Decoupling Capacitor to add delay in relay circuit
Decoupling Capacitor to add delay in relay circuit
(OP)
I have a simple relay control system on a machine. A local switch is driven by a 120VAC supply. It appears that this switch sees small transients which can cause it to trip the relay it feeds and cause the machine to trip out.
My question is: How do I size/spec a decoupling capacitor to add a short (say 2-5 second) delay in the reaction of the switch to the relay.
Full disclosure: I am a mechanical engineer and therefore somewhat less wise to circuitry and control than a brick wall.
My question is: How do I size/spec a decoupling capacitor to add a short (say 2-5 second) delay in the reaction of the switch to the relay.
Full disclosure: I am a mechanical engineer and therefore somewhat less wise to circuitry and control than a brick wall.





RE: Decoupling Capacitor to add delay in relay circuit
Can you post a circuit drawing? What type of switch? Why do you suspect transients?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Decoupling Capacitor to add delay in relay circuit
If referring to a control relay, there are versions called "On-Delay* Timers" that can be set to not change state until a user set time period has elapsed. When used in situations like what I think you are describing, they are called "De-bounce Timers" because they delay activation until a limit switch or float or other mechanical device quits bouncing around.
*Also called "Delay-on-Make", or NOTC for Normally Open, Timed to Close, several other descriptive terms.
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RE: Decoupling Capacitor to add delay in relay circuit
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Decoupling Capacitor to add delay in relay circuit
I'll try and find a circuit diagram / logic diagram (no promises, the system was built in 1984 and the documentation has grown legs). The trips are due to a level float in an oil sump, it has some jitter to it.
jraef,
That may be exactly what I'm thinking. The switch is normally closed, energized, and when it goes into a bad condition it opens and de-energizes the relay circuit. This in turn trips the machine to prevent it from having damage due to low oil level.
I'll try and find more information on this system so I can pose the question in a better format.
RE: Decoupling Capacitor to add delay in relay circuit
Bill
--------------------
"Why not the best?"
Jimmy Carter