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Power Supply - 3 Dizzies ???
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author Power Supply - 3 Dizzies ???
satindas
Hi, the first stage of my build is complete It's peanut butter jelly time! SlayerBadger! w00t .....

3 x VCO
VCO CONTROL
VCLFO
SVF
JOURNEYMAN
3 x ADSR
MULTIMIX
QUAD VCA
RING MOD
NOISE
OVERDRIVE
SAMPLE & HOLD
DEEP EQUINOX
(pics soon)

.... and with two dizzies I have just 7 power slots left, 4 of which are spoken for - Klee, Midi to CV, quantizer and VC Delay. That leaves just 3 slots and with space for 10 more single units in my case I'm wondering if/how I can add a third dizzy. I've used the PA30 with 0R47 resistors on the PSU board and should therefore be ok up to about 1.3A. I make the total current draw with the Klee and other 3 modules installed to be about 770mA so should have just over 0.5A to play with but only 3 power slots left....third dizzy possible ??? seriously, i just don't get it
kecked
PICTURE PLEASE. MP3 PLEASE.................
Synthbuilder
satindas wrote:
I'm wondering if/how I can add a third dizzy.


Nice system. thumbs up

Yes, you can add as many Dizzies as you wish. The key thing to remember is that one shouldn't daisy chain the Dizzies' power inputs - just take each one back to the PSU and keep those wires as short as you can. You can fit two reasonably thick wires into those four way screw terminals, so fitting up to four Dizzies is straightforward.

Just remember though, don't push the PSU all the way. If you can in theory take 1.3A, it's probably a good idea not to take any more than 1A. This gives you some headroom because, once the modular starts getting patched, the current consumption can rise above that calculated from the individual current draws of each module.

And just because your power supply can handle the current doesn't mean to say that it won't get too warm if your heatsink/air flow is not sufficient. In other words, it may be a good idea to keep reviewing the situation as you add more modules.

Tony
SepticUnderground
I went from two dizzy to one dizzy because of the heating.


I use the CPSU + Yamaha PA-20 PSUs for all my racks


I burned my fingers touching the heatsink when installing a new CPSU + dizzy set next to it.

I went back to one dizzy each per CPSU and no more burning now...temp is now about 40 degrees Celcius, when it was more like 80-90 degrees before.

Dunno what should be max temp to be safe, I guess 60-65 degrees celcius might be okay.

So I power now 40U with 2 CPSus and 2 Dizzys in total per rack
Synthbuilder
SepticUnderground wrote:
I Dunno what should be max temp to be safe, I guess 60-65 degrees celcius might be okay.


A quick rule of thumb: if you can't touch it comfortably for more than ten seconds it's too hot (and probably over 60C).

The Compact PSU wasn't really envisaged to work with extra Dizzies. The general plan of that one was to power a row of modules in 19" rack - eg. midiDAC, two VCOs, a multimix, a core VCF, and two ADSR/VCAs. However, I know of a lot of folk who are using the CPSU successfully with a Dizzy. Just keep them cool...

Tony
satindas
Pics posted. new thread
MP3's soon
Synthbuilder
satindas wrote:
I've used the PA30 with 0R47 resistors on the PSU board and should therefore be ok up to about 1.3A. I make the total current draw with the Klee and other 3 modules installed to be about 770mA so should have just over 0.5A to play with...


I've been reviewing all my power supply work over the last two days. Unfortunately, not everything is correct. Because of this I have re-written sections of my User Manuals to reflect this new and hopefully better way of looking at things.

I was also not making it clear enough in the User Manual for the PSU that you cannot increase the current capacity of the PSU module by simply adding a different power pack and changing the current limit resistors. A change must also be made to the heatsinking arrangements. The 3U master panel design has only been tested with the PA-20 and this has a current limit considerably lower than 1.3A.

Now I notice Simon in your picture thread that you have the standard 3U panel design. This is not big enough to allow the PSU to supply 770mA. I have not tried it at that current but there is a high probability it will get too hot.

Secondly, on more careful reflection the 1.4A rating that the Yamaha boasts is an AC rating not the final DC output capability of the connected PSU. Once the PA-30's output is rectified and smoothed the total current drawn on this supply cannot exceed 0.8A.

