WTD 6 VDC Pos Ground to 12 VDC Negative ground Convertor or Schem.

[Rob K2CU]

Add a small 12 V Alternator and separate 12V battery to power any toys.

[KM1H]

If you want to discuss cars and older automotive stuff, you are right in my comfort zone. Feel free to bring it on. We can do it by email and not snarl up this forum.

Email is a waste of time. Either OTA but Ive no idea what your call is or are you coming to Nearfest?

[The Slab Bacon]

If you want to discuss cars and older automotive stuff, you are right in my comfort zone. Feel free to bring it on. We can do it by email and not snarl up this forum.

Email is a waste of time. Either OTA but Ive no idea what your call is or are you coming to Nearfest?

Come on Carl just about everyone here knows my call. You obviously dont read all of threads here. My call is KB3AHE. I want to get to Nearfest but I just cant seem to make it happen. I'm usually on on Friday and Saturday evenings for the WFDN at 5:00 PM, but can be talked into other times if necessary.

But, better than that.................. 410-668-0437 any evening between 6:00 and 9:00 PM

[W7TFO]

While Carl & Frank are off to parts unknown to joust with vertical antenna sections...

Perhaps the easiest, non-invasive way to get what you want is to take a boat battery box, glue a solar charger on top of it, put a good battery like an Optima yellow top inside, and set the whole thing in the bed and run your radios off it.

No mods to your pride ride, ought to last for years.

73DG

[Carl WA1KPD]

All I want to do is run a GPS and cell phone charger.

You would think I want to install a pair of 813s modulated by a pair of 813s and rebuild the entire electrical system. using a small thermo nuclear device:o

It just occurred to me the iPhone and the Tom Tom probably use 5 V as the end voltage. I wonder if I could rig up a LM317 and get 5V neg ground from the 6 v pos ground DC to run it? Everything will be plastic and isolated anyway. I'll have to look at the specs and see.

Carl
/KPD

[KB2WIG]

A small windmill under the car along with one of them bicycle generators would jump up the voltage. Spam egg sausage and spam. You don't have to rewire the car that way. Maybee even hide a small batt underneath.

klc

[Opcom]

All I want to do is run a GPS and cell phone charger.

You would think I want to install a pair of 813s modulated by a pair of 813s and rebuild the entire electrical system. using a small thermo nuclear device:o

It just occurred to me the iPhone and the Tom Tom probably use 5 V as the end voltage. I wonder if I could rig up a LM317 and get 5V neg ground from the 6 v pos ground DC to run it? Everything will be plastic and isolated anyway. I'll have to look at the specs and see.

Carl
/KPD

No, you need a LDO or low droput regulator. LM317 can't make 5V from 6, but maybe from 7 or 8.

L4940V5 only needs about 0.45V more on the input than the output so will make 5V from 6V.

A TO-220 regulator made by STMicroelectronics, avail from digikey.com

[The Slab Bacon]

Normal "working voltage" for a 6v vehicle electrical system is around 6.5-7.1v in the real world with the engine running, and 6.3 with the engine off. That will prolly just work for a 7805.

Be sure to keep everuthing insulated / isolated from ground.

(or just change the polarity of the vehicles electrical system it's a 5-minute job)

[KM1H]

The real world is that generators often dont start charging until 800+ engine rpm and 5.9-6.0V is rather common when off and its a cold day. The generator charging current is determined by its rpm and starts low of course. Also since the battery is in discharge with a heavy load at idle less than 6V is possible. OT's can remember the headlights dimming coming to a stop and the heater motor slowing down. Keen ears could hear the radio vibrator slow down.
There were some low drop in sytems available for public safety, ambulances, busses, etc that kicked in as low as 500-600rpm using different pulleys and electrical components.

Standard flathead Ford regulators were set at 6.7 volts to engage and 7.3V for the voltage relay to cut out. Other brands were similar.

[KM1H]

Come on Carl just about everyone here knows my call. You obviously dont read all of threads here. My call is KB3AHE

I certainly dont, those long winded 2x3 calls are hard to remember anyway. I only read threads that interest me as life is to short to spend all day on the PC.

I guess your name is Frank after reading someone elses reply. I have GFZ down as Frank and 2 is too hard to remember Maybe you should use Frank3 based on your call district. Now there are 2 Carls in this thread from the first district but Im older and better looking so the other one can be Carl1A

After all that I need some fresh air....carry on.

[Carl WA1KPD]

No, you need a LDO or low droput regulator. LM317 can't make 5V from 6, but maybe from 7 or 8.

L4940V5 only needs about 0.45V more on the input than the output so will make 5V from 6V.

