Hi All
I need some help with certain aspects of my simple project, I have successfully achieved my goal using a micro however, this particular circuit needs to work on minimal component count and more importantly cost. So has to be done with a transformerless resistive PSU, ideally 1 7555/555 timer and as few as possible supporting components.
Project Description: Door Sensor/Timer/Alarm
The aim is to monitor status of a door [open | closed]
On door open:
- switches 220vac to strip lighting
- starts adjustable timer 1 - 20 minutes
IF on timer expiry
- - door open - 12 vdc piezo sounds till door closed
- - door closed - reset timer, await door open
On door close:
- 220vac to strip lighting off
- turn off piezo [if active]
Door sensor | circuit Input
NO reed switch
I have used both 555 | 7555 to create adjustable timer circuit no problem, however I have a few problems I cant work out how to accomplish.
1. The output goes high on timer start and low on timer end, cant work out how to apply this to a relay | transistor to only switch piezo on AFTER timer end.?
2. How to trigger the timer to start, and then reset timer if door closes before timer end, using only one input (door reed)?
3. How to trigger timer as well as switch vac to lights using only one input (door reed)?
The schematic is VERY incomplete please read it as so.
Any pointers or ideas, schematics etc would very much be appreciated.
Regards
Jeff
I need some help with certain aspects of my simple project, I have successfully achieved my goal using a micro however, this particular circuit needs to work on minimal component count and more importantly cost. So has to be done with a transformerless resistive PSU, ideally 1 7555/555 timer and as few as possible supporting components.
Project Description: Door Sensor/Timer/Alarm
The aim is to monitor status of a door [open | closed]
On door open:
- switches 220vac to strip lighting
- starts adjustable timer 1 - 20 minutes
IF on timer expiry
- - door open - 12 vdc piezo sounds till door closed
- - door closed - reset timer, await door open
On door close:
- 220vac to strip lighting off
- turn off piezo [if active]
Door sensor | circuit Input
NO reed switch
I have used both 555 | 7555 to create adjustable timer circuit no problem, however I have a few problems I cant work out how to accomplish.
1. The output goes high on timer start and low on timer end, cant work out how to apply this to a relay | transistor to only switch piezo on AFTER timer end.?
2. How to trigger the timer to start, and then reset timer if door closes before timer end, using only one input (door reed)?
3. How to trigger timer as well as switch vac to lights using only one input (door reed)?
The schematic is VERY incomplete please read it as so.
Any pointers or ideas, schematics etc would very much be appreciated.
Regards
Jeff
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