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Induction brass annealer redux

An example of a multiturn precision pot-

http://www.mouser.com/ProductDetail...ygUB3GLcD7uAamKpu9okKBJOkWszRqCBTTBgNVEwiFQ==

These are nice, used this one before. Overkill for this application. BTW you want a linear taper, not audio or log taper. 2 to 3 turn is plenty of precision, 10 turns and up is total overkill.

Single turn precision pot-
http://www.mouser.com/ProductDetail...=sGAEpiMZZMvygUB3GLcD7pgRzBTjLH3PNFIrrU5LGEU=

Something like this is more appropriate. Should be able to find a similar product cheaper.
 
An example of a multiturn precision pot-

http://www.mouser.com/ProductDetail/Vishay-Spectrol/533B1502JC/?qs=sGAEpiMZZMvygUB3GLcD7uAamKpu9okKBJOkWszRqCBTTBgNVEwiFQ==

These are nice, used this one before. Overkill for this application. BTW you want a linear taper, not audio or log taper. 2 to 3 turn is plenty of precision, 10 turns and up is total overkill.

Single turn precision pot-
http://www.mouser.com/ProductDetail/CTS-Electronic-Components/282T33L502A26C2/?qs=sGAEpiMZZMvygUB3GLcD7pgRzBTjLH3PNFIrrU5LGEU=

Something like this is more appropriate. Should be able to find a similar product cheaper.

Thanks for the info...this is great! I found this 5k pot on Amazon; looks like it will work. https://www.amazon.com/gp/product/B003IXVGB8/?tag=accuratescom-20
 
Yeah FishinDog that will work fine.

I'm thinking hard on the multiple position switch for current control, think it might be better in the long run, because you are adjusting in discrete steps that are repeatable every time. Besides I have two 10 position switches laying around from a past project.
Lots of ways to skin the cat and they all work.
 
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Yeah FishinDog that will work fine.

I'm thinking hard on the multiple position switch for current control, think it might be better in the long run, because you are adjusting in discrete steps that are repeatable every time. Besides I have two 10 position switches laying around from a past project.
For high volume and different calibers the switch would be quick and easy changeover by creating a simple table or even labeling the switch. I like it!

I'm going to try and adopt my hopper off my home built propane annealer (see pic). Adding a second timer/relay and solenoid to release a shell from staging above the annealing coil. Still "noodling" how to funnel the shell from horizontal white hopper wheel to vertical staging. I might add your I/R sensor circuit to trigger the hopper motor feed. My current hopper motor and variable controller is continuos duty though, so I may need to rethink starting and stopping it for every shell. Gotta love the journey of design & build!

IMG_1685.JPG
 
I'll draw up a diagram and the formula for figuring out the resistance values for the switch. Its fairly simple, it replaces the pot in the previous diagram.

Formula is this-

Vout = Vin x (R2/R1+R2)

In this case R2 is a parallel resistance so we need to calculate equivalent resistance.

Result for R2 is 3.75K. Now we vary R1 to get our target voltage to dial in the desired current limit.

Vout= 5v x (3750/?+3750)

Suggested common resistor values by switch position (10 position switch)-

150, 270, 270, 270, 330, 330, 330, 390, 470, 0.

Switch position, voltage, target current-

#1 4.81v, 15.1A
#2 4.50v, 14.1A
#3 4.22v, 13.2A
#4 3.98v, 12.5A
#5 3.72v, 11.7A
#6 3.49v, 11.0A
#7 3.29v, 10.3A
#8 3.08v, 9.7A
#9 2.86v. 9.0A
#10 5.0v (no resistor) full power available "for testing purposes only"

#6-#9 probably never use unless you have very small low mass cases. A 5 or 6 position switch would likely result in all the range you'd need.


clip_image0236.jpg
 
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I'll draw up a diagram and the formula for figuring out the resistance values for the switch. Its fairly simple, it replaces the pot in the previous diagram.

Formula is this-

Vout = Vin x (R2/R1+R2)

In this case R2 is a parallel resistance so we need to calculate equivalent resistance.

Result for R2 is 3.75K. Now we vary R1 to get our target voltage to dial in the desired current limit.

Vout= 5v x (3750/?+3750)

Suggested common resistor values by switch position (10 position switch)-

150, 270, 270, 270, 330, 330, 330, 390, 470, 0.

Switch position, voltage, target current-

#1 4.81v, 15.1A
#2 4.50v, 14.1A
#3 4.22v, 13.2A
#4 3.98v, 12.5A
#5 3.72v, 11.7A
#6 3.49v, 11.0A
#7 3.29v, 10.3A
#8 3.08v, 9.7A
#9 2.86v. 9.0A
#10 5.0v (no resistor) full power available "for testing purposes only"

#6-#9 probably never use unless you have very small low mass cases. A 5 or 6 position switch would likely result in all the range you'd need.

Hi Grocmax,

My electronics knowledge is a bit lacking but I would like to learn more about this subject.
Could you explain to me (in layman's terms LOL) what is the advantage of keeping the current constant?
If you keep the current from going up but then the voltage rises you would still draw the same amounts of watts right?
So would that not mean the same output on the coil?

Thx.
 
Its an attempt to gain further control- consistency and easy repeatability by clamping the voltage and current to an upper limit. The induction board is dumb, will take whatever power you put to it till it blows up. The current draw is very dependent on the case size, wall thickness, and position within the coil. Also the power supplies have an upper limit on what they will produce while staying happy and not going into fault.
 