So if you do see yourself taking 770mA then I would advise you to mount your PSU power devices on a suitably large heatsink - preferably on the rear side of the modular. The PSU module itself can probably stay where it is so long as the new heatsink is situated close by.
I am sorry about any confusion my ignorance has caused. I will now do penance... The MSN Smack!

Tony
jbi
Tony,
My build is going to be a similar size to Satindas and I have the same psu as him. If I assume I'll need a similar power output, what size heatsink would you recommend to fit to maintain a suitable temperature ?

I'll be getting the case soon and I'd like to get the psu fitted correctly before adding the modules.

Cheer,
John
nerdware
Now you've got me thinking about using a fan to cool the heatsinks. hihi However, all the silent fans I know run off a +12V supply...So unless they can also run off +15V, I can imagine a smaller PSU for the cooler for the big PSU. lol Actually, I'd want to use a fan speed controller, which I expect is really just a pot. So maybe +15V will be no problem. I have some old fans I could test this on...

The fans I've used (in computers) are usually quite large. E.g. 12cm and 14cm. They're designed for the heatsinks that cool CPUs. I've no idea how effective they'd be for synth PSU heatsinks, but I'd love to find out!

I also wonder about using a 19" blank panel for mounting the PSU at the rear of a rack. How well would that work as a heatsink panel? Has anyone tried that?
Synthbuilder
jbi wrote:
what size heatsink would you recommend to fit to maintain a suitable temperature ?


I may not be the right person to answer that question... eek!

I tend to build my own bigger PSUs in their own big metal rack cases where the case itself is the heatsink.

Now each power device is going to be dissipating around 11W with a current draw of 1A. There's 11V or so across each device worse case.

I reckon you are going to need a heatsink of at least 1.75C/W. And it'll probably be best if you can use 1C/W.

This may work:

http://uk.farnell.com/h-s-marston/44dn-01000-a-200/heat-sink-1-2-c-w/d p/148117

But I haven't built with this so I cannot verify it works.

I'm going to get up to speed on power supplies and see if I can work out something better in the next few months. The 19" rack users need something really good.

Tony
nerdware
Synthbuilder wrote:
I'm going to get up to speed on power supplies and see if I can work out something better in the next few months. The 19" rack users need something really good.

thumbs up Thanks!
kecked
http://www.heatsinkusa.com/

I'm using one of these as my back plate on a synthesisers.com 22 space cabinet. Overkill to be sure.

I did a test using an 1/8" plate that is 8"x8" and put a 2amp load on my power supply for 20 minutes and it stayed pretty cool. felt like someone with a fever.
jbi
Thanks for the comments. I'm just completing a PAiA MIDI2CV module with a 5U panel (will post piccies when completed). It claims to consume 200mA on the +ve rail and around 5mA on the -ve so that kind of blows the power budget. Fortunately the board includes its own psu so it is intended to run from a 12v AC supply as an alternative to a dual rail DC. I'll probably get a separate 12v AC supply for that module alone so as not to stress the Oakley psu for the rest of the modules.

John
Synthbuilder
nerdware wrote:
I also wonder about using a 19" blank panel for mounting the PSU at the rear of a rack. How well would that work as a heatsink panel?


Again it depends on the size of the panel and how much current draw you have in your modular. Flat panels don't really make good heatsinks and they are not going to work that well if you back the modular up against a wall.

However, if the panel is big enough and the current draw not excessive it will work. The question is how big does it have to be for a certain current?

Tony
nerdware
Synthbuilder wrote:
However, if the panel is big enough and the current draw not excessive it will work. The question is how big does it have to be for a certain current?

Sorry for being a bit vague. Ok, here are some numbers. A 5U 19" panel with an Oakley LN PSU with a PA-20, and a 500ma load.

Thanks.
Synthbuilder
nerdware wrote:
A 5U 19" panel with an Oakley LN PSU with a PA-20, and a 500ma load.


Yes, I think that will work fine. You should be able to put the two Dizzies on there too, as well as a standby switch and power inlet socket.

I'm going to have a go at building a PSU on a 4U 3mm aluminium 19" blank panel at some point and see how that does.

