I have tried a number of remote door chimes available in Australian hardware stores and shopping centres.
The Kambrook and Arlec brand receiver section of the chime use two AA cells.
The receiver and chime are an all in one chip. There is no available technical information on the net for the chip. I managed to trace the circuit board and find the output driver transistor. The speaker positive is connected to battery positive. The speaker negative is connected to a surface mount transistor collector, the emitter to ground and the output of the chime chip drives the transistor base.
Disconnecting the speaker and connecting the output to the camera USB will not work. There is no positive voltage drive. Leaving the speaker in circuit produces about one volt output at the transistor collector connection. Too low to drive the camera USB.
I have observed the chime signal on a oscilloscope. Regardless of the chime note, the chime duration is close to five seconds.
Altronics and Jaycar are now the only electronics suppliers in Australia. Even they only have a limited electronics range.
Jaycar have a Burp machine CAT. NO. GH1081 listed on their web site for $5.00. I have not seen one except from the web picture. Judging by the description it seems the operation is the same as a wireless doorbell chime.
For the price of the unit it is worthwhile gutting one in the name of experimentation.
The following is a general guide to modifying a remote door bell chime.
Open the unit and place a digital voltmeter across the speaker terminals.
Press the remote.
If the voltage is around 1.5 volts the transistor may drive a 4N28 opto coupler Jaycar CAT. NO. ZD1928.
If the voltage is below 1.5 volts look carefully on the printed circuit board.
You will find a miniature transistor soldered flat on the printed circuit board.
One side is connected to ground. A large thick trace which may have many connections and wires connected.
You will find one trace that seems to have nothing connected to it.
Look carefully; that track will join onto a black blob; that is the onboard chime chip. On older chimes it may be a 16 pin soldered IC.
That track will be the chime output.
Place a meter probe on that track and ground.
Press the remote.
The voltage may go as high as 2 volts.
If that is the case, use that point to drive an opto coupler.
I recommend using a 500 ohm series resistor.
The output of the opto coupler can be used as a transistor switch using an external 5 volt supply to drive the camera USB.
