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General : a simple problem  
     
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 Message 1 of 10 in Discussion 
From: MSN Nickname-Whostolemymonkey-  (Original Message)Sent: 3/3/2007 10:20 AM
I have a project that I'm working on and it requires a dpdt switch input to trigger a relay, however one of these switches needs to lag behind the other switch, eg sw1a is a normal on off switch and sw1b needs a delayed switch off of about 2 or 3 seconds. Severe brain block has got me on this one, any simple circuits would be gratefully recieved.
 
Thanks 


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The number of members that recommended this message. 0 recommendations  Message 2 of 10 in Discussion 
Sent: 3/3/2007 3:38 PM
This message has been deleted due to termination of membership.

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 Message 3 of 10 in Discussion 
From: MSN Nickname-Whostolemymonkey-Sent: 3/3/2007 5:57 PM
Just what I was after, knocked the circuit up on a breadboard this afternoon.
Now all I need to do is make six of them!

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 Message 4 of 10 in Discussion 
From: MSN Nickname-Whostolemymonkey-Sent: 3/4/2007 12:04 PM
Another point to note with the diagram is that the circuit is not capable of driving relays directly, as shown, a relay will make the circuit 'lock-up'. To cure this a 1k resistor coming off of pin 3 is used to feed the base of an NPN transistor which in turn switches a relay.
I'll post an amended diagram on my site in the near future.
Thanks again for the diagram. 

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The number of members that recommended this message. 0 recommendations  Message 5 of 10 in Discussion 
Sent: 3/4/2007 5:47 PM
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 Message 6 of 10 in Discussion 
From: MSN NicknameUseableTvengineerSent: 5/7/2007 11:15 AM
dont forget to fit a diode across the relay coil to protect your npn switching transistor(or pnp......)
regards mike
 

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 Message 7 of 10 in Discussion 
From: MSN Nickname-Whostolemymonkey-Sent: 5/8/2007 9:51 PM
good point, although the relay modules I use already have the diode built in, I also used an optoisolator but this will also need a diode (unless its an opto-triac)
I'll have to ammend that diagram soon and post it here, I built the circuit and modified it to suit, works well.

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 Message 8 of 10 in Discussion 
From: MSN Nickname-Whostolemymonkey-Sent: 5/11/2007 8:08 PM
Hi Ken, any chance of posting the schematic for this again? I seem to have lost it
Thanks

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The number of members that recommended this message. 0 recommendations  Message 9 of 10 in Discussion 
Sent: 5/11/2007 8:50 PM
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 Message 10 of 10 in Discussion 
From: MSN Nickname-Whostolemymonkey-Sent: 7/6/2007 7:51 PM
Finally uploaded the amended timer plus diagram, it's in the projects folder 

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