Tony
nerdware
Synthbuilder wrote:
nerdware wrote:
A 5U 19" panel with an Oakley LN PSU with a PA-20, and a 500ma load.


Yes, I think that will work fine. You should be able to put the two Dizzies on there too, as well as a standby switch and power inlet socket.

Excellent, thanks. I was thinking of putting at least one of the Dizzies on the same panel, plus the other bits. razz

Quote:
I'm going to have a go at building a PSU on a 4U 3mm aluminium 19" blank panel at some point and see how that does.

thumbs up

The whole heatsink business was puzzling me. I was thinking about using a 2U rack case just for the PSU, then mounting the Dizzies on the rear. (Very much like your one on the Oakley site, but using a PA-20.) I still like that option, as it brings the Dizzies closer to the modules, but it obviously adds to the cost. I feel a lot better about using a blank panel now. Thanks!
satindas
jbi wrote:
..... PAiA MIDI2CV ..... claims to consume 200mA on the +ve rail and around 5mA on the -ve ....
John


Ok... so the Midi2CV will run off dedicated PSU which will decrease my proposed current draw to around 570mA. I'll get round to remounting the power devices on heatsinks if necessary but if I'm down to 570mA and a max of 800mA with the PS30, that still leaves around 230mA to fuel the remaining 10 spaces in my case (and I still need a bunch of multi's). No worries. thumbs up
kecked
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=237-1 334-ND


2 amps solid. You figure out the wiring. I am NOT responsible if you kill yourself.
jbi
Whilst not as graphically stunning as Cerberus, my first build version has similar functions (but without the Klee). So my power solution is a big aluminium panel at the back with the PSU board mounted on it rather than the 5U front panel. A finned heatsink for the power trannies attached to the big panel. 2 dizzies with holes prepared for a third. If that gets hot then something really is wrong.
John
Paradigm X
Synthbuilder wrote:

I'm going to have a go at building a PSU on a 4U 3mm aluminium 19" blank panel at some point and see how that does.

Tony


Is this the recommended heatsink at the moment? Ive searched all the threads i can find about heatsinking and wasnt sure. Sorry for all the questions.

Im just on metal supermarket and wasnt sure whether to get 1.5mm folded steel or 3mm aluminium.

Cheers, Ben
Synthbuilder
Paradigm X wrote:
Is this the recommended heatsink at the moment? Ive searched all the threads i can find about heatsinking and wasnt sure.

The latest Builder's Guides and User Manuals for the PSU will give you my recommendations. As stated earlier in the thread those guides were revised considerably last year and more has been added since this thread was started.

There's a bit too much information to put in a forum post so have a look in those guides for more detail.

Paradigm X wrote:
Im just on metal supermarket and wasnt sure whether to get 1.5mm folded steel or 3mm aluminium.

Go with 3mm aluminum. It's easier to work with too.

Tony
Paradigm X
My apologies, ive read the builders guide a number of times but not the user guide.

Thanks
gtxdude
I could chime in on this one too... I have just finished my build as well, about two weeks ago. It includes the following:

midiDAC
VCO X3
VCO Controller
Comp & Gate Delay
Multi Mix X2
VC LFO X2
Triple LFO
COTA Filter
Trans Ladder Filter
Diode Ladder Filter
Journeyman Filter
SVF Filter
Croglin Filter
ADSR/VCA X3
VRG
FourMix
EFG Deluxe
Noise/Filter
Sample/Slew
RM-4014
Deep Equinox
Overdrive
Discontiniuty

This combination draws +800ma and -600ma @15v.

I used the Oakley standard power supply with a toroidal xfmr rated at 36v center tap @ 2.2 amps. I mounted this on a 7U X 5U 3mm panel. The pass transistors are mounted on the largest horizontal TO220 heat sinks that I could find and topped off with some small 15v fans (very quite).

This combination runs warm. The front panel below the positive pass transistor gets quite warm, but you can keep the back of your hand on it without discomfort. I left the unit powered up for 18 hours during a shake down session with no problems. I have 3 dizzy PCB's providing power to the modules.

Tony's power supply is rock solid in my configuration.
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