Introduction: Extend Old School 8V AC Doorbell With Wireless 10 EUR Doorbell

In our old house a classical electric bell system is installed. That means that there's a 8V AC power transformer installed. For each appartment there's a switch at the door and if the switch is pushed, the bell is powered by the 8V AC and rings.

As we also have a garden I wanted to extend the doorbell. Adding additional wires through the flat was no option as an additional switch at the door - too complicated.

Therfore I decided to buy for 10 Euro an wireless electrical door bell which consists out of 2 components: switch/transmitter with a 3V coin cell and receiver with 2 AA batteries and the possibility to control sound and volume.

The remaining challenge was now to connect both. As I'm a rookie in electronics it took me some time to figure out how to do it and also the soldering technique might not be perfect - but it works.

If you got additional remarks/ideas please let me know.

Step 1: Open the Transmitter and Solder Wires to the Switch

Depending on the model you have it might look differrent. But what you want to achieve is to "extend" the switch to get it switched by a relay at the end. Therefore solder two wires just next to the switch. If you're careful you'll be able to remove it and to use it as normal switch again.

Step 2: Create the Circuit

What you need to achieve is to transform AC into DC in order to switch the relay. The relay will then "push" the button of the transmitter and send a signal to the receiver which will ring.

Attached you can find the layout. You will need:

- 1 relay (I took a Songle SRD-05VDC-SL-C but similar should work too)

- 5 diodes 1N4001

- 1 electrolytic capacitor 100 micro farad

- 1 current terminal (2 pin) (optional, you can also solder)

- 1 case (optional)

Step 3: Connect Transmitter to Circuit, Old Bell and Test

Now you can connect the circuit to the transmitter and to the old door bell and test it.