Door bell

Hey guys, I am building my own small home automation system and the first step is to build a sensor which detects the door bell and sends a signal over 433MHz.
The trafo of the bell provides 8V AC (= Standard for Europe?!). I want to use this to power an Attiny85 and a transmitter for a short time to send the message. The “analog” bell, which plays a sound will still be connected too.

This is my schematic until now. Are there any errors? Or should this works like that?

If the person ringing the bell keeps the button pressed long enough for your circuit to send it’s code package 3-4 times, so you are sure it’s received, i see no reason for it not to work.

I would place a 100nF cap on the input side of the vreg too.
Apart for that, your circuit looks sound.

// Per.

= parallel to the 470uF capacitor?

I guess I have to try it. Shouldn't very long to send the messages though. Could I use a bigger cap if I need more time?

LastSamurai:
= parallel to the 470uF capacitor?

Yes. The small 100nF caps prevent oscillations, the big cap does not prevent this.

I never build anything without 100nF on both sides of vregs.

// Per.