Basic Rules of electricity
when selecting a power supply.
- 1. Check the label
of the device you wish to power for the spec and Note -
- The Voltage -
- (Voltage Volts (V)
is sometimes specified in fractions i.e 19.5V or 19.5
Volts).
- The Current consumption -
- (Current is specified in Amps (A)
OR milliamps mA,
1000mA = 1 Amp or 1A).
- The connection POLARITY -
- (usually POSITIVE (+Ve) Centre Pin
BUT NOT ALWAYS).
- 2.
Check the size (and Type) of the connector -
- There are many 'common' connectors from thousands available,
Don't 'assume it will fit'.
Selecting a power supply -
- The OUTPUT Voltage must
ALWAYS Match1,
2
- The OUTPUT Current must
ALWAYS be Equal
OR Greater to the device3
- The Polarity must
ALWAYS be the same4
- When using voltage selectable supplies
ALWAYS Select
the voltage and polarity BEFORE
connecting to the device.
- 1
If you connect a supply with (OR Set) to a higher voltage one of the following may happen -
- a) The excess VOLTAGE will probably damage your device.
- d) The excess VOLTAGE may cause excessive CURRENT demand, Overloading the power
supply and the device or both.
- c) Some devices may operate perfectly until they FAIL due the excess voltage overstressing
components.
- 2
Too LOW VOLTAGE can also problems -
- Too Low Voltage power supply may not operate the device correctly.
- Too Low Voltage on some devices with secondary internal switch
mode power supplies (common in many modern devices), the the device may well operate perfectly BUT
the low voltage causes More current demand, if the power supply cannot supply this current then
3 apples.
- 3
If you connect a supply with too low a current rating for your device several things may happen. The excess current demand will overload
the rating of the power supply which could cause several different scenarios -
- a) The power supply may
have overload protection and cut the output, Appear as DEAD, But it's NOT.
- b) The power supply may
still output but at lower voltage casing incorrect operation of your device.
- c) The power supply may
Work but be over stressed and fail.
- c) The power supply may
Work but be cut out and restart when cooler.
- e) The power supply may
overheat and - Fail, Blow a thermal fuse, worst case Cause a FIRE!
- 4
If you connect a supply with the wrong polarity then -
- There is a high probability of damaging your device !
- Best case is the device has diode input protection and the device will just appear
to be dead.
- Rare but some devices could short circuit the supply
output causing overload as in3.
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