Edge trigger via loss of Vs on 555 help - Electronic Circuits Projects Diagrams Free

greg123 · 23rd March 2008, 02:21 PM

Thanks to Hero for getting me this far!

I want to use the attached for a timer circuit, so far got most of the componants and hurdles as well as the rest of the (exterior to the timer) circuit sorted.

However....

I need to trigger (I think this is an edge trigger?) via loss of Vs (12v). Normally, the 12v will supplied. I want the timer to produce it's output once only when the 12v is cut. Note cut, it isn't switched to 0v, it's simply a loss of a Vs voltage to the trigger. Currently I think this circuit is set up to trigger via a 0v feed when I need it to trigger by loss of 12v (output on break).

Can anyone suggest a modification or direct me to a good web page on designing edge triggering?

Thanks, Greg.

Hero999 · 23rd March 2008, 03:00 PM

This will work.

P.S.

In furure, please restrict the discussion of a circuit to just one thread; multiple threads can get confusing.

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23rd March 2008, 02:21 PM	#1
greg123	Edge trigger via loss of Vs on 555 help Thanks to Hero for getting me this far! I want to use the attached for a timer circuit, so far got most of the componants and hurdles as well as the rest of the (exterior to the timer) circuit sorted. However.... I need to trigger (I think this is an edge trigger?) via loss of Vs (12v). Normally, the 12v will supplied. I want the timer to produce it's output once only when the 12v is cut. Note cut, it isn't switched to 0v, it's simply a loss of a Vs voltage to the trigger. Currently I think this circuit is set up to trigger via a 0v feed when I need it to trigger by loss of 12v (output on break). Can anyone suggest a modification or direct me to a good web page on designing edge triggering? Thanks, Greg. Attached Thumbnails __________________ New to making electronic circuits but with a sound electrical/faultfinding and basic componant knowledge. Looking forward to learning!

23rd March 2008, 03:00 PM	#2
Hero999	This will work. P.S. In furure, please restrict the discussion of a circuit to just one thread; multiple threads can get confusing. Attached Thumbnails __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.