How to Build a Voltage Regulator for $3

Here’s a straightforward way to build your own “Runtz” type voltage reducers so that you can use your 6 volt gauges on your 12 volt system.

The regulator is based on the LM7806 integrated circuit, which is able to reduce voltage while maintaining a constant current. Use one regulator for each gauge; this allows you to keep each circuit separate which is useful for sorting any troubles you might have. While it is possible to use one regulator for all gauges using a power transistor, it has a bigger footprint and produces more heat, requiring it to be carefully mounted away from any heat sensitive parts.

Here are the components:

1x LM7806 voltage regulator
2x 1μ 25-35 volt tantalum capacitors
1x Heat sink (around one inch long)
3x wires cut to 3 or 4 inches in length

You will also need a soldering iron, solder, some pieces of shrink tubing, and a bit of heat sink paste.

First, bend the leads on the capacitors into an “L” shape. Usually the longer lead is the positive side and since we want to attach the positive ends to the outer leads on the LM7806, make sure the capacitors are bent in opposite directions.

With the LM7806 sitting with the tab side down, solder one capacitor to one of the outer leads of the LM7806, then solder the other capacitor to the other outer lead. Again, be sure these are the positive ends of the capacitors. Carefully bend the remaining lose capacitor leads to make contact with the center lead of the LM7806. Solder them in place.

Next, trim the three posts on the LM7806 so they are just long enough to solder the wires into place. First solder the center wire (ground), then the left (12V) and the right (6V).

Cut some short lengths of shrink tubing and slide them along the wires all the way to the regulator side and heat them. Then take a larger piece and wrap the three leads together. This will both insulate the leads from each other and protect the connections.

Finally, put a dab of heat sink paste to the back side of the LM7806 and attach it to the heat sink with a screw.

When connecting them, select the appropriate connectors for your application. In the photo below, the red lead is connected to a switched 12V source (usually your ignition), the white lead is connected to the positive post on a gauge, and the black lead is connected to a ground.

Finally, attach your harness and reinstall your gauges!


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