In this page, we’re going to talk about linear voltage regulators and show you how to use one to charge 5 volt USB devices like phones and mp3 players.
So, what is a voltage regulator? A voltage regulator is a device that takes an unregulated input voltage that could be fluctuating over time, and spits out a perfectly regulated constant voltage.
For example, here we have a twelve volt battery that will be 13.8 volts fully charged, and around 11 volts fully discharged. This 5 volt regulator will ensure that we will get a constant five volts regardless of the input voltage.
And the capacitors in the circuit will maximize the stability of the regulator’s output. We wills how you the circuit on the bread board later on.
In the meantime take a look at the image at 0:47. In an earlier tutorial, we showed you how to make unregulated DC supplies. Right now the output of that unregulated supply is 16 volts with about 2 volts ripple on it. But if we have a 12 volt regulator, we get a constant 12 volts out, regardless of what’s happening in the input.
So you can buy a voltage regulators to get any voltage you want. And it’s really not much more complicated than that.
Basically you have a higher input voltage that could change anytime and the linear voltage regulator just clips all of that off, leaving you with a lower but very precise DC power supply.
Even a terrible linear voltage regulator will give you an an input that is accurate to within 5 percent. And newer voltage regulators have a thermal shutdown feature which means we can’t show you one catching on fire.
Now, how do we find the voltage regulator? Most voltage regulators begin with a few letters then “78” then they have two digits indicating the output voltage. Example an L7805CV. The 05 indicates that it’s a 5 volt regulator.