In addition to commercially produced sophisticated switches, there are also instructions for the construction of simple R/C switches to be found on the Internet. Everyone who has some basic understandings of electronics can easily make simple switch. I found three basic types of circuits. With the logic circuit 4013 HERE, with logic circuit 4001 HERE and with the operational amplifer LM 339 HERE.Because I didn’t have any of those IC in drawer, I tried to use one operational amplifier I found there. It was very old MAA 741, which I had since my school years, when I experimented with Hi-Fi.
The circuit is simple, I added a power transistor KD 139 and resistance as power switch. It worked on the first attempt. This solution has bonus advantage. If you connect it to a potentiometer controlled channel, the switch operates as a dimmer, so diodes light up and fade slowly.