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Old January 5, 2017, 05:16 PM   #126
Reloadron
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Reloadron, what do you consider to be 12 volt with high current? With no effort I can burn wires up with 12 volts.

F. Guffey
What do I consider "high current"? I really don't know, maybe exceeding 20 amps. Really depends on the application. As to burning wires up? Depends on the wire gauge. Now is 20 Amps really high current? Nope, not really but it's all about a point of reference I guess. Heck, when cranking the engine to start I would guess my truck starter draws a few hundred amps at about 12 volts.

One quick note about dynamotors which have been mentioned before. When I was a kid growing up in the 50s I grew up in Brooklyn, NY. Canal St. in Lower Manhattan was the war surplus district with mountains of stuff from WW II and Korea. No shortage of dynamotors. My first ham rigs were ARC-5 Command radios.

I don't want to get off on tangents, while interesting motor generators the thread has no room for them.

When the wife and I return in February I will continue to experiment with induction heating and using induction heating to anneal brass. The brute power supply laying down at my sister's is a needed item.

I still haven't a clue how much power will be needed to anneal case necks in a nice time frame. I also want to look into turning the MOSFET gates On/Off using a timer. I would guess rather than power up and power down the entire unit that turning the gates on and off would be the way to go.

Ron
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Old January 5, 2017, 05:41 PM   #127
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Yes. Using an adjustable timer to drive a P-channel MOSFET power switch makes sense to me. Put the MOSFET in series with a Schottky diode with a high enough voltage rating to protect it from flyback, and you'll have a power switch fast enough to ensure the tank rings on startup the way it should. The timer then will be the heat control.
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Old January 5, 2017, 05:49 PM   #128
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That is my plan.

I did go down the basement rummaging and did find my old LCR bridge which actually works. The pictured coil with the roughly 2" ID is about 2.0 / 2.1 mH. I should be able to hit Lowes or Home Depot and get some 1/4" OD copper tube stock and wind another coil with a smaller ID.

I have several configurable octal base or 11 pin base timers. If the gate thinking works then I'll just make a simple one shot. Thanks for the reminder as to flyback diodes. Been awhile and this is well outside my former environment and comfort zone.

Thanks Nick
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Old January 5, 2017, 06:36 PM   #129
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Like you, I've got a dated B-K LCR meter sitting in the basement. You remind me it's been so long since I had it and a number of other meters and various pieces of equipment out, that I should double-check that I've pulled all their batteries. I should also take all the vacuum tube equipment and other line powered gear out and give it AC in gradual steps with a Variac to let the electrolytic capacitors re-form their oxide layers.

I'll bet the old single-layer cylindrical air core coil formula put into Excel will come close enough to give you a good design basis for your substitute coils. I'm sure you have it, but for others reading, it is:

μH = (nr)² / (9r + 10l)


Where
μH is inductance in microhenries
n is the number of turns
r is the mean radius of the coil (¼(ID + OD)) in inches
l is the length of the coil in inches

It is generally credited with about 1% accuracy, which is better than the capacitor tolerances are likely to be.
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Old January 5, 2017, 06:52 PM   #130
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Unclenick, thanks for the old formula. Should work in Excel I would think. Yeah, same deal, old test equipment with tubes. The batteries in a Simpson 269 were ugly and the 22.5 volt batteries are hard to find. I really don't even know why I have a Simpson 269? Had a few old Fluke DMMs and a 9V battery ate the whole connector. Someday I need a dumpster.

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Old January 5, 2017, 09:57 PM   #131
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Ok. I pulled the trigger on the dual psu and the 1000 w unit. I picked up a few ferrite o's and some 12ga solid copper. I also bought a small timer which I plan to power a relay with. I'm obviously leaps and bounds behind you guys but I will post my results when my stuff comes in anyways. Thank you all for the help.

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Old January 6, 2017, 06:43 AM   #132
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Kris, we are about the same level, experiment to find instead of work it out mathematically.
I've tried green, yellow, brown & red large diameter ferrite, between 1.5 & 2"
And I'm having the best luck with 'green' right now.
I'm going to try a variable resistor in the spot where a fixed resistor is now and see what that gets me.

At $16 per pair with infinante adjustment knobs included it's worth a try.
This is from a guy that works with cartridge brass annealing for a living, so I'm confident he's not sending me on a goose chase...

A source for 1/8" dead copper (about 8 or 10 ga wire diameter) without buying an entire roll is hanging on the shelf at auto parts stores,
Nice length for this stuff. It's pure dead copper tubing for higher pressur automotive gauges.