Got my new HD relay in so I can make some test runs. Word on automotive relays- they ain't all created equal. Parts store no-name 40A 12v gonna stick the contacts, this one works just fine so far-

http://www.mouser.com/Search/Produc...tualkey65500000virtualkey655-V23234-A1001X033

Here's a 10 case test run at a voltage clamp of 46v and the current limit input set to 5v (100% max rated current). Not sure I trust what the ammeter is telling me in absolute numbers, but it will work for relative changes. Anneal times are quick on a 223 case as you can see.

 
Got my new HD relay in so I can make some test runs. Word on automotive relays- they ain't all created equal. Parts store no-name 40A 12v gonna stick the contacts, this one works just fine so far-

http://www.mouser.com/Search/Produc...tualkey65500000virtualkey655-V23234-A1001X033

Here's a 10 case test run at a voltage clamp of 46v and the current limit input set to 5v (100% max rated current). Not sure I trust what the ammeter is telling me in absolute numbers, but it will work for relative changes. Anneal times are quick on a 223 case as you can see.


Ahhhh, see you already know about this :oops::eek::rolleyes:o_O
 
Yeah you gotta get one that's rated a little better on the contacts than the cheap stuff. Funny part is the crappy Autozone/NAPA/O'Reilly's relay is more expensive than the good one that works.
 
Re the question on "why current limit;

If you take, for example, a power supply that is set for 50 Volts
and also has a settable current limit, say 20 Amps. This yields a maximum of 1000 Watts. If you limit the current to 10 Amps. the load you are attaching to the supply will have a resistance that for example is 20 Ohms, The 10 Amps will develop 20 Volts when passing through 10 Ohm. (E=I X R) By limiting the power supply to 10 Amps, the power supply will sag down to 20 Volts, the voltage needed to supply 10 Amps in this load. The power now delivered to this load is 200 Watts (P=I X E). If you increased the current limit to 15 Amps, the corresponding load Voltage would be 30 Volts (E=I X R) and the associated power would be 450 Watts ( P=I X E) So, by increasing the current by 50% increases the power by 225%! that is because you increased the current limit which also increased the voltage across the load and they cause the power to increase by the multiple of both not simply the increase of one item.

The load is dissipating 450 Watts and the power supply is delivering 450 Watts. The actual power into the power supply from the AC line will be more than 450 Watts due to 1. the power supply may have an efficiency of 85 % and 2. there may be ancillary loads on both the line and the power supply such as other power supplies tied to the AC line to develop maybe 5 V for some logic circuits and maybe some drive circuits associated with the power oscillator driving the load coil that needs 10% of the power entering the oscillator and the oscillator only delivering 90% of the power entering.
So, in our example, we had 450 watts in the load. We then had
495 Watts being delivered by the power supply to the oscillator stage.
Therefore, the power supply is supplying 495 Watts and it is 85% efficient so it is consuming 585 Watts from the line. And our annealer is also using 5 Watts (example) to drive the logic so the power supplied from the line is 590 watts. If you remove the load (the annealed case) the current drops significantly as we still have 5 Watts driving the logic as well as, in this example, 45 Watts powering the drive circuit of the oscillator for a total of 50 Watts. The load on the power supply will be more than 45 watts as we limited the load current of the supply to 15 Amps and the associated power supply voltage sagged to 30 Volts. But, with the load no longer loaded by 10 Ohm, the current dropped to 1.5Amps which is the drive current needed by the oscillator so our power supply is no longer in current limit so the voltage rises to 50 volts which now is 75 Watts (P=I X E) or 75 = 50 X 1.5.
This is why the current drain still may be kind of high when there is no case in the work coil. The example we used may be way less than real as there are a lot of losses in the system when no load is in the work coil. Those losses account for the idling current. The oscillator is designed to be very efficient while supplying rated load and may be VERY inefficient when idling.
 
I like the lower wattage annealers. It should keep you in the annealing temp range a tiny bit longer? An interesting test I would do if I had an induction annealer is to anneal one case ten times at your preferred setting and see if it gets noticeably soft. Your at the lower end of the annealing temp for so little time that you may be stress relieving and not annealing? Just an attempt to learn something nobody has done. I don't mean in any way that the annealers on this website are not doing a good job. You guys are doing a great job. I wish I had one. Just a curiosity. I have been doing metallurgical quality control and failure analysis for many years. You cannot go to a higher temp but you can do multiple anneals. It would be nice if we had hardness testers that could determine case hardness after annealing. It's not really necessary. I use a torch for a small number of cases. 6BR casual short range BR and ground hog hunting.
 
Webster,

That is very valuable information!
I have often thought that using max power so you can "anneal" in 1.5 sec or so was not really appropriate. I have 2 or 3 sets of Ferrite cores for my Annie as well as a solid copper work coil and the water cooled coil. I actually prefer to anneal with 3-4 sec but your idea sounds to be a better way to get consistent anneals.

I will be doing some testing to find a short cycle that gets the neck to 750 then repeat a couple times.

Most folks that are still building their induction annealers think they need automatic fixtures to speed up things, but in reality you can anneal without any fixturing so fast that it is a waste of effort to automate the procedure. One can anneal with induction almost as fast as it takes to load hoppers for an automatic rig!
 
I'm not sure what to call it, technically it isn't true annealing where its held to the anneal temp for the full time required.

AMP makes the nifty commercially available unit, and they pulse heat, 5 or 6 strong pulses a short time apart.
 

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