Homemade alarm problems

[plumber1969]

Thanks Ronv

Well i have had short lived success
I have just connected two parking units up to test with out the mosfet for the leds

Just connected the parking units to a 12volt battery wired up the two negatives buzzer wires together and connected each postive of the buzzer wire to a resistor then diode then nothing ,not touching anything

Under detection from only one parking unit , if i check voltage from its postive buzzer wire and negative buzzer wire i get correct voltage of 0 -11 based on detection from parking sensor great
but if i check voltage from the negative buzzer wire which is not detecting and the negative from the one that is i have a .spike of 5 - 6volts live at the negative wire? which is connected to the unit that is not detecting

So confused.com
Also if i remove one battery negative to a parking unit i get a live at the same buzzer negative of 11volts
If i switch one unit off by a switch to from the battery live to a unit i get a 3 volt
It sounds as if there will be conflict with the negatives all touching each other

So im thinking i need to wire up each buzzer wire positive and negative indvidually and then to a mosfet for the leds to come on can i use a mosfet to connect the postive buzzer wire and negative wire to together and use the other pin to give me just voltage to then open a gate on another mosfet

Or is there another electronic component that can just use negative and postive ranging from 0-11 volts and transfer that to one wire so i can then open the gate on a mosfet

Got a dammed Headache now.Thanks Tony

 

[plumber1969]

Ok got to the bottom of some of this by turning one unit off the power drain goes through the negative buzzer wire as well as the battery negative ?
so by having the negatives wired up together can blow up the other units as it dischargers about 10 volts
would a simple blocking diode prevent this and resistor

Thanks

 

[ronv]

Is the buzzer negitive tied to the battery negitive?

Do you have a link to the detector?

 

[plumber1969]

Hello Ronv

Not sure how to check if battery is tired to negative on buzzer but there is not continunity between them

Sorry no link as the information is not helpful

If i simply turn on one unit with the buzzer connected to the unit the buzzer sounds and stops ,when i turn off the unit the buzzer sounds getting quieter and stops

If i remove the buzzer and test voltage between postive and negative i get 10.81 on start up this reduces to 0.01 / 2 /3 volts and about the same when i turn off .It like a surge ?

Now when i test voltage between the negative of the buzzer wire being switch on / off and the negative of the buzzer wire from another parking unit on but not detecting i get
turn on -0.16
turn off 10 volts
turn on 3 volts

As these wires would normally go to a buzzer they seem to be used for power on and off as well as sounding when under detection


So im thinking of just putting a blocking diode on each negative to block the current with a resistor ,i have tried this and it works

have also wired the negative side of a buzzer to negative side of buzzer wire and the postive side without diode. now when testing across both negatives the voltage is blocked

When i connect this to source it all works buzzer works and when i power on / off power makes sound and stops, and sounds when detecting How i dont know

When i now test voltage negative wire going to source and the buzzer negative wire but its buzzer`s positive side i get a live voltage at source and negative at the positive side .

My only concern now is if i just use a blocking diode would i need a resistor to dissapate the voltage

Thanks Tony got there at last