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  #1  
Old 04-20-2008, 01:23 AM
pauliewalnuts pauliewalnuts is offline
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Default 1 Minute Time Delay using a 555 Timer

Hi,
I need to create a delay of 1 minute using a 555 Timer. The Timer will receive an input from a relay contact (this is not a constant supply), then wait for 1 minute before giving a one shot output.
Is this an easy circuit to build? I have come across plenty of timer circuits that will give an output FOR a set time, I need the circuit to WAIT for 1 minute then give the output.
Many thanks for any help.
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Old 04-20-2008, 01:25 AM
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How long is the one shot period and what polarity must it be?
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Old 04-20-2008, 01:29 AM
pauliewalnuts pauliewalnuts is offline
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The one shot is just a positve feed to a PLC, the timer only has to give an output for approx 1 sec.
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Old 04-20-2008, 01:54 AM
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beenthere beenthere is offline
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You will need two 555's (or a 556). The first will go active for 1 minute from the relay contact, and will trigger the second when it times out.
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Old 04-20-2008, 02:05 AM
pauliewalnuts pauliewalnuts is offline
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Thanks, Im a bit of a novice when it comes to 555 timers. I have heard of a 556 though. Would you mind explaining a little more about the reason for needing two 555's - when you say the first will go active for 1 minute, then trigger the second.
Thanks a lot.
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Old 04-20-2008, 02:14 AM
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beenthere beenthere is offline
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When a device is triggered, the output state changes. So a single 555 won't do for your needs. The idea of using two of them is that the first one can trigger the second one. The first gives the 1 minute delay and the second gives the 1 second output pulse.

I'm pretty sure that an LM556 is a dual 555. At any rate, get the data sheet for both.

I'm off to bed, try to be more useful tomorrow.
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Old 04-20-2008, 02:24 AM
pauliewalnuts pauliewalnuts is offline
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So are you saying that the first will give an output FOR 1 minute, and the second wont do anything until the output from the first 555 goes low.
So the first 555 will immediatley give an output once the relay contact goes high (for 1 minute), and the second will give an output for 1 sec AFTER 1 minute has passed?
Sorry for being a bit of a thicko here but your really helping me out. Many thanks again.
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Old 04-20-2008, 12:23 PM
KMoffett KMoffett is offline
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See "Two Stage Time Delay Circuit" :

http://home.cogeco.ca/~rpaisley4/LM555.html#20

Lots of other good 555 stuff here too.

Ken
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Old 04-20-2008, 02:03 PM
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Quote:
Originally Posted by beenthere View Post
You will need two 555's (or a 556). The first will go active for 1 minute from the relay contact, and will trigger the second when it times out.
If you want you can you use one 555 and a transistor to invert its output. But why dont you use the PLC itself to make the 1 minute delay?
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Old 04-20-2008, 04:13 PM
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See the attached schematic. Times are approximate, of course - your mileage may vary. You can use two 555 ICs, or a single 556.
Attached Images
File Type: png 555delay1minpulse1sec.PNG (34.6 KB, 454 views)
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Last edited by SgtWookie; 04-20-2008 at 04:40 PM.
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