Specifications

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the current-limiting resistor and the Zener diode used. It is also compact, and
should be able to withstand the various requirements previously specified.
The disadvantages are that due to its simplicity, it offers no additional protection
against short circuit current or excessive levels of voltage. Zener diodes can be
destroyed if their maximum voltage and/or current tolerances are exceeded,
rendering the circuit useless. A significant disadvantage of this circuit is its
inefficiency. Any additional voltage simply gets turned into current and shunted to
ground. While this produces the desired output, it is not an efficient use of
available power.
In addition, it offers no additional advanced protections, such as short circuit
protection across the output terminals. While this is not a requirement, it would
be an element of good design to make as robust as possible a solution within the
given cost, size, and implementation restraints.
2.3.3 Voltage Divider Based Solution Using Resistors
Another simple option would be to use a basic voltage divider with resistors. It
would use the well known method of dividing voltages in order to convert 12Vdc
to 5Vdc usable by the circuit. This design is also perhaps the most reliable.
However, it offers no additional regulation – any fluctuation in the input voltage
would be immediately realized at the output voltage proportionally, according to
the ratio of resistors used. In addition, the additional voltage is dissipated in the
resistors, resulting in power inefficiencies and excess heat.
2.3.4 Pre-Built 5Vdc Regulator Circuit Boards
A more robust solution would be to use a professionally designed and assembled
voltage regulation board. While there are many such solutions, one possible
solution is a Dual Output 12 & -5 Voltage DC Regulator Kit produced by EID
Corporation. An image of the board can be seen in Figure 2.2.4-1. It is capable
of accepting 14 to 24 Vac or (+/-) 14 to 24 Vdc input. It then outputs two
regulated voltages of 12 Vdc and -5 Vdc.