Low voltage connection basics
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[edit] What is AC voltage?
AC voltage is voltage that does not have a Plus and Minus terminal on the supply.
AC voltage symbol: 
Other names for AC voltage:
- Directed power or voltage
- Sine wave power or voltage
- Inverter type of power or voltage
[edit] AC voltage safety
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.
[edit] What is low voltage?
Other names for low voltage:
- Shock free power or voltage
[edit] What is DC voltage?
DC voltage is voltage that has a Plus and Minus terminal.
DC voltage symbol: 
Other names for DC voltage:
- DC power or voltage
- Battery type of power or voltage
- Plus-minus power or voltage
[edit] Electric DC polarity: plus and minus
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.
| sign on power output | or this sign | sign on power consumption | or this sign | harmful for output ? | harmful for power consumer ? |
|---|---|---|---|---|---|
 |
 |
|
|
no | no |
 |
 |
|
|
no | no |
|
|
|
|
no | YES ! |
|
|
|
|
no | YES ! |
|
DC | |
AC | no | YES ! |
|
AC | |
DC | no | YES ! |
[edit] Electric current ampere
| 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 |
[edit] Electric voltage
| 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 ! |
[edit] Adapter with different connectors
Protect your power supply.
On the left is the power supply output and on the right power receiving device.
.
Plus and minus
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
[edit] Type A USB
Add a picture with positive and negative labeled (in red (5+) and black) on a female Type A USB connector. File:FemaleUSB.pdf
Female, Type A,USB connector with pin diagram.
[edit] What is an electrical short?
An electrical short is when the plus and minus are in contact with each other.
This is harmful for the adapter or battery.
[edit] Electrical short with (dis)connecting device
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.
Right
[edit] Car cigarette lighter plug
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.
[edit] See also
[edit] Interwiki links
external links
