This is my project to upgrade an A/V alarm at my workplace. My knowledge of electronics is still full of holes so your input is much appreciated.
The design presently in use is simply a mutable piezo alarm. The new design will incorporate some features which have often been talked about as desirable. Below are the schematics and illustrations. I will update this first post as I progress and will add photos once i start building.
Explanation of intended operation:
The unit is essentially a video black/ audio silent warning. There are two independent alarms which are each triggered by a DB9 pin 1 going high. Two ring illuminated push on/ push off's serve as mute buttons for each alarm. When a port triggers its alarm, the ring will flash. Upon muting, the ring goes solid red and a duration selectable interval timer generates a chirp every X seconds as a reminder that the alarm is still muted. A volume control provides a small amount of comfort adjustment if the buzzer is too loud. A panel brightness selector is useful for the night shift, for which the house lights are down and a full brightness panel would be irritating.
RENDERED ILLUSTRATION OF THE 1RU PANEL MOUNT:
THE 556 BASED INTERVAL TIMER (a reminder chirp when the alarm is left muted):
Much credit to Bill_Marsden for the design.
THE 555 OSCILLATOR CIRCUITS (Providing a selectable tone to differentiate between other alarms in the same room):
HELP CURRENTLY NEEDED ON:
* To conserve components and PCB space, is there a way to incorporate both 555 tone generators into a single cct using only one 555 chip?
* Even if I have to order overseas, I am looking for a black metal push on/ push off red ring illuminated button with a life of around 5000 to 20,000 cycles.
The design presently in use is simply a mutable piezo alarm. The new design will incorporate some features which have often been talked about as desirable. Below are the schematics and illustrations. I will update this first post as I progress and will add photos once i start building.
Explanation of intended operation:
The unit is essentially a video black/ audio silent warning. There are two independent alarms which are each triggered by a DB9 pin 1 going high. Two ring illuminated push on/ push off's serve as mute buttons for each alarm. When a port triggers its alarm, the ring will flash. Upon muting, the ring goes solid red and a duration selectable interval timer generates a chirp every X seconds as a reminder that the alarm is still muted. A volume control provides a small amount of comfort adjustment if the buzzer is too loud. A panel brightness selector is useful for the night shift, for which the house lights are down and a full brightness panel would be irritating.
RENDERED ILLUSTRATION OF THE 1RU PANEL MOUNT:
THE 556 BASED INTERVAL TIMER (a reminder chirp when the alarm is left muted):
Much credit to Bill_Marsden for the design.
THE 555 OSCILLATOR CIRCUITS (Providing a selectable tone to differentiate between other alarms in the same room):
HELP CURRENTLY NEEDED ON:
* To conserve components and PCB space, is there a way to incorporate both 555 tone generators into a single cct using only one 555 chip?
* Even if I have to order overseas, I am looking for a black metal push on/ push off red ring illuminated button with a life of around 5000 to 20,000 cycles.
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