I
constructed this voltage regulator to power my two way mobile radio from the car
cigarette lighter circuit. It has many other uses and the voltage can easily be
adjusted by the use of a potentiometer. The voltage regulator is an LM317T, and
should accept up to about 14 volts without problems. It can handle up to 1 amp,
but you WILL need a heatsink on the voltage regulator.
The components are:
R1: 270R R2:
2K Cermet or carbon preset potentiometer C1: 100nF C2: 1uF tantalum
LM317T Voltage regulator Heatsink PCB board
I also added DC
power jacks for input and output on my voltage regulator, a green power LED, and
a red over-voltage LED. The over voltage LED uses a zener diode to switch on the
LED at a certain preset voltage, this can be varied depending on the voltage of
the zener diode, I used a 6.2v zener diode. If you plan to vary the voltage for
the different items you power, don't bother adding this feature. If you only
plan to use items that run on one voltage, this is a very useful feature and
will save plugging in and damaging your valuable (or not so valuable) equipment.
You can even add a relay to switch off the power if the over voltage LED turns
on, but bear in mind it will have to work from the voltage of the zener diode
right up to the input voltage. I couldn't add a relay because I couldn't find
any that operated from 6.2-13.8 volts. Anyway, the schematic is shown above, the
over voltage and power LED are not included in them because it is assumed that
anybody who makes this will understand how to use a zener diode:
This is
what the final product should look like inside:
This is an outside view of the finished
voltage regulator:
Here is what my voltage regulator is
intended to power:
