voltage switch for bluetooth

[pwsn]

Hi all,

I'm trying to convert the buzzer from a kitchen timer into a switch for a bluetooth headset. I figure a capacitor would be able to smooth out the voltages changes in the buzzer, and an NPN would be able to act as the switch.

The problem comes in that if the switch is kept on for longer than 8 seconds, the bluetooth will enter pairing mode and won't connect. How would I be able to open the switch with voltage and close it after a time delay even when voltage is still supplied?

[michaeliv]

555 timer circuit or arduino. What power sources do you have available, what's the max allowed power consumption ?

[pwsn]

I have 3 volts from 2 AAA batteries. was hoping to fit all the components back into the kitchen timer.
it seemed like such a simple task in the beginning

[michaeliv]

It could be simpler, You can probably do it with 1-2 MOSFETs, a capacitor and 2-3 resistors, but will only be able to draw/check the schematic later.

[michaeliv]

Also, do you have shared ground / power between the timer and bluetooth device ?
If not, may also want to check what resistance the bluetooth device considers a press being made (by adjusting a potentiometer and see at what value a press begins).

[pwsn]

I do have a shared power source

[michaeliv]

Attached is a circuit that might work. I say might because it depends on how the bluetooth button actually works ( connects a positive voltage to ground, etc ) and how the piezo buzzer is driven, if it even has enough voltage to charge the capacitor, if not you want to amplify it with another transistor. Also on what resistance the bluetooth device recognizes as pressed vs not pressed.
Depending on all of those you're going to want to choose different values for the cap, resistors + different MOSFET
Connect piezo on the left, and bluetooth button on the right.

[pwsn]

i'll need to order that pchannel mosfet and give it a try. thank you!