Here is something for the 'Ironic' files,
That copper tubing is a little hard, I used an annealer to soften the tubing for an annealer!
This is a little small diameter for the old 'Pack Sand' to keep the tubing from linking, so I filled it with water and froze it.

Tried the 'Hot Glue' thing thinking the first time the tube heated I would just use air and blow the glue out...
Copper takes the heat out of hot glue WAY to fast to ever get the tube full...
Thought about throwing it back in the annealer to keep it warm while filling, but switched to water since freezing it was about 20 minutes outside right now!
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Old January 6, 2017, 08:45 AM   #133
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Kris, just keep at it with your approach and don't hesitate to post any pictures, progress or even steps backwards. While I am pretty much stuck till I get the PSU I want up here I want to try and wind a smaller coil and maybe find a core and wind a C core. Thinking back if we look at The Annie Cartridge Induction Heater using the C form inductor it looks to have only a few turns on each leg. Also looking at the image it is difficult to tell if they are using a center tapped coil design? I can't make it out anyway.
Little by little we can all add to this thread with any progress or lessons learned.

Ron
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Old January 6, 2017, 09:03 AM   #134
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From what I can tell it looks like the annie c core coil is outside tapped with the crossover in the center. You can see it better from some of the YouTube videos.

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Old January 6, 2017, 09:17 AM   #135
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Yeah, the videos are more revealing and there are some quite good videos out there. On another note, as to power supplies, a solution I have seen used is if you can find an old microwave transformer and using dremel tool or hacksaw cut the secondary off the core. Using some #12 AWG start winding a new secondary. Rumor control was like 30 or 40 hand wound turns should yield about 12 to 24 volts give or take. Works out to be pretty inexpensive and now I wish I had gutted the transformer from the old microwave.

Ron
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Old January 6, 2017, 01:47 PM   #136
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I'm a pack rat with a recycle bin,
No microwave, TV, Computer monitor goes unmolested...
My first try at a case feeder was a microwave turntable motor.

And just for the record,
When I went from open coil to ferrite, 3 wraps on each side of the ferrite works just about right.
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Old January 6, 2017, 05:08 PM   #137
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You can disassemble and rewind about any old transformer. I've done that by calculation for special purposes, like winding double box shielded power transformers for super low leakage instrumentation power supply applications. In that case, though, because the shielding was going to eat up space, the core had to be oversize for the power it was handling, and that's why the calculations needed to go from scratch.

But you can avoid that if you find a standard E-core transformer that still works and that has the power rating you want. The secondary is usually the outer turns on the bobbin unless it has a split bobbin (in which case you cut away only the windings on the secondary half of the bobbin. You can then put your own secondary on it as Ron described.

I have an old 1500 V-A 1:1 isolation transformer that would be a good candidate for this kind of alteration. I would want the new secondary to put out about 1/10 the voltage at 10 times the current, so the new secondary magnet wire I selected would have 10 times the cross-sectional area of the original secondary winding wire and 1/10 the number of turns. It's pretty much that simple.
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Old January 13, 2017, 09:49 PM   #138
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So I have one psu up and running so I'm running the 1000watt unit on 12v. The coil that came with it was obviously very slow to heat steel or brass. I tried a black ferrite core with 3 wraps on each side. That did nothing to steel and slowly heated brass. Then I tried 4 wraps on each side with similar results. Then I tried a 1" coil with 7 wraps. That one seems to heat up the coil and heat sinks quicker than the target material. For the all the coils I made I used 12g solid copper. Any idea why everything over heated with the solid copper air coil?

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Old January 13, 2017, 09:59 PM   #139
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One heat sink definitely gets much hotter than the other. Even with the coil they provided. I can't see how this could be ran continuously.

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Old January 14, 2017, 08:44 AM   #140
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Kris,
Did you cut a slot in the ferrite?
A solid 'O' ferrite won't work, you need ends (poles) to focus magnetic energy

Ferrite has different values, I find 'Green' (painted or paint stripe) works best, but I have no idea how to test these things for their magnetic value, so I'm at the mercy of experimentation.
Maybe one of the EE's can explain the values and what we should be looking for...

Adding capacators have helped other people, increasing the 'Energy Tank' size.
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Old January 14, 2017, 10:04 AM   #141
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Jeep hammer. I did have a gate just large enough to fit a piece of brass in. It did heat up brass very slowly but had no effect on steel. It was black ferrite. I have green on the way.

