Power over J2 question

[Kvetch]

Hi folks. Im very pleased with my recent midibox build, but Im looking to add another core to filter some midi signals to my footpedal. The software side of things should be very simple, but Im a little confused about powering the new core from the first one I built. I know I can connect J2 from the first to the second and dont need certain components on the second board. Should I leave them out entirely or do I need to bridge the PCB in place of them? Just not sure about the specifics. Ive read this on Ucapps to know which components to leave out:

When used as +5V input:

for supplying from J2 of another core module, or from an external stabilized Power Supply Unit (PSU). In both cases the voltage regulator (IC3) should not be connected, also the rest of the voltage stabilization circuit between J1 and J2 (X1, C5, C6) can be left out. If the core module (and all connected modules to this branch) drains more than 100 mA, it's recommended to mount C5 directly to J2 (a small cable between the outer soldering pads of the left-out 7805 will do this).

So my other question is would the new core without any LCD at all drain more than 100mA? Just to know whether to mount C5 at all.

Edit: While Im writing this I should check my software. Im trying to get the core to convert note messages to CC on a specific channel. For example I need it when note C1 is received on MIDI channel 3, the core outputs CC17 value 72. I have other note to CC values to convert, but is there any particular software programming example that would be most suited to this simple MIDI filtering/live altering? cheers!

Thanks in advance :)

Edited September 26, 2011 by Kvetch

[m00dawg]

If you are using the standard CORE, it includes a power section that is used to allow various types of power to be supplied to it and still end up with the proper voltages and things to the microcontroller and things. Basically the components allow for AC or DC to DC conversion. That comes at a cost, which is voltage drop (and heat) which means you cannot simply run 5V through these components and get 5V back.

The J2 header is placed directly after all those components so is either a stable 5V output on your main CORE board (which has the power section) or can be used as an input for other CORE boards. You just avoid populating all the power stuff. For CORE, I don't think you have to bridge anything for that to work (for the SID boards you do, last I checked).

As far as current draw, if in doubt, it probably won't hurt to mound the power cap (C5) to your periphery CORE modules. I don't think it will draw more than 100mA though if you are just using it to interface with MIDI (I could be wrong - haven't tried it :) ), though.

[Kvetch]

Thanks for the reply m00dawg. So just to confirm my already completed core contains all the power regulation components and is being fed power straight from my wall power supply. This core works fine. One more core will be added which uses no LCD or modules of any kind just a basic core. I should connect J2 (matching the 5V and Grnd pins obviously) of the working core to the new core, but on the new core I should leave out:

X1

C5

C6

And I dont need to add bridges to the second core in place of the left out components. Thats what I think ive gathered if anyone can confirm for sure :)

Cheers!

Edit: I just realised Ucapps says that X1, C5, and C6 CAN be left out, but doesnt say MUST be left out. Would the second core not work at all if these components were included anyway? Thanks

Edited September 26, 2011 by Kvetch

[m00dawg]

The second one should work just fine. I'd have to look at the schematics again but I think you can put in C5 and get the added benefit (if you wre going above 100mA for instance). It shouldn't hurt anything, anyway.

EDIT:

Correction: C5 won't really help because it's before the voltage regulator. So you can populate those components but they won't add any benefit (but won't hurt anything either) unless you make modifications.

Edited September 26, 2011 by m00dawg

[Kvetch]

Nice one! Thanks for the clarification m00dawg

:)