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!



Each voltage reducer cost about $3 and I learned a bit about how gauges and reducers work. Please don't hesitate to post questions and comments and I'll do my best to respond.

-Stefan

 

Very cool. Off to the "Electronic Connection" tomorrow. Cool Post. Thanks.

 

That's badass man!...sure, it kind of sucks to have to make one for each gauge, but it's definately worth it to keep the stock gauges safely...my question is, does it allow you to use the stock Amp gauge safely?...I've got a bunch of 6v Stewart Warner gauges that I'm saving for a 40's style project, and being able to use 12v for the starter and such while using my 6v gauges without costing an arm and a leg is a hell of a good deal to me...

 

Hey there, Ruiner. Amp gauges are a totally different story. They actually measure the current flow from the battery. Voltage regulators maintain a specific voltage by altering their resistance in response to changes in current.

In theory, you should be able to run your amp gauge as is. In practice, many people convert them to volt meters.

 

Amp gauge doesn't care if it's six or twelve volts.

type too slow, 49 custom beat me!

 

In general, your ammeter doesn't care what the voltage is.

 

That is an awesome idea for saving those 6 volt guages!!! Thanks for sharing that info! Good job!

 

Yep...I use a short piece of 1" square tubing. Plenty of surface area plus air flow path.

 

very nice post.
like it a lot,gona be useful

 

Great post, will come in handy very soon.
Thanks

 

Handy and saved. Thanks!

 

Thanks alot for the info. Nice info for us.

And having to use a ground actually makes this a better unit than the ones that you see that are inline w/ no ground.

10 of them for $4. http://cgi.ebay.com/NEW-10-x--L7806...temQQimsxZ20100128?IMSfp=TL100128196002r26359

 

Where do you get those parts, like a radio shack or something?

 

Pickup 10 of the 7806 for $4, free shipping on my link above.

 

The 7805 is a 12V to 5V regulator, while the 7806 is 12V to 6V. As 440 mentioned, it probably would be ok, but I suspect the gauges might read a little on the "low" side; even original 6V batteries didn't always put out 6V. The capacitors can be anything between 0.1 and 10ų as they are just to reduce noise.

 

You can probably get away with using more than one gauge on an LM7806 circuit, as they are rated for 1.5A. There are more parts involved (thus bumping the price), but an adjustable LM 317T regulator could be used as well. The 317 is also rated for 1.5A.

I have often wondered why this wasn't discussed more often around here.

Tim D.

 

Lurkin and saved! Great info that will be used shortly. Thanks

 

For 5A there is a 5Volt version availible...i just forgot the number.
78L05 or something.
And if you put a diode(is that english , too) on the middle pin(connectet to ground)
then you end up with 5.7 Volts as the diode "eats" 0.7 Volts.

That way you need only one for all.
Michael

 

Much thanks for that great info!

 

Excellent tech - cheers!

 

thanks alot! fo you have any ideas for a 6 volt heater motor, or say a 6 volt horn? i m going to need both. -andrew

 

Run your 6V horn on 12V....it's nice and loud! Don't run a 12V horn relay though, stick with the 6V relay. The 12V ones often can't handle the increased current.




I've done several of these conversions and never used the capacitors. And while it may make a more technically correct power supply for small electronic projects, personally, I don't think they're required in this type of circuit. Any "noise" that made it through the IC will be largely irrelevant to the bimetallic strips in the gauge circuits...they don't react quickly at all.

 

Excellent thread! I've got a great SW 6v Tach that I wanted to use....now I can! Any thoughts on 12v into a 6v wiper motor....rains alot in Paradise!
Aloha!

 

I can definitely testify for the increased volume of 6V horns on 12V! And you are absolutely right that the capacitors are not required for old electric gauges; its a hard habit for me to break, plus at about $0.10 a piece, it was hard not to use them.

There was a question above about heaters and wiper motors: a high load ceramic resistor is more appropriate for those. I've seen a few threads that provide more details.

 

Thanx 49 Custom...great info and appreciate the sharing for sure...I've always said, "Nobody's born knowing this stuff !"

 

Thanks for the info.Gona need it soon!!

 

very nice.....

 

Thanks for this.

 

Move this to the tech forem?

 

Great info thanks