MOTM

> Since I admit I know little to nothing in the world of power supplies, can
> anyone tell me if there is any way I can turn a +12VDC power supply into a
> +-12VDC power supply? Maybe this is impossible, I don't need much current,
> just enough to run a keyboard circuit. Let me know... Thanks. -Nate

HA! One of my famous lectures coming on.

The *first day* I was in EE lab, I saw a little HP bench supply. It said "DC
output 0 - 20V".
There were 3 terminals on the front, marked +, -, and G. Whipping out
Electronotes #6
(this shows my age), I decided to build something.

Well, I carefully hooked everything up (it was a LFO, I think), power up,
and NOTHING.
I sat there for about 45 minutes doing my Stooge Larry imitation, looking at
each connection,
ohming-out each resistor (I was a little iffy on the color code). Yep, it
was all correct.

About this time the lab instructor wanders over, looked over my stuff and
sort of half laughed
and half sighed. He then pointed out that the HP was only outputting +15V. I
said "Look, it
has a minus terminal!". He calmly explaind it wasn't *really* minus, but
ground. I then
blurted out "What's this friggin' GROUND TERMINAL connected to?". Oh, that
was a *different*
ground, the chassis ground. At this point, switching majors back to physical
chemistry looked
*REAL* appealling.

The moral of the story: To get +-12V, you really need a 24V *total
potential* and you are
calling "ground" the middle point. What a "negative" voltage means is that
the ground is
*above* it by 12V.

So, the only way is to use the +12 to drive a switching inverter IC. Look at

www.maxim-ic.com

there are many there. The hard part will be getting the -12V. -5V is more
common. Also
look at Linear Tech's website. Maxim and LT parts are available from
Digikey.

As a former boss said, "Ground only exists in the basement of Bell Labs"
which he liked to
shorten to "Ground is in New Jersey!" anytime anybody in the lab said
'Ground' out loud.
In telcom, you say "Earth potential".

One day, I shall relate another "Ground" story about my first "real job"
measurement, that
caused me to blow up (literally) a $4500 scope.

Paul S.
((Boss's other favorite expression: "No matter how hard you try, you can't
polish a turd."))

>As a former boss said, "Ground only exists in the basement of Bell Labs"
>which he liked to
>shorten to "Ground is in New Jersey!" anytime anybody in the lab said
>'Ground' out loud.
>In telcom, you say "Earth potential".

We call ground ground.  But the return from the negative battery
feed is called return, not ground.  Just like neutral is not called
ground in a home electrical system even though it is connected
to ground at the main breaker panel.  The returns from equipment
in a CO are connected to ground at the main battery power
distribution frame.  What really throws the new guys is that +
goes to ground and - goes to battery.  Boy have I seen some good
arc welding.  Good thing Craftsman has a lifetime warranty on
tools.

-Cary

>
> We call ground ground.  But the return from the negative battery
> feed is called return, not ground.  Just like neutral is not called
> ground in a home electrical system even though it is connected
> to ground at the main breaker panel.  The returns from equipment
> in a CO are connected to ground at the main battery power
> distribution frame.  What really throws the new guys is that +
> goes to ground and - goes to battery.  Boy have I seen some good
> arc welding.

HA! This begs the question (to all you EE-wannabes), "why is it done this
way?"

Hint: it has to do with *chemistry*, not "electronics".

Paul S.

>HA! This begs the question (to all you EE-wannabes), "why is it done this
>way?"
>
>Hint: it has to do with *chemistry*, not "electronics".

[waving arm in air] 

I know.  I know.  Pick me.  Pick me.

It's because electrons are negatively charged and flow from -
to +, contrary to common misconception of + to -.  I think the
military teaches it the right way.

-Cary

> >HA! This begs the question (to all you EE-wannabes), "why is it done this
> >way?"
> >
> >Hint: it has to do with *chemistry*, not "electronics".
>
>[waving arm in air]
>
>I know.  I know.  Pick me.  Pick me.
>
>It's because electrons are negatively charged and flow from -
>to +, contrary to common misconception of + to -.  I think the
>military teaches it the right way.
>
>-Cary


I can pipe in here.  In the past 10 years the Nuclear navy has switched the 
way they teach this a half dozen times.  I learned it as "electron flow" 
(conventional current flow) + to - in my electrician school.  Then in 
nuclear power school they said the Navy is going to start teaching "hole 
flow".  The idea was - to +.  The hole comes from the space left by the 
electron that just "vacated" a "hole".  WHATEVER.  The idea is there is a 
difference in potential (voltage) and without it there is no current flow 
whether it is + to - or - to+.  I love this conversation.  In the end it 
usually leaves those with any insecurities in there knowledge sure of only 
one thing - they don't know anymore.

