tank circuit - what output do I need?

**maxcosity** · 05-31-2003, 05:48 PM

I'm building a tank circuit, but I don't know what the output amperage needs to be?

Also I am plugging the output of the tank circuit into this other circuit which regulates my 12v power source. What output amperage should that need?

Here is the tank circuit I'm building:

And here is the regulator I'm building:

(ill upload later)

What voltage and amperages do I need to make sure I have for the output. I have the 55w DC-DC PSU that comes with the Cubid cases.

Thanks,
Kevin

**Mp3Goose_Your King** · 06-01-2003, 12:37 AM

Umm the amperage will vary on your car based on what your running.

The voltage of the output of the tank circuit will be whatever your car is. What the tank circuit does is when you crank your car up and its running at like 14v the capacitor stores this voltage so the next time you crank it wont drop that low.

The ouptut of the regulator would be 12v, since it regulates the voltage.

**maxcosity** · 06-02-2003, 01:13 AM

Can I use both of these circuits -- in series to one another?

Also, where can I find some of this stuff.. I picked up some caps from Radio Shack but they didn't have the right diodes (I don't think), the semiconductor, or the bigger caps (22,000 or even half that).

**stimps** · 06-02-2003, 07:38 AM

I've got a untested but SURE to work idea, because its so simple. You need a large germanian diode. (dick smith stock it) and a small 4Ah SLA or something similiar. Hook up the cars positive power to the germanian diode, so it goes thru that, to the positive of the small 12volt battery. Then run your power feed to your DC to DC supply off that. When the car is off, the computer can draw power from the battery, and if it drops low enough, will draw power from the vehicles battery also. When the engine is running, more than enough voltage will come thru the diode and top up your SLA battery and run your PC. Then if you stop it, and crank the motor, the vehicle battery will drop to 10 or even less volts, but your dc to dc supply will still recieve 12 volts or so and not even notice the cranking.
Obviously, you ground your power supply to the car, and the sla battery also. The sla battery will be good enough to run your PC for 5 mintues or so, but i dont think you will ever crank your engine for that long!!

Like i said its untested, but ill test it soon. Its so simple it has to work:P

**maxcosity** · 06-02-2003, 10:48 AM

yes, please try that out and let us know what you find!

**dansoton** · 06-02-2003, 11:54 AM

Firstly can I appologise for being really ignorant and stupid about electronics but, in the diagrams above the positive terminal from the batteries are connected, but the negatives just goes to ground - surely this means the circuit is open and so won't work? Obviously it does work, but I just don't understand why...

Many Appologies in advance!

**maxcosity** · 06-02-2003, 02:23 PM

Originally posted by dansoton
Firstly can I appologise for being really ignorant and stupid about electronics but, in the diagrams above the positive terminal from the batteries are connected, but the negatives just goes to ground - surely this means the circuit is open and so won't work? Obviously it does work, but I just don't understand why...

Many Appologies in advance!

What's missing here, because this is VERY COMMONLY UNDERSTOOD in the automotive world, is that GRN is actually hooked up the the battery's (-) terminal.

In fact, on just about every car, the chassis (metal) is ground and it is hooked up to the (-) terminal on the battery. This allows you to shorten the length of your ground runs, saving wire and making it safer for electric components to be run in a car with sharp metal corners, etc..

So the circuits DO work, you just need to ground to the (-) on the battery (all cars are like this from the factory - don't worry about this).

**PTCruiser** · 06-02-2003, 03:43 PM

LT1084IT-12 is a low drop out linear regulator...

That mean to get 12 V regulated you need Vin >12V...

So it will not work engine stopped...

**maxcosity** · 06-02-2003, 04:30 PM

Originally posted by PTCruiser
LT1084IT-12 is a low drop out linear regulator...

That mean to get 12 V regulated you need Vin >12V...

So it will not work engine stopped...

Right which is why I said I would be plugging the 22000uf cap circuit (1st diagram) in and have the output into this tank circuit, therefore the "engine will never stop" (in other words, there will always be usable voltage coming out of the 22000uf cap while the engine cranks.

Although you do bring up an interesting point, that is, I wonder if this cap will supply 12v or if it will supply more. It's rated at 25v so perhaps it will just use 25v when it "discharges" into the tank circuit when the engine is cranking.