Low voltage connection basics
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 What is AC voltage?
AC voltage is voltage that does not have a Plus and Minus terminal on the supply.
Other names for AC voltage:
- Directed power or voltage
- Sine wave power or voltage
- Inverter type of power or voltage
 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.
 What is low voltage?
Other names for low voltage:
- Shock free power or voltage
 What is DC voltage?
DC voltage is voltage that has a Plus and Minus terminal.
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
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 ?|
 Electric current ampere
| amp. on
|or this amp.|| amp. on
|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
|volt output||volt consumer|| harmful for
| 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
Protect your power supply.
On the left is the power supply output and on the right power receiving device.
Plus and minus
|Shortcut|| Plug Type
(*) Mono jack
 Type A USB
 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.
 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.
 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.
 See also