Re: AC/DC power supply

Joe Zeglinski

Thanks for the suggestion Joe M.

However, if I clip off one turn of the spring, it will now be a bit shorter - so I might stretch it to push the centre pin to his original home position. I suspect that the spring tension will not be significantly changed by a single cut, and there aren't a lot of turns in the coil.

Then again, if we can consider each turn as a separate spring, and the turns added in series, the new spring tension will not be the sum of the tension of each turn, but the product of tensions (spring constants), divided by the sums (as in calculating capacitors in parallel). This means that just removing one turn of the spring may not significantly reduce the tension of say a 5 or 6 turn spring - as I recall is used in the fused plug version.
To make a significant change in the stiff spring you really need to change the mass of the wire, while keeping the length the same. Otherwise you will have a loose centre, without much change in tension.

I am going to have to think about and experiment with this.

Joe Z.

----- Original Message -----
From: "JoeMize" <jmize@...>
To: <ap-gto@...>
Sent: Tuesday, March 18, 2008 2:24 PM
Subject: Re: [ap-gto] AC/DC power supply

JoeZ, if going the rout of modifying the cigarette plug have you looked a
reducing the spring tension? When you reduce wire diameter resistance is
increased resulting in less current flow. Clipping off a turn of the spring
will lower its spring rate reducing the springs tendency of pushing the plug
out without increasing resistance. Just another thought...joe ;)

"May You Go Among The Imperishable Stars"
Joe Mize
Chiefland Astronomy Village, Fla.
----- Original Message -----
From: "Joseph Zeglinski" <J.Zeglinski@...>
To: <ap-gto@...>
Sent: Tuesday, March 18, 2008 2:34 AM
Subject: Re: [ap-gto] AC/DC power supply

Hi Joe M.

I will agree with you on your statement that cigarette lighter plugs
tend to want to gradually walk out of their socket.
In fact, I purchased a RoadPro 12v Hair Drier and tried to plug it into
of the two auxiliary sockets on their RoadPro battery voltmeters. No way
would stay in place - it was totally unusable. In fact, it required a
significant amount of force just to push the centre pin down into the plug
by hand!

To answer the challenge I went through a bin of similar corded plugs at
an electronics store, and each one seemed different, but none were what I
would call satisfactory. That got me to investigating the cause of the
not seating firmly, so I took the end cap off the plug on the RoadPro hair
dryer and quickly discovered the problem with ALL such corded cigarette
lighter plugs - a THICK power cord is solder to the terminals, inside a
small compartment. When you try to push the pin inward, the power cord has
no room to scrunch down - resulting in an inordinate "back pressure" - so
will not stay set, and easily backs out. At that point, even if the plug
looks to be inserted, the tip is barely touching the battery socket centre
pin - a breeze would disconnect power!

I quickly realized a very simple quick solution, which I am going to
implement as a retrofit on ALL my cigarette lighter plugs.

(1) Remove the plug tip, and pull it out of the body along with the power
(2) Unsolder the centre pin wire
(3) Cut off about 2 inches (but still above the other, side springs
wire joint)
(4) Replace the cut off section with a "short bundle" of several much
thinner gage, TEFLON coated, "stranded" wires
(5) Put a heat shrink around the multi soldered joint, to prevent shorting
the new bundle to the other (negative) terminal
(6) Solder the other end of the bundle of Teflon coated stranded wires to
the centre pin

Now, when you insert the plug into a lighter socket, the 2 inch bundle
of thinner wire will easily push down, and "individually fan out" inside
body of the plug, and the bundle will carry as much current as the
single "lamp cord" wire section did. The Teflon coating will also not melt
from possible high currents - although with enough parallel wires, there
should be no more heating than the original thick wire. Finally, using a
reasonably smaller gage stranded wire, adds to it's flexibility.

This modification should make the plug totally unaffected by the
cable" being jammed inside, and the pin will have a much softer
The plug will not have any tendency to walk out.

I wish this is the way that all cigarette lighter cords were assembled,
but I guess the extra step of soldering a "compressible bundle" of smaller
Teflon wires, adds a penny to the assembly costs in China.

Hope this idea helps,
Joe Z.

----- Original Message -----
From: "JoeMize" <jmize@...>
To: <ap-gto@...>
Sent: Monday, March 17, 2008 10:51 AM
Subject: Re: [ap-gto] AC/DC power supply

r1300s, a 'different' Joe here.

I never use cigarette plugs. I learned a long time ago Cigarette plugs
back out by themselves for no reason at the most inopportune time. One
your three may have partially backed out, or one of the Dew strips is
causing over heating. I use banana plugs on the Pyramid binding posts


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