# Dog at the Door Alarm

Discussion in 'The Projects Forum' started by iONic, Oct 30, 2009.

1. ### iONic Thread Starter AAC Fanatic!

Nov 16, 2007
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I need to build a "Dog at the Door" monitor that will alert me when my dog approaches the door. I have a PIR sensor circuit that puts out an active high for .5 sec and will stay high as long as there is motion. What I'd like to do with this is feed it into a 555 that is on for 30 sec, the output is the input to another 555 whose time is aprox. 5 sec, then off (this is the alarm buzzer).
When the 30 sec is up I need to reset the first 555 to be triggered from any new motion. In other words I only want to hear 5 sec of sound in a given 30 sec, regardless if there is still motion.

Can two 555's or a 556 timer be setup to accomplish this or do I need another IC for latching... I think some how I need to latch the input of the first 555 low when the PIR goes high the first time, then after 30 sec. reset the 555 high so it can detect movement again.

Any circuit help would be helpful.

2. ### MikeML AAC Fanatic!

Oct 2, 2009
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Does the initial motion trigger the alarm for 5 sec, and then the alarm is locked out for the next 25 sec even if there is continuous motion?

May 26, 2009
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Nov 16, 2007
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5. ### iONic Thread Starter AAC Fanatic!

Nov 16, 2007
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Essentially, yes.

6. ### ELECTRONERD Senior Member

May 26, 2009
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Would you still consider it if you eliminated some of the unecessary "luxurious" features? Or, would you like to continue with your project?

Austin

7. ### iONic Thread Starter AAC Fanatic!

Nov 16, 2007
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I live in the North East and anything that is not weather tight and insulated is out of the question.

8. ### MikeML AAC Fanatic!

Oct 2, 2009
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Let's see if this State Transition Diagram describes what you are trying to do:

The State Machine is sitting in the IDLE state. The PIR input becomes true, causing an instant transition to the ALARM state, where a buzzer sounds. It transitions to the WAIT state after 5 seconds has elapsed, thereby terminating the buzzer. It transitions back to the IDLE state after 25 sec. If the PIR signal is still true, it instantly transitions to the ALARM state, repeating the cycle; otherwise it just sits in the IDLE state until the PIR input becomes true again.

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9. ### iONic Thread Starter AAC Fanatic!

Nov 16, 2007
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I think that is correct. Motion triggers a 30 sec loop always (the first 5 sec with audio and the next 25 sec without), resets and checks for motion. If true the cycle repeats. If false nothing (or wait).

10. ### iONic Thread Starter AAC Fanatic!

Nov 16, 2007
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How does this look.... feasible?

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11. ### KL7AJ AAC Fanatic!

Nov 4, 2008
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Unless you want the door opening for every critter or human that walks by, there has to be some sort of "dog-unique" identifier, like the collar in this project.

eric

12. ### iONic Thread Starter AAC Fanatic!

Nov 16, 2007
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It will be directed across a door on a deck towards the back of the house. The PIR doesn't have but more than a 10 foot range and pretty much nothing will be walking by. This should be a non-issue. Pluss the door will not open, but it will alert me that I do neeed to open it for my dog...

It should trigger from the +5V logic signal from the motion sensor and should not trigger again for 30 seconds, if there is motion.