I'm currently working on a arduino drum sequencer. The arduino sends midi notes to a drum expander which plays the sounds. Now I want to put both the arduino and the drum expander in a case and only connect one cable for powering both.
The arduino has 7-12v dc, while the drum expander uses 12v ac. As I'm not so familiar with power circuits, how can I do that? It should include a power on/off switch.
It seems weird that it would use 12V AC - double check that.
If so, what you need is a "bridge rectifier". You can make one out of 4 diodes or buy a pre-built one.
As noted in the "Output smoothing" section on that page, you'll need to connect some capacitors across the output to smooth out the voltage. I'd use a medium sized ceramic and an electrolytic together (in parallel).