Hey all,

Doing a little home project and looking for some guidance. Should be basic enough for you guys!

Looking to connect a battery supply up to toggle switches which when activated will turn on LED lights and trigger a buzzer. Wondering if this circuit below will work?

 

Welcome to AAC!
Even if the speaker is merely representing a buzzer with a resistance greater than 8Ω, you risk passing too much current through the LEDs and frying them unless you are certain the buzzer cannot draw more current than the rated LED maximum current (normally ~20mA for the average LED).

 

Welcome to AAC!
Even if the speaker is merely representing a buzzer with a resistance greater than 8Ω, you risk passing too much current through the LEDs and frying them unless you are certain the buzzer cannot draw more current than the rated LED maximum current (normally ~20mA for the average LED).

Thanks for the welcome and the reply!

Apologies, the speaker resistance was just the default setting on there. These are the LED's and Buzzer that I intend to use:

LED: https://uk.rs-online.com/web/p/pilot-light-complete-units/7637915/
Buzzer: https://uk.rs-online.com/web/p/buzzers/3119107/

 

Well, the buzzer's datasheet says that it needs 8 mA to operate, but as those leds are intended for direct connection to 24v, they will have an internal resistor calculated for direct connection to 24v, and the leds case reads "current <= 20 mA". So, if it works or not, it depends a lot on what kind of circuit is inside the buzzer. At the very least, it will be a lot dimmer than normal. The buzzer could also sound softer.

You could try, however. Nothing should broke by trying in this case, as the current would be lower than normal.

If it doesn't works correctly, then you cannot connect the buzzer in series with the leds, and must find a way to power the leds and the buzzer in parallel, and at the same time avoiding all the leds turning on at the same time. You could:

• If using DPST switches is an option, use them to send power to the leds and the buzzer in a separate way.
• If you can only use SPST switches, then you could use diodes to get power from the led's anode to the buzzer. One diode per led, so that the current will flow to the buzzer when any of the leds is powered, but the current cannot flow back to the other leds.