Pondering Power distribution

MIDIbox SID
1

After having constructed the core and sid boards successfully, I got more and now have all the hardware for a SIDx4 minus LED’s and a front panel.

The thing on my mind the most is powering it.

This was the current configuration before tearing it down.

After that, I though of a way I could set the boards up to reduce space, but I abandond this idea since I would not be able to stack all the modules next to each other because of the way the big caps had to be mounted for this.

This idea could be useful for those building a 1xSID with a minimal control surface in a compact case design.  8)

I’m pondering the new power design for the SIDx4.

I have three 5v 1A regulators.

The last one was enough to run the whole setup.

(the pic didn’t include the LCD screen and 1x DIN input for menu buttons and encoder)

My question is, how many mA is that pulling?

Is there a way for me to figure this out?

What I’m trying to determine is, will a single 5v 1A regulator be able to handle the power requirements for 3 core and 3 sid boards (the slaves) or would it be better to give them their own regulator each?

On the rest,

I’ve almost completed an 8xBankStick module.

I still have yet to build the two 4xDIN and 4xDOUT.

I’ve almost completed the power and serial cables.

Still working on a panel design. the end result will be detrmined by the case I find that will suit my needs.  :wink:

2

Each sid pulls at most 120 or so mA

So… .5a for 4 sids, and .5a for core…

I’m sure it can handle it just make sure you are either using a good transformer or the SID PSU…

3

Just a thought, you could use the stacking method for your setup as you dont need to mount the big cap on the core module, so the stacks could sit side by side easily. Also another thing you can do for the SID cap is to place it else where in the case and run wires back to the pcb from it. I have a big cap sitting off board which is hot glued to the bottom of the case and it works fine.

All the best,

John

4

Cap size and # depend on how much smoothing you need…

I can imagine a guy using one large cap for 2 sid boards, you could buy a larger value, or wire a few in parallel, or use a good regulated PSU and bypass the power part of the sids

5

HL-SDK

So… .5a for 4 sids, and .5a for core…

Is that .5a for a single core or all 4?

dcer10, I laughed when I thought I should have thought of that before.

thnx

:wink:

6

hmmmm… You are right… I was under the impression that one core could do all 4 sids, I know the LCD is around 300-500mA, but each core should be 200mA tops

7

I may want to consider finding an old C64 PSU brick, but I’m up for a challenge first.  :slight_smile:

Here’s what I have to work with.

I have a walwart rated at 12v 1 Amp

My previous setup was 12v and ground going to the 5v regulator.

With the backlit LCD, DINx1, 1 Core, and 1 Sid, I threw a working chipset fan from an old motherboar on it.

The fan was tapped on the 12v before the regulator to cool it fearing it would get hot to dissipate the extra voltage.

J1 on the Sid was also connected to the 12v line.

It wasn’t too noisy, but still some noise nontheless.

The power for the Core and Sid were connected to the Vout on the regulator.

I realize now that that was most likely a pretty bad setup.

(I’ll post a scematic later to show how it was connected)

This didn’t hit me untill after I started building another power distribution-type module.

On the one that I was building (yup, a schematic later), I have five 5v regulators on it.

Then I though “How much current draw???” and stopped building it.

I figure If I attempted that with the 12v 1000mA adapter…

I really don’t want to fry anything.

My thoughts on the right PSU…

I will need it to handle hardware addons.

It will need to handle a completed MBHP_SID x4 with AOUT for four 12v full on analog (not DSP IC’s) external VCFs.

I want as little noise on this puppy as possible.  :wink:

8

Here’s the schematics.

PSUv1 for the single Core and SID with minimal control surface I built.

And PSUv2 that I’ve halted on building untill I know what kind of current draw I’m looking at.

I don’t think the 12v 1000mA adapter I’m using will be able to meet power demands when I start expanding the hardware because the external VCFs I plan on using are here. http://www.musicfromouterspace.com/analogsynth/STATEVARVCFFEB2006/STATEVARVCFFEB2006.html

For all the demands, would guessing a 2 amp load to be a “safe” range? :slight_smile:

9

Why so many regulators?

FYI, the “C64 Brick” has just one 7805 in it, with a massive heatsink, as it’s regulating the second 9v AC coming out of the transformer, the first 9v AC goes direct to the plug.

Following the experiences of others, including myself, who have reused the C64 PSU, that one 7805 should be enough for the 5v supply to four Cores, four SID modules, one backlight LCD and the required DIN and DOUT modules, plus all the LEDs.

Also, you don’t need that big a capacitor on the SID module, or even on the Core… these are big in case you supply those modules with AC and need to convert it to DC via a bridge rectifier and regulator. You can put those bits external to your stacked modules. See this: http://www.ucapps.de/mbhp/mbhp_4xsid_c64_psu_optimized.pdf  and consider the 7805’s removed from the Cores, each Core gets its 5v from a common supply, the one out of the C64 PSU. You can take that idea one step further and take out the regulators on each SID module, supplying each from a common 12v supply external to the modules.

10

Hi,

If it’s for a home-made PSU, I would be careful betting that only one 7805 is enough for a complete 4xCore + 4xSID + backlight + DIN/DOUT/LEDs.

Indeed, as said previously in the post, for 4xCore + 4xSID, you already come at a consumption of ~1A. When using LCD backlight, you easily consume hundreds of mA and the same applies for the LEDs.

Some 7805 out there are supposed to deliver 1A and some others 1.5A. If you get a 1A one, you will put it down on its knees with a quad SID. With a 1.5A one I guess it should fit most of the time.

Depending on the current needed by the backlight and on the resistances chosen with the LEDs, I would add a second 7805.

There’s also another possibility (I think I saw it in a topic here too) of using a 7805 for the voltage regulation and another transistor to deliver the current. Anyway a very good heat sink is a must…

Best regards,

Lall