermore, the time value is set to (and held at) "0" when the "Clear" line is continuous. Then, when the timer value reaches its setpoint, referencing the timer via a contact (-| |-) or (-|/|-) is how you can use this information.

Assuming all that is true, the trick is to either turn on the timer when you want it to start timing or to use the "Clear" line to reset it when you want to start timing. Your logic will basically have you start or reset the timer at the same time the thing you want to turn off first turns on and then look for the timer to complete timing to turn it back off.

It is my belief (and that of most of the regulars on this board) that you learn best by working it out for yourself and, since you are in the initial learning stages here, I want to leave it at this for now.

Hope this helps.

Steve