The Stovebolt Site Forums The Shop Area The Electrical Bay Made my own "Runtz" style 6v regulator

I am converting my '52 to 12v electrical system to be able to run A/C, modern (vintage looking) radio, PA system, sub, etc. So, I needed to take the voltage from 12 to 6 for the fuel gauge and did not want to use a resistor. I don't like the cost of the commercially available "Runtz" regulators, so I built my own. I simply purchased a 6v IC regulator, mounted it on a piece of aluminum (acts as a heat sink) and mounted it behind the dash on the steering column/dash brace. Here is the finished product. Cost me about $5

I'm not good on electronics so I buy what I need. Hope your style "Runtz" works out well. Let us know.

And David, what is the number of the voltage regulator that you used? And doesn't it need more circuitry?
Denny G

I don't know the part number. But, it is a simple 6V regulator (7806) that can handle voltages ranging on either side of 12v. No, the regulators only need an input voltage and ground to work properly. These type of voltage regulator are commonly used on all sorts of electronic devices to step down and clean up input voltages. I have used them many times on all sorts of electronic projects. The by product of the voltage reduction is heat and that is why I mounted it on an aluminum flat bar (1/8" thick by 1/2" wide by about 2" long).

So, one red wire is input (left when regulator terminals facing down), one red wire is 6v output (right) and black wire is ground (center).

using a regulator will keep the output rock steady at 6 volts regardless of what happens to the input voltage. The result being a steady fuel gauge needle (other than the sender float moving up and down...which I would love to dampen out...hmmm).

Take a look at this photo of a "Runtz" style voltage regulator and you can begin to see it is exactly what I fabricated. The "hole" is the output terminal, the screw lug is the input terminal and the black wire is the ground. The regulator is under the blue heat shrink tubing. There might be a capacitor (filter) or two hiding under the tubing as well. Debatable whether or not a cap is needed. If the power output fluctuates, I will add a cap between input and ground and possibly even output and ground as well. But, I don't think caps will be needed (remember, old fuel electric gauge technology...not a modern sensitive electronic gauge).

Denny, What is an iC resistor and how would it be wired to the gas gage. I have this same situation on my 35 Pontiac project. The PO put a 12V alternator and battery in it. I am a duma$$ with electricity. I assume the black wire is ground but how about the other 2 wires?
Red to gage? and remaining wire where?


Weeds

IC is short for integrated circuit. If you want to know what is inside that black plastic cover you can look up the circuit by the part number. But that won't help much unless you have some education in circuit theory. But for just us few that want to know...the inside is a solid bit of material with some chemistry differences at very specific locations that change how the material reacts to current. They grow this stuff. No parts in there at all. Now that we all are clear on what is in there...:). There is an "op-amp" and some bias resisters that make it work. OP-Amp? Short for Operational Amplifier. The difference in the one part number to the other one posted by Denny Graham is the material and it's ability to conduct current. Higher rating means more current. lower rating means less. So, for the fuel gauge you don't need much. For the heater? Well that will take a lot more. And a radio? 6 volt has a "vibrator" and tubes to heat. That will take as much as heater. "Vibrator"? That is how to make radio frequency A.C. from D.C. voltage.
Weeds: Black is ground. One Red is 12 volt in. And the other is 6 volt out. Should be clearly marked.
Are we having fun yet? Enjoy.

What do the capacitors do in this circuit?

I stand corrected. Thanks Denny!
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&docid=FixwZ_GcwBRWwM&tbnid=LV0QyMuD62UccM:&ved=0CAUQjRw&url=http%3A%2F%2Fcr4.globalspec.com%2Fthread%2F12407%2FWhat-is-inside-Lm7805&ei=h4nwUpqMEITjoATJ2ILwBA&bvm=bv.60444564,d.cGU&psig=AFQjCNFTb8f8mwMbOStS3GAyisFMThwxdw&ust=1391581848796904
If you must know what is in there...:)
Ratings are from 750 ma to 1.5 amp. See I had to look it up. Keeping me honest, nice work. And if you must run more power you can get 11 amps from this one.
http://www.powerstream.com/dc-buck-boost.htm
For a small fee of course. In the world of IC power costs go up fast with current. But, for most things we might want to run... and the costs I would stick to the Radio Shack part.

Ok guys. In my opinion, this "design" is getting too complicated. remember, we are trying to reduce the power supplied to a very unsophisticated electrical fuel gauge. As such, you don't need to clean up the power on the input or output side. The gauge wont care. The way I see it, the only reason you might have to put a capacitor on the output side is if the regulator oscillates to the point of not providing power at all (rapid on/off switching). But, many/most of the modern regulator don't require the capacitor (the 7806 family is typical of this).

Many of folks have used the 7806 regulator with good results even if the voltage is slightly less than a fully charged battery (not counting resistance losses in the normally less than ideal circuitry).

True David, I thought early on that we established that
the stand alone LM7806 was what the simple Runtz devices
were.
I tried to take the use of it a little further for those that
might want to use an LM78xx series voltage regulator in a
circuit to handle 10 amps and not want to spend $150 on one.
This, like most discussions we have on the Stovebolt often
evolve into what is to complicated a project for some.
Sorry I didn't mean to steal your thread so I've pulled my
response as to not clutter up your original intent, which was
to tell how you made your own Runtz style 6v regulator.

Denny Graham
Sandwich, IL

The only reason for a "Runtz" is stable volts for the fuel gauge. There would be no reason to use anything more complicated than a drop resister for anything else in the electrical system. And the LM7806 works well and is cheap. I was just attempting to give a fun nit of information about what the "Runtz" is. Never meant to hijack the thread. My apology.

Got it, no problem Denny.

Steve: The voltage regulator will still do a better job at stabilizing the (output) voltage than a resistor, in my opinion. Again, no apologies necessary as all discussion is good and I failed to realize the thread took a different route as I was focused on the original topic.

I'm throwing this in for the guys like me that still have the positive ground 6 volt system. This same setup will work for the positive ground system by using the LM7905 regulator. It is a Negative 5 volt regulator. I am using the NTE961(same thing).
I ran into problems when I no longer could use my King-Seeley type of sensors on my Lincoln Zephyr. In switching to a variable resistance gas sender, oil pressure sensor, etc., I found them to be voltage sensitive. Hence the regulators.
One thing that David or anyone didn't say in how the regulator is mounted to the alum. heat sink. On the 961 the metal screw tab is connected electrically to V(in). So it must be isolated from the alum. heat sink or bad things will happen if one mounts the heat sink to ground. Not sure about the LM7905. I also use a 1 amp blocking diode on the input in case someone hooks the battery or jumper cables wrong. This can easily happen on a positive ground car where both cables are black ( as original).

I mounted the regulator directly to the aluminum (heat sink) with paste between. Nothing in the regulator literature suggests that the regulator case/body cannot be grounded.

David, on the device I'm using I noticed on the packaging that V(in) was written at both the center pin and at the top next to the screw terminal. Using an ohm meter I confirmed they were in common. The package included a clear plastic insulator for the back side and a plastic isolation spacer for the screw. Also, the thermal conductive paste is always a good idea.
Again, unsure if all this is needed for the positive regulator.

The regulator I purchased also came with the parts mentioned above. However I confirmed the the case of the regulator is not tied to either V in or out. So, whatever regulator is used, you must take note of circuiting diagram on packaging. Some regulators have ground on left rather than center, etc.