The ironic part...  I teach this now and I teach the conventional current 
flow - many nubs, as we call them, understand + to minus easier despite the 
actual physics involved.

Steve...  still in Hawaii

steve@... writes:

>>I can pipe in here.  In the past 10 years the Nuclear navy has switched the 
way they teach this a half dozen times.  I learned it as "electron flow" 
(conventional current flow) + to - in my electrician school.<<

I was about to bring this up.  When I was in college 15 years ago learning 
this there was conventional current flow which goes from + to -/ground.  And 
there was electron flow which goes from -/ground to +, because that is the 
directions that the electrons actually move from atom to atom.  But since 
schematic symbols were created with conventional flow type thinking (from + 
to -) that seems like the way you should think.  You don't want to start 
questioning what direction your diode and transistor symbols should be 
pointing if you are drawing a circuit.

-Elhardt

> >Hint: it has to do with *chemistry*, not "electronics".
> 
> [waving arm in air] 
> 
> I know.  I know.  Pick me.  Pick me.
> 
> It's because electrons are negatively charged and flow from -
> to +, contrary to common misconception of + to -.  I think the
> military teaches it the right way.
> 
> -Cary

Bzzzzzzzzttt!

Wrong.

Paul S.

>
> > >HA! This begs the question (to all you EE-wannabes), "why is it done
this
> > >way?"
> > >
> > >Hint: it has to do with *chemistry*, not "electronics".

> I can pipe in here.  In the past 10 years the Nuclear navy has switched
the
> way they teach this a half dozen times.  I learned it as "electron flow"
> (conventional current flow) + to - in my electrician school.  Then in
> nuclear power school they said the Navy is going to start teaching "hole
> flow".  The idea was - to +.  The hole comes from the space left by the
> electron that just "vacated" a "hole".  WHATEVER.  The idea is there is a
> difference in potential (voltage) and without it there is no current flow
> whether it is + to - or - to+.  I love this conversation.  In the end it
> usually leaves those with any insecurities in there knowledge sure of only
> one thing - they don't know anymore.

Bzzzzztttt!

Wrong.

Paul S.

>
> I was about to bring this up.  When I was in college 15 years ago learning
> this there was conventional current flow which goes from + to -/ground.
And
> there was electron flow which goes from -/ground to +, because that is the
> directions that the electrons actually move from atom to atom.  But since
> schematic symbols were created with conventional flow type thinking (from
+
> to -) that seems like the way you should think.  You don't want to start
> questioning what direction your diode and transistor symbols should be
> pointing if you are drawing a circuit.
>
> -Elhardt
>

Bzzzzttttt!!!

Wrong.

Paul S.
handing out the zeros

It has to do with electrolysis. In a huge system like this, there will be
leakage current into the earth. The leakage is through wet phone wires. In
the process of electrolysis, corrosive action is confined to the anode or
positive side.  When the wires are at negative potential compared to the
ground the metal ions go from the ground to the wire instead of the
situation where positive voltage would cause metal from the wire to leave
which causes quick corrosion.

Do I win?

Tony

> -----Original Message-----
> From: Paul Schreiber [mailto:synth1@...]
> Sent: Tuesday, September 12, 2000 9:41 PM
> To: motm@egroups.com
> Subject: Re: [motm] More OT: PS Question
>
>
>
> >
> > We call ground ground.  But the return from the negative battery
> > feed is called return, not ground.  Just like neutral is not called
> > ground in a home electrical system even though it is connected
> > to ground at the main breaker panel.  The returns from equipment
> > in a CO are connected to ground at the main battery power
> > distribution frame.  What really throws the new guys is that +
> > goes to ground and - goes to battery.  Boy have I seen some good
> > arc welding.
>
> HA! This begs the question (to all you EE-wannabes), "why is it done this
> way?"
>
> Hint: it has to do with *chemistry*, not "electronics".
>
> Paul S.
>
>
>
>
>
>

We have a winner! (see, I said *chemistry*, not *physics*)

Paul S.

