evening

i am not sure if the name of the topic of "switch watchdog" is correct but i am trying to get some help in a little problem i am having getting my head around.

i have a switch that requires that requires some sort of watchdog:

1) Start signal is via an input and latched from outside source.

2) if switch is already in CLOSED position then this prevents the system starting and provide an alarm saying  "switch in closed position".

3) if switch NOT OPEN then start system and after a time elaspe (10s) if switch is made then switch is "proved" and provide an ouput for this.

4) when system is running and switch becomes OPEN then system gives output to stop and gives alarm to say "switch failed when running".

5) all alarms can be reset by either the start signal being lost or by reset input.

Any help on this would be ideal, thanks

sorry my mistake that should be switch OPEN not "NOT OPEN"

3) if switch OPEN then start system and after a time elaspe (10s) if switch is made then switch is "proved" and provide an ouput for this.

hello thedodgy1,

Unfortunately, your description seems very general and rather abstract. With Pos. 2 & 3 I miss the dependency on the input of the external switch. You'll have to provide a more detailed description so that we can understand this.

greeting Ella_68

input 1 = start

input 2  = proximity switch

Output 1 = Fan

if input 1 = true and input 2 = true then output 1 = false and alarm "switch welded"

if input 1 = true and input 2 = false then output 1 = true

if time => than 6s and output 1 = true and input 1 = true and input 2 = false then output 1 = false and alarm " failed to prove"

if output 1 = true and input 2 = false then output 1 = false and alarm "failed while running"

Hope this explains it a little better.

With the description you have basically already written your program.

But what is still completely unknown: What starts the time (6s)?

thedodgy1

if input 1 = true and input 2 = false then output 1 = true

if time => than 6s and output 1 = true and input 1 = true and input 2 = false then output 1 = false and alarm " failed to prove"

doesn't that contradict itself ? The fan would only run for 6s and then generate an error. In any case, I've implemented your description. maybe it fits.

Ella_68