CPVC Fun!

[Silver Dollar]

I've been playing around with some PVC pipe to make a waterproof housing for
a PI coil. The CPVC is thinner walled and you can get 1/2" pipe that's 5/8" OD.

First I tried bending a half round coil. One side came out good but the other
is a little shaky. I didn't bend the flat side first too so now I'm not sure how to
proceed.



I was trying to make something like this;



Well then I got an idea to make a stop sign shaped coil;

Here are the parts;


Here's the general idea;


And the assembled housing;


I'm not sure how hard it will be to get the wire inside or if it's too big
for the shaft to support it. I could put another T on the other side. But
it's fun playing around and building things!

[DOOLEY]

hello silver dollar,

I made a coil very similar a few years ago,
didn't use all them joiners though.

I used "polly plumb" pipe,
or "barrier pipe",
modern day plastic central heating pipe.

anyways,
warm it up with heat gun and bend it,
it resists kinking very well,
allow it to cool whilst being held in the shape you want.
or run it under a cold tap.
it will retain that shape when cold.

next I "honed out" the T piece for the handle so that it will
slide over your formed pipe out of the way.
I then used pvc covered 0.6mm solid hook up wire for my coil,
thread the first loop through,
then,
tape it to itself leaving yourself about a 2" gap in you heating pipe to work with.
then simple rotate the whole bundle to the required amount of turns.

tape it all up tight, leaving your ends to connect to long enough to come out of
the T piece.
then wrap with personal choice of material for shield,
( personal choice is tinfoil shield from striped down sat coax )
then one more coat of tight tape,
close and glue her up,
connect coax,
then.........

squirt shot of expanding foam in to stop coils moving in the pipe.
otherwise, eventually, wire will brake.

have fun.

[Davor]

I bought a tin of PVC glue at final sale when a DIY shop went bust, and it was expensive even at bargain price. I might give it a go. My idea of inserting a coil was to use a CAT5 cable and rewire everything outside the loop.

[Silver Dollar]

Thanks for the tips Dooley! You wound the foil and tape on the coil in the 2" gap?
I took a degaussing coil out of a TV recently and it had some thick plastic backed
foil shielding it and the ground wire taped to it. I could try wrapping that on this
coil. I hadn't thought of shielding it....

I decided it would be easy to wind if I kept it in two halfs. I tapered the inside
of the pipes to let the wire run smooth. I didn't think of taping the wire to itself
and then rotate it. Brilliant!

I shrank it down a bit. It was 13" side to side and 14" point to point now it's
11" side to side and 12" point to point. I also put a cross piece so it will balance
better. I figure glue the parts on 2 halves, wind the wire, run the wire to the middle
then glue the halves together. Here's a picture;


By the way it cost $8 for all the parts including 10 feet of pipe! (I already had the glue).

I thought of using centronics printer cable. It has 25 wires. You could run it through the pipe
and wire it together at the T then slide the T over the wires to seal. (one of the T's is routed out)

Centronics Cable;


Thicker cable and coil;

[Silver Dollar]

Darn my glue has turned to jelly (I hope yours is OK Davor!). It uses MEK as a solvent
so I tried adding some more to melt it but it doesn't look good. It's just sitting on the top.
I guess I'll have to buy some more when we are out apple picking tomorrow. It's only
$3.50 a can around here.

I took 2 wires off that 25 wire cable and it came down to 330 uh and 3.5 ohms (28 Gauge).
It fits perfectly in the pipe and is shielded to boot! So I'll probably use that. I had hoped to
glue the sides together today but I'll have to wait....

[DOOLEY]

Doh,
I forgot to mention about wrapping a bare drain wire on top of
Shield before last layer of tape.

But yes,
All done in A 2" gap,
Actually quite easy when you get going,
First few winds of coil is the hardest,
Gets easier after that.

Took about 1/2 hour to do coil and first wrap of tape,
Another 1/2 hour just to do shield,
But end up with a tidy coil in water proof
Housing.


Took about

[Davor]

Darn my glue has turned to jelly (I hope yours is OK Davor!). It uses MEK as a solvent
so I tried adding some more to melt it but it doesn't look good. It's just sitting on the top.
I guess I'll have to buy some more when we are out apple picking tomorrow. It's only
$3.50 a can around here.

I took 2 wires off that 25 wire cable and it came down to 330 uh and 3.5 ohms (28 Gauge).
It fits perfectly in the pipe and is shielded to boot! So I'll probably use that. I had hoped to
glue the sides together today but I'll have to wait....

You need 25 turns of tightly packed wire with a smaller diameter, so no wonder you ended up with 500uH.

Beside the CAT5 cable that is already shielded, I thought of using a ribbon cable to get a faster coil. Inter-winding capacitances should be much smaller that way, because a single turn sees only two other turns that are preceding and following, and by virtue of self-transformation these have much smaller influence on self-resonance. Just like with a spiral coil. I thought of rolling it longitudinally together with some insulator, chocolate filled pancake style, and stuff it all into a tinned braid of a coax (RG8 or similar) as a shield.
Wiring should be easy enough by virtue of wire position - just shift the wires of one end one wire further than the other, and solder it one go.
A single turn of such "cable" should do, and it should be pretty darn fast.
I expect 5ohm or so resistance.

[Silver Dollar]

I found some 25 conductor ribbon cable the other day and thought the same. I figured you would
need a big form to wind it on though. I've seen it used as shielding by Eric Foster.

[baum7154]

You need 25 turns of tightly packed wire with a smaller diameter, so no wonder you ended up with 500uH.

I thought of rolling it longitudinally together with some insulator, chocolate filled pancake style, and stuff it all into a tinned braid of a coax (RG8 or similar) as a shield.
Wiring should be easy enough by virtue of wire position - just shift the wires of one end one wire further than the other, and solder it one go.
A single turn of such "cable" should do, and it should be pretty darn fast.
I expect 5ohm or so resistance.

------------------------------------------------

Regarding rolling it longitudinally around some insulator may I suggest that you look at the polyethylene foam 'Backer Rod' used in concrete crack repairs? It comes in diameters from 3/8" to 1" diameter, comes in 15 foot lengths or so, it is very light, resilient, and a good dielectric. It seems to me that it would make a great core for your ribbon wire coil.
In the US it can be found at hardware stores and lumber yards.
Just a thought.

Dan

[Davor]

Using a ribbon cable as a shield for a ribbon cable could work fine. I like the approach already. Less fuss than stripping a coax.

I'm not considering rolling a ribbon cable on a form, but placing some insulator to keep distance, and roll them together just like a chocolate filled crêpe,



This insulator layer would take care that distributed capacitance is seen only among the adjacent windings.
I might use some form to roll it over, but I don't have to.

[Silver Dollar]

So here's the 9 inch a little further along;


And the octagon;

[Silver Dollar]

Wiring Picture;


All wired;


And my growing collection of CPCV coils;


It's fun to play with this stuff, it's cheap and easy to work with.

It's tough to make smooth bends and you have to plan how to wind the
coil and shield it then glue it together. I used IEEE 1284 centronics parallel
cable. It has 34 wires as 17 twisted pairs and a shield. Tricky to solder though
as it has PVC outer layer. It melts and runs with applied heat!

Now to figure out how to run the coax to the coil....

[Silver Dollar]

I decided to make the big oval into a PHI

Φ (greek character)

.

The final size is 7 1/2" x 11" which is somewhere close to a 9" circle. It's cute!

[Silver Dollar]

Here's the little loop, I reformed it into a mini;

[walkman]

Silver Dollar, very nice works.