Hold relay on for a preset time? How?

[Pete]

I am experimenting, not having touched electronics for a while.

I have a relay controlling a 240 supply, and a control input carrying 12v

What the control 12v goes live I need the 240 to switch (not a problem).
What I then need to do is to hold the relay in the on position for a
adjustable time (say 10 mins) even if the 12v input goes back to 0v. Each
time the input goes to 12v the time needs to start again.

i.e 12v switches the 240v supply, and allows the 240 to remain on for 10
mins after the 12v feed drops to 0v

What would be the easiest and simplest way to acheive this?

 

[Larry]

"Pete" <petesssdfe@hotmail.com> wrote in message news:<1JDTa.1587$B35.16162063@news-text.cableinet.net>...

I am experimenting, not having touched electronics for a while.

I have a relay controlling a 240 supply, and a control input carrying 12v

What the control 12v goes live I need the 240 to switch (not a problem).
What I then need to do is to hold the relay in the on position for a
adjustable time (say 10 mins) even if the 12v input goes back to 0v. Each
time the input goes to 12v the time needs to start again.

i.e 12v switches the 240v supply, and allows the 240 to remain on for 10
mins after the 12v feed drops to 0v

What would be the easiest and simplest way to acheive this?
If you have 120AC at site for use a 12V (DC ?) relay to give you a dry

set of contacts to control a off delay relay (120VAC most common) type
If Voltage and or contacts of OFF delay relay to low use it to drive
rated power relay.

Hope it helps

 

Go here : http://www.altronix.com/p_html/6030.htm

I have used these timers alot. They work great and may work in your
application. Although, you may have to interface a relay that can
handle your voltage. Cost is about $15.00

tetek


On Wed, 23 Jul 2003 22:10:05 GMT, "Pete" <petesssdfe@hotmail.com>
wrote:

I am experimenting, not having touched electronics for a while.

I have a relay controlling a 240 supply, and a control input carrying 12v

What the control 12v goes live I need the 240 to switch (not a problem).
What I then need to do is to hold the relay in the on position for a
adjustable time (say 10 mins) even if the 12v input goes back to 0v. Each
time the input goes to 12v the time needs to start again.

i.e 12v switches the 240v supply, and allows the 240 to remain on for 10
mins after the 12v feed drops to 0v

What would be the easiest and simplest way to acheive this?