[sdiy] get 5V from 12V - DC-DC converter or 7805?

[Florian Anwander]

Hello,

I am at designing the pcb for a simple  MIDI-sequencer based on an 
arduino nano (the basic idea is derived from the JX-3P / SH-101 
sequencer). I want to build it as a euro rack module, but want to have 
it also as standalone unit. So the pcb has the usual eurorack power 
connector and a socket for a wall wart. I have jumpers to select between 
5V from the euro rack connector, or 5V from a regulator which is fed 
either by the 12V from the eurorack connector or by 9V-12V from a wall wart.

At the moment I implemented the 5V conversion with a 7805. But I think 
this will cause a lot of "useless" current on the 12V rail of the euro 
rack. I thought about one of these DC-DC converters, but I am not sure 
how much (switching-)noise those can insert into the euro racks supply 
and ground. The module also has voltage inputs (for note length and 
velocity) and trigger/gate inputs, so electric relations with ground to 
other modules or external devices are quite likely, and I fear I 
transfer potential supply noise this way in the external signal paths.

On the other hand the 7805 circuit is quite easy to implement, the DC-DC 
converter has to be bought as module or requires buying parts I won't 
have use for anywhere else.

Does anyone have experience with those DC-DC converters?


Regards
Florian

-- 
http://www.florian-anwander.de/