----- Original Message -----
From: "Tony Karavidas" <tony@...>
To: <motm@egroups.com>
Sent: Wednesday, September 13, 2000 12:15 PM
Subject: RE: [motm] More OT: PS Question


>
> It has to do with electrolysis. In a huge system like this, there will be
> leakage current into the earth. The leakage is through wet phone wires. In
> the process of electrolysis, corrosive action is confined to the anode or
> positive side.  When the wires are at negative potential compared to the
> ground the metal ions go from the ground to the wire instead of the
> situation where positive voltage would cause metal from the wire to leave
> which causes quick corrosion.
>
> Do I win?
>
> Tony
>
>
> > -----Original Message-----
> > From: Paul Schreiber [mailto:synth1@...]
> > Sent: Tuesday, September 12, 2000 9:41 PM
> > To: motm@egroups.com
> > Subject: Re: [motm] More OT: PS Question
> >
> >
> >
> > >
> > > We call ground ground.  But the return from the negative battery
> > > feed is called return, not ground.  Just like neutral is not called
> > > ground in a home electrical system even though it is connected
> > > to ground at the main breaker panel.  The returns from equipment
> > > in a CO are connected to ground at the main battery power
> > > distribution frame.  What really throws the new guys is that +
> > > goes to ground and - goes to battery.  Boy have I seen some good
> > > arc welding.
> >
> > HA! This begs the question (to all you EE-wannabes), "why is it done
this

> > way?"
> >
> > Hint: it has to do with *chemistry*, not "electronics".
> >
> > Paul S.
> >
> >
> >
> >
> >
> >
>
>
>
>

On Wed, 13 Sep 2000, Paul Schreiber wrote:

> We have a winner! (see, I said *chemistry*, not *physics*)

  Can I have any points if I say the words 'sacrificial anode'?

  (Many of these of which I had to install with power panels in factories)

Crow

/**/

I would've guessed electrolysis too -- if only do to Paul's hint. I had no 
idea about the corrosion problems averted by using a positive ground, but 
I've seen water mains corrode in a few years when the originals lasted about 
twenty -- until the plumbers change them out and remove the ground straps 
(job insurance I guess).

I'll also note that the house I currently live in (probably built in the 
thirties or forties) doesn't have ground = neutral. I found this out while 
recently swapping out some stereo components -- holding a tape deck in my 
sweaty hands when my sweaty arm rubs against another component (OUCH!). 
Apparently each side is about 60 V about the ground pin.

Sweat is a good conductor!
JB

In a message dated 9/13/2000 10:31:09 AM, tony@... writes:

>It has to do with electrolysis. In a huge system like this, there will
>be
>leakage current into the earth. The leakage is through wet phone wires.
>In
>the process of electrolysis, corrosive action is confined to the anode
>or
>positive side.  When the wires are at negative potential compared to the
>ground the metal ions go from the ground to the wire instead of the
>situation where positive voltage would cause metal from the wire to leave
>which causes quick corrosion.
>

Is the keyboard you are using a CV keyboard for your MOTM for example? If so, 
you may want to use the MOTM's Power One supply for accuracy's sake. 

My Serge TKB outputs 0 V at the low end and 5.03 V (according to my meter) at 
the high end and there is no trimmer. I've had to calibrate VCOs specifically 
for use with the TKB. So little differences in the output voltage are 
extremely noticeable if used for traditional pitch control.

JB

In a message dated 9/12/2000 7:53:19 PM, nate@... writes:

>Since I admit I know little to nothing in the world of power supplies,
>can
>anyone tell me if there is any way I can turn a +12VDC power supply into
>a
>+-12VDC power supply? Maybe this is impossible, I don't need much current,
>just enough to run a keyboard circuit. Let me know... Thanks. -Nate
>

You don't even want to get me started on grounding and stuff like that.  I
would say the single most common cause of equipment damage is improper
grounding techniques.  I've seen about every stupid thing you can imagine.
Now as a little piece of trivia, the only way to run multiple feed DC
systems used in utility system operations is UNgrounded. Examination of  "+"
to ground and "-" to ground floating voltage measurements can tell you LOTs
about stuff that is going wrong you don't even know about yet.

Larry H

Maybe to keep from growing all that funny looking stuff on the connections?

----- Original Message ----- 
From: Paul Schreiber <synth1@...>
HA! This begs the question (to all you EE-wannabes),
"why is it done this way?"
Hint: it has to do with *chemistry*, not "electronics".
Paul S.