A TO-220 regulator made by STMicroelectronics, avail from digikey.com

Opcom,

Thank you for the idea, like the LM317 it carries a common ground, but I am thinking that won't matter since neither item will be referencing to the vehicle ground. I just need a small piece of perf board, a input cable and cigarette lighter (wired backwards) and then a plastic case to hold the perf board and two female cigarette adapters.

Comments on the circuit idea and logic are welcome .


73

Carl

/KPD

[The Slab Bacon]

I certainly dont, those long winded 2x3 calls are hard to remember anyway. I only read threads that interest me as life is to short to spend all day on the PC.

Yea, right............   You dont miss a trick and always like to get the last word in if others will let you. I also have all day seeing that I sit in front of a computer all day at work.

nothing like a good slack every now and then........................  

[The Slab Bacon]

Comments on the circuit idea and logic are welcome .

Carl, I dont know about that device Patrick was talking about, but a 7900 series regulator is a negative lead regulator in a TO-220 case so you could just ground the mounting tab and hook one lead to the vehicles electric system and one lead would be the outpoot to whatever you want to run. IIRC, a 7905 would be a 5v negative lead regulator.

2 Carls here could make things a bit confusing................................  

[Carl WA1KPD]

Frank- and others

Here is what I am thinking about. Imagine a small hard plastic case with a set of wires coming out of it attached to a male cigarette plug. Inside the magic plastic box is the regulator, heat sink and other needed components.  Mounted on the box is either two female cigarette lighter sockets or USB sockets. the entire box has no external conductivity. When I want my 5 v I just plug the cigarette lighter plug into the +6V ground lighter jack on the dashboard, and my other plugs, or USB ports for 5V neg ground. Simplified drawing would be like this. I can't see why it will not work.
Thanks and 73
Carl
/KPD

[Opcom]

I agree no need to ground anything there.

Yes that circuit will work

The 6V discussion/hubub is why I suggested a very low drop regulator. A VLDO is just the best part for the job. The 1.5A part I mentioned will do a better job at regulating a 500mA typical USB charging current (dropout 0.25v@500mA @50 deg C.) if the input voltage is low-ish, than a 7805 or LM317 will, because those old favorites have higher dropout voltages of 1.7V (L7805, the low dropout version) and 1.75V, respectively at 500mA and 50 deg C. The datasheets will show that, so you be the judge of it. If you foresee the current being high enough to cause dropout issues, a regulator for each USB socket would help.

L4940 - input cap should be monolithic or ceramic, output can be electrolytic.
L78L05 - low ESR caps, tant. mylar or other - output can be electrolytic
LM317 -  low ESR caps, tant. mylar or other - output can be electrolytic

Modern regulators are sensitive due to improvements. Because there's no real ground, just a lot of wire, treat it like an RF IC and put the caps right at the IC.

Whichever regulator is chosen it is wise to add a transient supressor or a zener diode in front of it to eat any spikes that come from the electrical system such as when starting, load switching, etc.

Too bad Vin and Vout are so close together or a buck would work well. Maybe a buck-boost but the monolithic ICs are tiny and require reflow soldering these days.

Post up some pics of the plug, box, board, etc. when you make this. It will be good for others who have the same requirement!

[The Slab Bacon]

IIRC, LM317 is supposed to be an adjustable + lead reulator.
       7800 series is a fixed voltage + lead regulator and
       7900 series is a fixed voltage - lead regulator.

Using a 7900 series (7905) and grounding the mounting tab just makes things a little easier to build. (less to keep floating) uses the same circuit ou have drawn, but just reverse the polarity of the in and out leads. Also being able to ground the mounting tab makes it a little easier to heatsink. No worries if the heatsink touches anything metal.

I have also made regulators for "odd" voltages by floating the center pin and stacking diodes and/or zeners under it. It gives you a little "adjustment".......

[Carl WA1KPD]

a regulator for each USB socket would help.

Excellent idea. A real "duh" moment for me as I was worried a bit about the current of the two devices at the same time. I'm thinking of doing three. Two with USB and one with cigarette lighter.
I have a PC to cannibalize for the USBs and I think I will take a close look at the PS components.

Really appreciate the help

[Carl WA1KPD]

IIRC, LM317 is supposed to be an adjustable + lead reulator.
       7800 series is a fixed voltage + lead regulator and
       7900 series is a fixed voltage - lead regulator.

Using a 7900 series (7905) and grounding the mounting tab just makes things a little easier to build. (less to keep floating) uses the same circuit ou have drawn, but just reverse the polarity of the in and out leads. Also being able to ground the mounting tab makes it a little easier to heatsink. No worries if the heatsink touches anything metal.

I have also made regulators for "odd" voltages by floating the center pin and stacking diodes and/or zeners under it. It gives you a little "adjustment".......

Thank you Frank. I think I'll keep the sink inside the box and drill air holes. I want to keep any thought in the future of the heat sink being a ground reference for anything off the table!