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Old January 15, 2017, 03:24 PM   #142
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Jeep Hammer and Guys

Here is some more info along these lines, FWIW, (over my head) ,

http://forum.accurateshooter.com/thr...redux.3908353/

HTH,

Tia,
Don
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Old January 16, 2017, 10:52 AM   #143
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Nvreloader,
I can't remember if I posted this before on this forum,
I posted it on an electronics forum a while back.



Volts/Amps display, Volt/Amp control, timers for case drop through.
Nice door to keep little fingers from flipping switches, turning knobs, etc.
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Old January 17, 2017, 01:52 PM   #144
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That looks great. Really nice job!

Just got back from NC bringing a friend up to house & dog sit. I did stop in Columbus and picked up the power supply I mentioned earlier. Once we get back from the trip I'll get things setup and see if things work.

Ron
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Old January 17, 2017, 02:33 PM   #145
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I was able to get the 2 hp psu's wired in series for 24.8 volts. The worked quit well. Using a black ferrite core with 4 wraps of 12 gauge solid copper on each side I can heat a 30-06 case to 700 degrees in 15 seconds. I have some green ferrite on the way. I was hoping to get my time down to 1.5 seconds. Do you think switching to green ferrite rather than black will make that large of a difference? If not, what other methods can I use to get my heat time down?

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Old January 17, 2017, 04:10 PM   #146
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I honestly can't tell you.
I've experimented with 'Yellow', 'Red', 'Green' and an assortment of 'Not Marked' salvaged ferrite cores.
So far the 'Green' works best somewhere between 36 & 48 volts.

HP power supply modules in series is what I'm using.
There is a crap ton of them surplus since it's what they use for big servers & powering a lot of CNC/Digital controlled stuff.
I think I paid $12 each for mine off EBay, and once an I.T. Buddy saw them he brought me 4 more, the old ones when they updated a main server somewhere.

I'm thinking the 'China' units might not be the 'Right' switching frequancy, the more I read about this stuff.
Most of these things were made for solder melt pots or heating shafts/bearings for interference parts assembly,
And from what I'm reading brass *Might* need a different switching frequency to work at optimum.

I ordered a couple fine tuneable variable resistors to experament with that very thing.
The switching frequency is controlled by a resistor in the circuit, higher or lower value resistor changes the frequency.
This will let me make very slight changes to the resistor value and see if I can burn up another 'China' unit or two!

Being able to tune for 'Brass' instead of lead or tin or silver or steel -- *Should* (in theory anyway) let us use less expensive, commonly produced power supplies at lower voltages, bringing costs down and expanding capability & tuning ability...

SO! I'm off to inhale solder fumes in the name of a community project since my resistors came in today...
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Old January 17, 2017, 06:49 PM   #147
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kriss6600,

The original frustration may be due to the core material. You may have got too much inductance from it and choked current flow into the tank circuit too much to get adequate energy from it. The main symptom would be the frequency being detuned too far. That, alone, may prevent it from heating thin metal as well as you want, even when it is coupling energy into it.

You can adjust the inductance down by spreading the coils out over more length of the inductor, reducing the number of turns, or wrapping the core with paper or something to create space between the coil and the ferrite.

The right material should be for your frequency range. It also needs to be thick enough to produce the magnetic flux density you want before it gets too close to saturation. It should not produce a lot of heat loss at your desired frequency.
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Old January 17, 2017, 10:43 PM   #148
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I just checked what my amp draw is and it's 4.55. With the 24.8 volts I'm running that is only 112 watts. I'm wondering if I need to bite the bullet and buy another psu and go up to 36volts. I also took uncle nicks advice and reduced my wraps to 2 per side. The coils were already pretty well spaced. That reduced my time from 15 seconds to 10. It also made the coil itself heat up much faster. I'm curious as to why that is. I'm also curious as to what effect reducing or increasing the size of the wire used in the coil would have on the end result.

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Old January 18, 2017, 01:21 AM   #149
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Unclenick, can you explain how to test for what you were talking about?

Illustration might help...
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Old January 18, 2017, 01:50 AM   #150
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Here is one for you, 'Litz' wire!
That may very well be what I've been missing...

https://en.m.wikipedia.org/wiki/Litz_wire

High frequency AC, which this basically is with the alternating polarity, use 'Litz' wire instead of solid conductor or tubing.
I ran onto a dissertation on induction (heating) with values for 'Litz' wire over solid core conductors.

It never occurred to me we were working with high frequency AC properties (using a DC power supply) so it makes sense to beat surface conduction/skin effect using a bunch of insulated smaller wires would work better than a solid conductor, which works best for DC.

I got some high temp Litz wire on order, something else to consider & test.

Last edited by JeepHammer; January 18, 2017 at 01:58 AM.
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