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555 (or any) timers

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jonesa4

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I need to create a timer (approx 2 minutes timeout) which will switch on a lamp and alarm if the 2 minutes elapses (no control signals will be given).
This lamp should remain on until a hard reset is performed.
I had the idea of using a 555 timer feeding into an SCR with a push switch in series with the SCR to break the current as a reset.
Not sure though how I can use the 555 as a timer since it would appear to need a trigger but I am sure it can be done.
Any clever people out there have any ideas - maybe you can tell me of any easier ways (so long as they are cheap)
 

codan

New Member
I need to create a timer (approx 2 minutes timeout) which will switch on a lamp and alarm if the 2 minutes elapses (no control signals will be given).
This lamp should remain on until a hard reset is performed.
I had the idea of using a 555 timer feeding into an SCR with a push switch in series with the SCR to break the current as a reset.
Not sure though how I can use the 555 as a timer since it would appear to need a trigger but I am sure it can be done.
Any clever people out there have any ideas - maybe you can tell me of any easier ways (so long as they are cheap)

You could save yourself some time & just purchase an Electronic Egg Timer for a few dollars & set whatever time you need.
All you would need to do is connect to the wires from the time Alarm & use these to switch a relay for the light. Just press the button to reset.

Not sure if the light is 240v Ac or not but if it is you will need a suitable relay.
 

jonesa4

New Member
What I am trying to do is find out if a program hangs up. I will send out an electronic pulse every minute to reset the timer but if the program hangs, no pulse will be sent so I need the alarm to go off automaticallt
 

codan

New Member
What I am trying to do is find out if a program hangs up. I will send out an electronic pulse every minute to reset the timer but if the program hangs, no pulse will be sent so I need the alarm to go off automaticallt

The above will do that, if you dont reset the timer the Alarm will go off automatically when the set time limit is up. Basically an Electronic Egg Timer is a Universal Timer Circuit & that's what you want.
 
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