Hi,
I am currently trying to design a circuit which will hopefully in effect work the same as an automotive 'lights left on' warning.
At present I'm using a relay with it's NC poles connected through supply power to a buzzer which sounds all the time. The relay is closed when the switched power is turned on, this removes supply power and hence silences the buzzer.
This seems to be a very crude way of doing things, although in my application it actually does work perfectly and doesn't draw current all the time as you might expect because the supply is not always on.
What I want to do is use transistors to switch the buzzer instead of a clunky relay.
I have included a schematic of my transistor solution which doesn't work... can anyone suggest what I have done wrong, or suggest a better way of utilising a transistor to do what I want?
Thanks,
Mark.
I am currently trying to design a circuit which will hopefully in effect work the same as an automotive 'lights left on' warning.
At present I'm using a relay with it's NC poles connected through supply power to a buzzer which sounds all the time. The relay is closed when the switched power is turned on, this removes supply power and hence silences the buzzer.
This seems to be a very crude way of doing things, although in my application it actually does work perfectly and doesn't draw current all the time as you might expect because the supply is not always on.
What I want to do is use transistors to switch the buzzer instead of a clunky relay.
I have included a schematic of my transistor solution which doesn't work... can anyone suggest what I have done wrong, or suggest a better way of utilising a transistor to do what I want?
Thanks,
Mark.