At 11:00 PM -0500 09/01/02, Paul Schreiber wrote:
>
>I'm starting to worry about current draw of some digital-based MOTM-500
>series modules.
Cool, that's means you are working on them :)
>I want to use nice LED alphanumeric displays for some of the modules. LCD
>needs a backlight, and that also sucks power. How much power? The uP(s) +
>>displays are at about 300ma to 400ma.
I agree, LED is way better than LCD.
>Of course, I can add a +5V regulator to the +15V line, but that sucks all
>your +15V current.
As I'm sure you already know, there are voltage inverting switching
regulators, but running off the -15V doesn't sound like a good idea either
(not to mention the cost and complexity added to each module).
>So, what I am thinking is using a "line lump" +5V switcher. These have
>"universal inputs": they will work anywhere in the world without a jumper.
>>The plug is a standard-sized 'barrel' female.
That sounds like a good idea.
>I would have a 1U panel made up with
>
>a) panel-mounted male connector
>b) power LED
>c) auto-power switch: the +15V turns on the +5V
>d) a new distribution board with 3-pin MTA connectors
Would all that be necessary?? I don't see the advantage of having a panel
if the switch is auto. Nor do I see the advantage of having a power LED if
these modules have LED displays.
While I realize it's the wrong way to distribute +-15, perhaps a
daisy-chain system would work for +5V. The back of each digital 500 module
could have two "line lump" jacks wired in parallel.
Then people could plug their linear supply and their +5 switcher into the
same power strip, and use that to turn everything on and off.
Even if an auto-power switch is necessary, it still does not require a
panel. It could be mounted on the distribution board behind the scenes,
which, imho, would be much more elegant.
>Also, it may be possible to take the +5V input and on the
>module, convert to +-15V just for ∗that∗ module's use. The reason is that
>the current for +-15V is usually on the order of 20ma. Another thing to
>>consider is that the 500 Series modules are not
>"clean" like say a VCO or VCA is. If there is some local power supply
>"grunge", that DOES NOT find it's way back into the "clean" supply, you
>>will never "know" it was there in the first place
>(how 'clean' does a fuzz box need to be?).
(That's a very difficult question to answer. Imho, there is a huge
difference between distortion, and hum and noise.)
>There is 1 more solution: a 3U wide MOTM-950 Supply. It's got all 3
>voltages BUT the +-15V is lower current: 400ma instead of 800ma. This is
>>used to power 500 Series ONLY. The 500 Series would use a 6-conductor
>>MTA-156. The +5V is rated at 2A. This could power between 5 and 8 500
>Series.
I guess that would be OK for someone who wants an all-500 system, but even
they might want to add some non-500 modules as well -- perhaps an LFO or a
couple of envelopes as mod sources.
Also, the 500 modules might bring new people into the system. Let's say
people who don't have any MOTM buy 500's in order to add new and different
modules to their setup. Then when they realize for themselves all the
advantages that are hard to convey through a website -- ergonomics,
precision, build quality, convenience of 1/4" jacks, etc. -- they might
want to buy more MOTM. However, they might be less likely to start adding
non-500 modules if they have to buy another power supply.