[sdiy] connectors for power distribution

[Seb Francis]

Samppa Tolvanen wrote:

>On 1/25/06, Seb Francis <seb at burnit.co.uk> wrote:
>  
>
>>Digital Ground, or maybe 5V ?
>>
>>    
>>
>
>More questions coming..
>I´m still on planning stage for my modular. The form factor of 6U
>euroracks is dictated by the budget. All recycled from the old Telco
>equipment.
>
>And despite of all warnings I´m going to build my own PSU (probably
>torroid, 317/337 + pass transistor booster - "You´re calling THAT a
>PSU? If you can´t weld with it, it ain´t PSU in my books" :P) and
>distribute it to the all other racks.
>
>Here we go: What do you people think, is it better to use local
>regulation for 5VDC digital stuff in the modules or going to concept
>of having +5VDC distributed too? (with separated digital or "dirty"
>ground, only connected in the PSU)
>
>  
>

Personally I'm very much in favour of a digital ground if you're running 
things like microcontrollers.  This is kept separate all the way back to 
the PSU and really helps isolate the noise from the audio and CV paths.  
You may find there are some things in a circuit that are not clearly 
digital or analog, but generally the things that matter will be obvious.

As for 5V: unless you have modules that are using a lot of current at 
this voltage then I would opt to have a 78L05 + a couple caps on the 
boards where you need this voltage.  In fact these components will take 
up no more board space than if you were to include an inductor and 
capacitor where external 5V power comes into the module.  The advantage 
with having it separately regulated is you can keep really dirty power 
(e.g. powering a microcontroller) local and if you have another module 
that uses 5V for something audio or CV based then it will not pick up 
the crap.

For all modules I would include some small inductors on the power rails 
(not the ground) to help isolate noise, and have electrolytic capactors 
to ground after the inductors to handle any current spikes that would be 
difficult to pull through the inductors.

Seb