Two power supplies

[adamwg]

I am currently designing my next midibox and intend to build a sound card into it.

As the soundcard is firewire and my laptop does not supply power via firewire, i need two power supplies on the midibox. one to the core and one to the sound card.

How do i supply both of these with power with one supply? they both require different voltages and different currents. What size supply would i need (is it as simple as added the two together and buying a PSU larger enough)? How do i control the current?

The soundcard is 12V 1A

The core would be about 9V 500mA

[HL-SDK]

Make sure the soundcard doesn't also need a -12V, because for some electrical components, they need a +v, a -V and a ground.

In that case, get a 30 volt center tapped power supply rated 1.5 amps or above and look for dual power supply schematics on the internet...

If it's just +12 and +5 as you say, get a 1.5 or 2 amp transformer that gives you 14 to 16 volts, and put 2 voltage regulators on there (in parallel, not series) The 12vout goes to soundcard, and the 5vout goes to the core.

When you say build a sound card into it... are you just talking about the opl3 module? Or is this some new idea we should watch out for? ;)

[adamwg]

I have an firewire audiophile soundcard that i am going to take out of the casing and put inside my new box. I want to reduce the amount of equipment and cables i carry around with me. This way i would only have a laptop, 1 midibox, 2 power leads, 1 firewire cable and 1 phono cable.

[HL-SDK]

Get one transformer rated at LEAST one amp at 14-18 volts.

Then you can use a bridge rectifier, and ground the negative, put the positive into at least 2,200 microfarads of capacitance, then into both a +12 volt regulator, and a +5 volt regulator. That will give you +12 and +5!

:-D

[adamwg]

Thank you

I just realised that regulators regulate the current as well as power.

Now i can finish designing and start building  :-)