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Low voltage connection basics

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AC voltage safety[edit]

AC electricity with a voltage less than 50 V (RMS) is called Extra Low Voltage. This voltage is unlikely to give a human being a dangerous electric shock.

What is low voltage?[edit]

Other names for low voltage:

  • Shock free power or voltage

What is DC voltage?[edit]

DC voltage is voltage that has a Plus and Minus terminal.

DC voltage symbol: Plus min power.PNG

Other names for DC voltage:

  • DC power or voltage
  • Battery type of power or voltage
  • Plus-minus power or voltage


Electric DC polarity: plus and minus[edit]

Electricity basics: Marked plus wire

For most kinds of devices it is important to have the right voltage and polarity. Wrong voltage or polarity can destroy a device

How to mark the plus or to find the plus pole:

  • Red is always plus.
  • Painted line on the plus wire, no painted line on the min.
  • Square wire is plus, round wire is minus.
  • Sharp edge is plus, round wire is minus.
  • Knot is plus, no knot is minus.
  • Mark on the plus wire, the plus wire is special.
  • and so on, the plus wire is special or not normal than a normal wire.


These must be in good working order to save your electric material:

  • The voltage.
  • The amperage.
  • The plus and minus position.
  • The type of power, AC or DC.
  • The type of low voltage coax connector.
  • Protect your plug and connector against mechanical pulling force.
  • Take your time to check these 6 items.


Side and middle electric connection


sign on power output or this sign sign on power consumption or this sign harmful for output ? harmful for power consumer ?
Inside MIN outside PLUS.PNG Outside PLUS inside MIN.PNG Inside MIN outside PLUS.PNG Outside PLUS inside MIN.PNG no no
Outside MIN inside PLUS.PNG Inside PLUS outside MIN.PNG Outside MIN inside PLUS.PNG Inside PLUS outside MIN.PNG no no
Inside MIN outside PLUS.PNG Outside PLUS inside MIN.PNG Outside MIN inside PLUS.PNG Inside PLUS outside MIN.PNG no YES !
Outside MIN inside PLUS.PNG Inside PLUS outside MIN.PNG Inside MIN outside PLUS.PNG Outside PLUS inside MIN.PNG no YES !
Plus min power.PNG DC NO plus min power.PNG AC no YES !
NO plus min power.PNG AC Plus min power.PNG DC no YES !

Electric current ampere[edit]

amp. on

power output

or this amp. amp. on

power consumer

or this amp. harmful

for output ?

harmful for

power consumer ?

500 mA =0.5 A 500 mA =0.5 A no no
400 mA =0.4 A 500 mA =0.5 A YES!* no
500 mA =0.5 A 400 mA =0.4 A no no

* - Depending on how your output device is made, this condition may cause the output device (usually some kind of wall plug adapter) to burn out. The better made ones will have some sort of over-current protection built in, either in the form of a thermal fuse (self resetting), or a current limiter.

Electric voltage[edit]

volt output volt consumer harmful for

output ?

harmful for

power consumer ?

12 V 12 V no no
9 V 12 V no does not work well
3 V 12 V no does not work
12 V 9 V no YES !

Adapter with different connectors[edit]

Protect your power supply.

On the left is the power supply output and on the right power receiving device.


.

Inside outside size.PNG

Plus and minus

Power supply with connecting adapters.PNG


Adapter connectors

OUTSIDE

(mm)

INSIDE

(mm)

Shortcut Plug Type

(code)

mark
6.5 1.0 no AA =
6.5 1.75 no AB =
2.5 2.5 YES! A (*) =
3.5 3.5 YES! B (*) =
3.0 1.0 no C =
5.0 2.1 no D =
5.5 2.1 no E =
5.0 2.5 no F =
5.5 2.5 no G =
3.5 1.35 no H =
4.0 1.7 no I =
4.75 1.75 no J =
5.0 1.5 no M =
5.5 1.5 no N =
5.5 5.8 no P =
6.3 3.0 no Q =
7.0 1.0 no R =
2.35 0.75 no S =

(*) Mono jack

Type A USB[edit]

Add a picture with positive and negative labelled (in red (5+) and black) on a female Type A USB connector. FemaleUSB.png


What is an electrical short?[edit]

An electrical short is when the plus and minus are in contact with each other.

This is harmful for the adapter or battery.

Electrical short with (dis)connecting device[edit]

Some smaller connectors shortcut the power supply if you (dis)connect .

(dis)Connect the connector to the device if there is NO power on the plug.

WRONG CONNECTING DEVICE.PNG


Right

Connecting device.PNG


Car cigarette lighter plug[edit]

A car cigarette lighter plug must have the plus in the middle and the minus on the outside.

Some female car sockets have 24 volts.


Car cigarette lighter DC Plus and Min.PNG

See also[edit]

Interwiki links[edit]

external links