Im building an DIY flood alarm for my sewage treatment plant.

Part of it uses a 555 chip as an oscillator to operate a loud 12v buzzer.

I think the current / voltage will be too much for the 555 chip so was thinking to use the output from pin 3 to switch a transistor to operate the buzzer.

However my knowledge of these things is very limited and I need to know what sort of transistor to buy as Im baffled by the myriad of transistor types.

Any helpful suggestions gratefully received. Jules

https://www.ebay.co.uk/itm/277332186427

All in one solution

Thanks

However Im not sure how that will be converted into an alarm for me.

What I want is a mains independent visual/audible alarm that is activated by an in-tank float switch (which I already have).

At the moment my alarm runs off a 9V battery and simply switches on a LED strobe light but I wanted an audible alarm that wouldnt drain the battery too quickly as the alarm may need to be able to run run for several days before anyone notices it ). Hence the idea of using the 555 timer to turn the buzzer on and off.

Ive already popped one 555 outputting to a buzzer.
So I thought the output from the 555 timer could activate the buzzer via a transistor switch . But I dont know what transistor to get for a 12V buzzer. Jules

I bit more research by me indicates I need a NPN transistor.

Something to do as winter nights draw in. Jules

Try this site it has a siren project.

https://www.build-electronic-circuits.com/555-timer/

or this Fire Alarm cct

https://www.circuits-diy.com/how-to-make-a...555-timer/ FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 85k+ miles) (MY2015)
Metro in its 12th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

Jules
On further thoughts, if you are just trying to use a low current/power source to control a high current/power source, why not use a simple relay.

As a further thought, the FL2 uses FETs to do a similar job on the lamps. FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 85k+ miles) (MY2015)
Metro in its 12th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

I built a couple of automatic feeders for our shoot and used MOSFETs to switch the spinner motor. 11 GS Bali Blue
07 GS FL2. Usually muddy. Gone
Numerous LRs since 1963

thanks for that Jules