Likbez - What are the plus and minus voltage.

<b>Likbez</b> - What are the plus and minus voltage.

       What is a plus?

   This ministateyka was born in the writing
articles about the protection of SH-shki and could be its
part, but considering how I blew up that article,
decided to make this theme otdelno.Statya
 written "just in case."

   Maybe someone misunderstood something, or confused,
at least from what will come ...



             Pros and cons.


   What are the plus and minus voltage - this
only the relative values of the potentials, which can be 
arbitrarily taken at any place of some scheme. Recoverable 
simple 48k Speccy. His food - only 5V.

And PLUS 5V ... However! Watching how to measure ... If we take 
this very, plus a base, then all the voltages on the board, and 
the voltage Food, too, will be LESS!




  ---------- +5 Volts, + food --------


      Working area, the voltage in the circuit


 - Common wire, screen, 0 volts, minus -


   The above is a graphical representation of the potentials 
48go Speccy or any similar device. Moreover, lower line mean - 
less and negative, potential relative to the higher -

which means more positive and
potential.

   Figure consists of 3 parts: upper,
bottom line, and the zone between them.

   As can be seen, the highest potential has plus power supply: 
+5 V Above it is nothing no (in the Speccy, but not in its 
power supply) and all signals company (and its negative supply,

of course) are lower and have less capacity - that is, will be 
negative relative to plyusa.Takim, the upper line - an absolute 
plus, the highest potential of the system. 

   Working Area companies - a zone of zeros and ones analog R, 
G, B image signals and anything else that can compete on

plate.Razumeetsya, 1tsy lie almost at the
plus - is higher than 0, which lie almost
the bottom.

   At the very bottom (last line) there is less power - he's 
the general, who is also the screen for those who are not lazy, 
he is GND (as taken on imported schemas), it is 0V, and

he's a minus 5 volt power supply ?!?!?! Were you surprised 
these signs? let's see ... 

   If there is a plus, so there is a minus. Undoubtedly, the 
disadvantage is to minus 5V supply - the 5, and THAT is a plus! 

   Ask how else? A possible way!
After all, everything is relative ... And less, too ... He
been and will be minus, plus the relatively
supply and relatively 0V. Of course, we
you know that the 0V and minus power Speccy
- Are the same, and, of course, the same and
minus 5V, BUT! with a caveat: "with respect to
plus food. Shibko literate people, not
familiar with the Speccy - mind you - it is quite logical (and 
I understand them) may not count exactly (to put it mildly), 
voltage, or (even worse) get lost in the basics of electronics 
and physics, which state: Voltage is the potential difference!


   Now imagine some Vasya, who in his life except for trinkets 
payal mikruhah CMOS process, and nothing about the TTL

do not know. Glancing at the diagram and seeing Speccy
inscription +5 V and-5V, he pretend to be the very
potential difference, calculating the voltage
Power: Upitaniya = +5 V (-5V) = 10V! A lowered
eyes and see the familiar K561LN2 (generator
FLASH TAPE interface and the 48th company) -
Of course, it may take control at parity,
because K561LN2 collected from the known to him
CMOS technology allows floating food - beyond any standard in 
the range: 5Ў15 current and reasonably Calculated 10B as

Once these limits are placed!

   Fortunately, the burn Speccy grief-markers
unlikely udastsya.Vo First, he finds the potential 0V required 
for bipolar food, or take him all the same minus 5V, and a 
source of negative korotnet voltage, in the end, suspecting 
something was wrong, sort out what's what ... 

   The idea is that you need to be clear about those same 
potentials, advantages and disadvantages, and be very correct 
in drawing and description schemes. 

   Since TTL logic is considered
as the logic of the positive +5 V
+ / - 5% (for K1533 Series + / - 10%), no
minus 5V on the scheme can not be. There
0V, zero potential, which is a common drawback of all 
TTL-compatible chips this system (except obviously outside the 
box included, which will be obvious if they are in the scheme 
at all). 

   If we are risen +5 V supply
as a common wire, as 0V (ie take it
for 0), then, of course, less power will be
be-5V. Again, quite logically,
potential difference: 0V (-5V) = 5V - normal power supply. It's 
all clear from the graph drawn above. Can be defined as 0V plus 
and minus as-5B; can designated as a +5 plus and minus as 0V;

What will be the same anyway? Of course, difference, difference 
potetsialov that will be 5V supply voltage - adopted

as the standard for TTL, and TTLSH AND A ¤ Technology
chips, and the same stringent standards
is a positive polarity power supply
and the signals of these mikroshemm. Physically, a
wire can be 0V, and the other either +5 V
or-5V, but the standard adopted by the +5 V relative to 0V, and 
nothing else! 

   Therefore, in our scheme the potential power and common wire.

   Common wire can be specified as 0 V or
GND, and may be omitted altogether if the
scheme is the notation:



   It will be taken as a common wire.

   Less correctly indicate the sign of the total
wires - just a plus or a minus, without specifying volts. Of 
course, a sign of some sort is (If the device is unipolar), but 
also because obvious, as opposed to the potentials. Sign again 
indicates very common wire that is easier than writing 0V,

or GND. But the sign does not always coincide with
sign the common wire of the device to
that connects to your scheme.

   It seems that in his scheme of the encoder, I have
+12 V supply, and negative - as common.
This is not quite correct, but as a rule,
Speccy only two sources: +5 V and +12 V,
disadvantages which are connected and form a common
power cord - that is, in any case less
will be shared. But imagine a case ...

   Full AMIGnik procured himself AMIGA 500.
This model seems to be a black and white Video.I
decided to put myself coder to decorate it ... But here's the 
problem ... I have a minus, but what? rather, where? Most would 
find common wire for Ami, but through the eyes of the simple 
user - minus to Ami as such, no! There is the potential-12B, 
there is GND - common wire, it is 0V, but just a minus sign (as 
in Speccy) No!


   For example, there are chips - the most
fastest of all that were released earlier this
ESL Technology - emitter-coupled logic (K500 series, sort of). 
They have a negative Diet and negative signaly.Esli paint 
scheme with mikruhami, it should correctly specify the cord - 
both potential-5.2V (this is, like, there is tension), and 
overall not as +, but as 0V or GND. Common wire of the device, 
when connected to the Speccy (no idea who this is may be 
needed), will connect to 0V. Given that the overall Speccy with 
his food - it's a minus, but overall this ECL device with its 
power - is a plus. 

   In the case of any exceptions when
common wire of the device is connected to the non-public wire 
of any other devices - is indicated on the diagram, or

indicate the potential use of input /
output signals. For example, if the ECL device built to Speccy, 
and takes its signals, which are designated as inputs

and negative, it is clear that the ECL Plus devices must 
connect to +5 V Speccy, as only about +5 V TTL signals

Speccy can be otritsatelnymi.Opyat same
can not imagine such a device, but theoretically everything is 
possible. 

   Therefore, you should specify the common wire
as GND or 0V, ie, unsigned supply
voltage (one or more of which
required for the scheme) with a sign.

   Well, if the above
notation can be no common wire
ukazyvat.V latter case, the semi-literate
users turn to zhelezyachniku that easily sort out (if good 
zhelezyachnik), but if not sort out - not fate shall learn (be 
zhelezyachnikom). With For my part I will try to be more 
correct in their schemes. 



  It has been almost July 2003. KSA-7G.