DIY Audio Alarm System

[Mad Props]

Not sure if this is of any interest to people, but I "finished" (never really finished) a restoration on my Bayliner last year and was wrapping up some odds and ends this spring/summer, one of which was the fact that my mercruiser alarm was not working. I pulled the buzzer and tested it on my bench and it was not working. So instead of dropping 100 dollars on a replacement merc one I bought a el cheapo buzzer from amazon for like 10 bucks...

While at it, I decided to turn a simple swap out into a project. The new buzzer was super loud, so my initial thought was to put a resistor in series to quiet it down a little, but then realized thats not something you potentially don't want to hear when under way with the wind and engine noise.

So I decided to build a time delay circuit that gives you ~10 seconds until the buzzer starts... This should be enough time to turn the key to on, pump the throttle a few times and start the motor without going deaf...
I believe mercruiser made some version of this at some point, but my boat was never equipped with the timer. I also am going to put a push button on the switch panel somewhere that grounds out the tan/blue wire so I can test the alarm since ideally I will never hear it anymore.. Or I could just make a habit of every once in a while giving it 10 seconds before starting the motor.

Anywho... just thought I'd post this if anyone was interested in the idea... I decided to do it this way cuz I like doing electronics type stuff as a hobby and had all the components already.
But it would be much easier to just buy a premade time delay relay off amazon/ebay and just splice it into your circuit..

Anways... Heres the final product/schematic
(I know its not pretty lol - covered in hotglue to keep moisture out and eliminate vibration issues.)

 

[Bondo]

Ayuh,.... Pretty Cool,........

But to be honest, the 1st thing I do to new toys is to unplug the damn buzzer,....

 

[achris]

Nice. Yes in the late 80s/early 90s Merc did have a time delay... (Love Multisim)

Chris..

 

[dubs283]

Ya spent 10 bucks on a warning horn and proceed to fab a resistance device to alleviate voltage/response from the horn to make the audio level tolerable?

My best approach would be to jam a cig butt in the horn, listen to the quiet hum while Amazon delivers a few more horns of varying quality. $100 goes a ways online......

 

[Mad Props]

Ayuh,.... Pretty Cool,........

But to be honest, the 1st thing I do to new toys is to unplug the damn buzzer,....

I agree that it's annoying, but thats kinda the point right? Haha

I was also thinking of adding another pressure switch to the water side as well so it would trigger the alarm if the impeller blows up or I go through a forest of grasses and plug up the inlets...
I would think that drop in pressure would be an immediate feedback to a problem, where the high water temperature switch seems like it could be a little slow to trigger and be too late

 

[savery]

Much more elegant than the one I dreamed up. Mine has an alarm horn silence switch, but it's just momentary and pointless unless you sit there and hold it while starting one handed. I "devised" a latching relay circuit that would silence the alarm horn when the switch was depressed, but as soon as the alarm condition was cleared it would return to its normally closed state so the buzzer can sound again if the condition returns.

 

[Scott Danforth]

I run an oil pressure switch and water temp switch to the ground side of my buzzer/light and a silence switch to the positive side.

no relays, etc

 

[achris]

Much more elegant than the one I dreamed up. Mine has an alarm horn silence switch, but it's just momentary and pointless unless you sit there and hold it while starting one handed. I "devised" a latching relay circuit that would silence the alarm horn when the switch was depressed, but as soon as the alarm condition was cleared it would return to its normally closed state so the buzzer can sound again if the condition returns.
View attachment 364757

Change your grounds to +12v and you'll have a fully working circuit... The alarm switches (water temp, oil pressure and drive oil level) switch to ground, not 12v.

Chris......