Hi,

I need to detect if a buzzer's negative wire is switched to ground (low side switch) and have to use a PDM IX3212 for this.

I I connected a digital input like shown in the simplified wiring diagram attached.
In principle this works, but caused by the internal pull down resistor of the PDM's digital input, the buzzer gets enough ground to beep continuously in a quiet but very annoying way. There is a voltage of about 2V at the input.

Due to several reasons I have no possibility to change the layout of the wiring, so I have to detect the switch to ground.

Is there a workaround or any suggestion for this issue?

Regards
Toni

Hello toni27,

There are a couple of suggestions.

1.Try putting a reverse blocking diode in line with the Digital input. This would block any current flow from the buzzer to the internal pulldown resister and drop the Digital input voltage to around .7V when the switch was closed.
2. Change the switch to a double pole switch, one for the buzzer, and one for the input. It seems as though this may cause other problems. One of the persons who suggested this wasn't specific about the problems though.

Hoping you can get this worked out, there is nothing more annoying than a constant buzzer. I associate it with my alarm clock...

Hi Sara,

Thank you for the answer.

I hoped there was a way to switch the puldowns by software.

I used a diode like you suggested and it worked.

Best regards
Toni