Technical 6 Volt Gauge in a 12 Volt Vehicle? It could be easier than you think! Cheap Voltage Reducer.

Hello! Welcome to a tech short from Mart's Garage (Sparks Division).
In this video I show a novel, readily available and most importantly cheap solution for 6v gauges in a 12V car. The parts are easily available anywhere in the world, and require minimal mods.
Check the video to see what the heck Mart's going on about now.
This will work in any 12V negative ground vehicle.
Mart.

 

why not an LM7806 voltage regulator?

 

Or the single voltage reducer Ford used for their gauge clusters for 20 years.

 

That one looks quite small, simple but rugged- and when you notice that the price is for 10 of them, pretty cheap. Can you do a wiring diagram to show how to adapt it to instrument use?
I learned about that Ford instrument voltage regulator when I was about 19, was driving along in my OT 69 Mach1, glanced at the oil pressure guage and it was pegged on zero- WTF??? Then I noticed that all the guages were pegged as if the key was off. Those instruments are on a big printed circuit, and the regulator plugged in the back

 

It's a pretty simple device,

Pin 1 - 12v input
Pin 2 - Ground (this is also connected to the metal mounting tab)
Pin 3 - 6v output.

But it will only handle about one amp of current. And it's a good idea to mount it to a metal surface, using the mounting tab screw hole, this provides a way for it to get rid of heat.

 

Exactly - I used a 7806 in my F1, cost less than $1, seen them 5 for a dollar in fact - one part provides 6v to all original gauges that need it - bolted to a clean metal spot on the under lip of the dash for a heat sink, next to the gauges - BTW, I measured the current the oil, temp, and fuel gauges use for full scale, about 225ma each, so the 1 amp 7806 properly heat sinked the metal dash handles all three gauges just fine

 

Excellent.

 

https://www.amazon.com/L7806-LM7806...child=1&keywords=LM7806&qid=1628605425&sr=8-6

 

Quite In-genius an idea. It uses a switchmode regulator chip and a mosfet, so it can handle a lot of current, probably more than the 7806. Being a switchmode regulator, it is much more efficient than the 7806, and does not heat up like the 7806. And getting to the Furd regulator, well it is probably the crudest regulator out there. Just a bimetal strip that cycles much like a turn signal flasher, only faster.
Only issue is that it won't work on positive grounded vehicles. But there is a solution to that.

 

Hello.
I'm not trying to say the USB thing is the only way to do it. We all have our own favourite way.
The Ford voltage regulators switch on and off and can only be used with a gauge that is very slow to react. If it is undamped like the one I am showing, it cannot be used with that type of regulator.
I've made voltage regulators using the LM7806 devices and I can tell you it is not easy to attach the wires in a robust way, and provide a heat sink. My viewpoint, was that having done the LM7806 method before, I would try something new. And in my opinion, it was far easier. Obviously, your opinions may differ and that is what makes the world go around.
Thanks for the feedback though fellas.
I never heard anyone mention using the USB devices before so I thought I would give it a try. For me the benefit was them being cheap, universally available and the mod to the lead is very easy to do.
Mart.

 

Yup, why use one part, when several will do the same job?

 

I used the 7806 in my 49 Buick to keep the stock gauges and run on 12 volts. Easy to assemble and works great.

 

Enjoyed one's way of getting his things working in his world but not so much the beat down.

 

Because that would be too easy.

Also why use a $2 part when you can spend hours modifying a $20 part

 

About the 7806, a 7807 may be a better option some times, as 7V is closer to normal running voltage in a 6V system.
Also, there's a series of 79** regulators too, suitable for positive earth systems, they regulate on the "negative line".

 

When using the 7806 do you need one for each gauge ?

and mounting it on clean bare steel with thermal paste in between will help with heat dissipation

 

Using the phone charger thingy lol s just a different way to skin a cat !!
It works and is simpler to wire up for the electrically challenged amongst us.

 

They can usually hadle 1.5A max each, depending on version. You'd have to check how much current each gauge needs.

As for cooling, remember that the cooling tab is electrically connected to the regulator, as is very common with electronics. For once it seems to be connected to pin 2 = ground so if whatever used for cooling touches other ground it shouldn't be a problem, other times keeping the component insulated from the cooling fin, or the cooling fin insulated from the surroundings can be very important.

If you use the maximum 1.5A and feed the 7806 14V as you usually have in a 12V system with engine running you'll have 14-6= 8 volts over the regulator, and at 1.5A 8V means the 7806 will cause 8*1.5= 12 watts of heat. That requires a pretty good cooling fin. The one in the picture (grabbed at random just for an example of the principle) is 50x45x50mm, its rated at 5°C/W, meaning that the fin temperature will rise 5°C for every watt fed into it, so 12*5°= 60°C increase above ambient. Could put the fin itself at 90°C on a hot summer day (without considering the extra temperature you get inside a closed car in the sun).

[Edit: picture didn't work. Imagine a 50x45x50mm aluminum cooling fin instead.]

That's just the temperature on the fin. There's a thermal resistance inside the regulator itself, and on the datasheet I found first that happens to be 5°C/W too. That means that the actual working chip inside the regulator also will be 5°C hotter than the cooling fin for every watt. So if the fin is 90°C and the regulator is 60 degrees over that that's 15o°C at the chip. The working temperature of the version I found datasheet for is 0 to +125°C, so at 150 the internal thermal protection will have shut it down long ago.

That's the long way of saying that even if a single 7806 can handle multiple gauges, it may be simpler (and cheaper, cooling fins are expensive) to use one regulator for each. At low enough load it can work without a cooling fin at all, and if the load is kept sensible it can manage fine with a very basic fin, i.e. a piece of sheet metal -preferably copper or aluminum.

 

The 7806 is so cheap and easy to build I used one for each gauge in my 49 Buick.

 

Here’s what I like about it. If you’ve lived in the modern world the past 20

years or so, you probably have a few of those under your seat, in the console, etc of your DD.
Easy and on hand to repurpose.

 

I used an LM7805 with a power transistor so it could handle around 6 amps, stuck it in a little diecast box with a heatsink & a tiny 12 volt computer fan, and use this to run any other 6 volt things which are too fiddly to convert to 12 volts (heater fan, etc.). This unit is connected to the ignition circuit, so is only "on" while driving. You could connect it to the battery via a switch if you wanted to listen to your 6volt radio at the drive in, if you like. If you need more current capacity you can use a higher rated transistor.