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Help

Help

(OP)
I need a 5 second logic delay but I need it to work like this....
If my logic signal goes from High to Low, I need to delay the Low for 5 seconds then be able to reset when the alarm that caused my signal to go Low clears...
Basically I have several alarm inputs, when one of these inputs goes low this will energise a relay through a relay driver, but these alarm inputs can be only momentary bounces so I need to delay the relay at least 5 seconds to make sure the alarm is real. This is all done with logic gates and a UDN2596A driver....
Any ideas??

RE: Help

This is very easily done with a simple 555 timer circuit.  You can set it to trigger on either the high-to-low or low-to-high transition of an input signal.  The time that the output is "ON" is determined by an external resistor and capacitor.  National Semiconductor (www.national.com) makes the LM555 timer IC that should due the trick.

Just a few more quesitons.  Are there any unique enviornmental requirements for this circuit (Temperature, Vibration, Humidity, etc.).  Are there any space requirements?  Cost requirements?  Life expenctance requirements? etc...


Hope this helps!

RE: Help

(OP)
Melone
Thanks for your idea, but I have a question.
Let me see if I understand this....
when my logic signal goes Low into my relay driver, this enables the relay, but I want a 5 second delay before the relay driver so when my logic goes low, the relay driver basically does not see it for 5 seconds but I also need it to stay low until my alarm condition clears and the logic line goes high again and you think I can do this with a 555 timer.
So basically I can set a timer to trigger on high/low wait 5 seconds then the output of the 555 goes low and stays low until I reset the timer?
Is this correct?

RE: Help

You can use the 5 second delay to latch on (turn the output low) your output.  This can be accomplished by using a D flip-flop with edge triggering.  Let me put something together tonight and I can email the solution to you.

Hope this helps.

RE: Help

(OP)
Cool. Thank you sir...
I look foward to seeing it.

RE: Help

(OP)
Melone, just checking back to see if you have come up with a circuit......

RE: Help

There are a couple of differenct circuits that I can think of that will do the trick.  I will email you a copy of just a couple of hand drawn circuits is you send me your email.  Just send me an email and I will reply to it with the circuits attached.

Mark_Melone@yahoo.com

RE: Help

(OP)
Mark, making sure you received my e-mail.
If not, please send to Travler64@yahoo.com
Thank you.


Jeff

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