Simple Accessory Voltage Regulator

(for battery operated devices)

There are times when batteries in electronics are a pain in the butt, as they go dead at the most inconvenient times. Since a boat has a 12V battery bank and since our electronic gizmos run on a somewhat lower voltage, I thought a voltage regulator circuit was in order to have my boat battery bank run my electronics. There are a 100 voltage regulator circuits but I found that the least expensive solution was using a common 7805 fixed voltage regulator found at Radio Shack, it is possible to design a custom voltage output regulator for $2.00 which is current limited to slightly more than 1 amp. Most of the time, that’s all we require.

This regulator is desirable if you have a bunch of battery operated devices which accept an external power source. You can eliminate all your batteries as you can design any voltage you like between 5-10vdc as an output.


The base Formula for modifying the cheap regulator is
Vout = V(designed)\(1 + R2/R1) + (Iq * R2)
So, for a common 7805 fixed 5 volt regulator
Vout =5(1 + R2/R1) + (Iq * R2)
Where Iq = .0042 (4.2 ma) and you experiment with the values of R1 and R2

This design is inexpensive and works just fine but you do need a heat sink for the 7805.

An Example: For a regulated output of 9.35vpackage
Vout= 5(1+1000/33000)+(.0042*1000)
Use the following components
R133000 ohm
R2/VR11000 ohm

By Rick

Owner of a Catalac 8M and Catamaransite webmaster.

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