Self accelerating reed switch magnet spinner.

[TinselKoala]

I'm pretty sure I'm not saturating my cores. How much field strength do you need to saturate a nylon bolt?

[MileHigh]

TK and All:

I suppose it's a generational thing for nerds.  In the late 70s and 80s (for my experience) many people will remember all of the deep navy blue National Semiconductor data books.  In their op-amp data book there was this huge section with application notes for op-amps showing many amazing and useful op-amp circuits.  Some readers may still be wondering what the hell op-amps are and what they are really useful for.

So I did the Google search and wouldn't you know it, the search was "built in" to Google because so many people must have searched for the long-lost op-amp application notes that young nerds used to lust after.

The built-in Google search is, "national semiconductor op amp application notes."

Good link that came up right away:  http://www.ti.com/ww/en/bobpease/assets/AN-31.pdf‎

The actual doc is attached below because it is so good.  For newbies, take a look at the op-amp circuits, it will blow your collective minds.  Also, you will see in most if not all of the op-amp circuits they call out for a specific model of op-amp.  You have to take that with a grain of salt, that's mostly National Semiconductor trying to sell their own op-amps.  For the majority of the circuits, just about any op-amp will do.  By the same token, not all op-amps are created equal.

What should be readily apparent is that if you want to take the plunge and buy 10 or 20 op-amps from DigiKey, is that they can do amazing things.  They can do amazing things with respect to mathematical operations using voltages as variables and they can do all sorts of signal processing applications like high-pass and low-pass filters, etc.

Think of an audio mixer.  An audio mixer is simply a circuit that adds voltage signals together.  You can do that with your eyes closed with an op-amp.  Many people talk about things like "putting two frequencies into a coil at the same time" as a hypothetical example.  You can use an op-amp as part of a circuit to do that.

MileHigh

[TinselKoala]

Yes, that's a great classic text all right, thanks for finding it. I found the Sams classic "Op Amp Cookbook" by Walter Jung in the used bookstore a few weeks ago and of course I scraped together my lunch money to buy it.

All op amps are not created equal. Many really do need the bipolar power supply to do their best work (like your analog power computer). Many can be used in single-supply mode as we have been doing. Some are more better for audio work, some are best for comparator applications, some are general purpose, some require dealing with more input and output options rather than just the two ins and one out of the opamps in the TL082 chip. Apparently I once again "aced" accidentally by choosing the TL082 for this application because of the very high impedance JFET input stage and the fast slew rate, and the fact that it works well on the single supply mode. And ease of use, low cost, and easy availability.

Here's something I found just a couple days ago, which made me very excited. This is another "classic" from a bygone era. The chips it talks about are still available, and many of them exist now in advanced versions that use very low power and are very sensitive. There are many many useful circuits and concepts covered in the TTL Cookbook.

ftp://apollo.ssl.berkeley.edu/pub/cinema/04.%20Science/TTL%20Cookbook_0672210355.pdf

It's a 12 MB pdf, an excellent scan, all 340 pages, clear diagrams and even the photos aren't too completely black.

ETA: I just checked EBay for sellers of TL082CN .... if you are willing to wait two weeks for a shipment from Thailand, you can get 10 for $2.79, free shipping. Or.... 50 for $9.99 from the same seller in Bangkok.
Twenty cents apiece! Delivered to your door! How can this even be possible at all?

[MileHigh]

TK:

Thanks for the link to Dan Lancaster's TTL Cookbook.  Somewhere in the past we probably also discussed his famous CMOS Cookbook.  TTL chips are probably still available, even in archaic DIP packages.  There is probably so much military hardware that is still in use that makes use of MIL-grade TTL logic chips in DIP packages that they still keep a semi operation somewhere that can manufacture them.  Honestly, I am just speculating.  There could be a government "strategic reserve" of them somewhere too and they are no longer being manufactured.  Even through they are no longer being manufactured, they may be available commercially for many years on the secondary brokerage market.  There could be many many millions sitting in inventory on shelves all over the world.

If you remember looking at the first IBM PC-XT and AT motherboards, they were big grids of TTL (or NMOS?) chips.  Same thing for the Apple II.  In modern hardware design engineering, that technology has been long gone.

Twenty cents apiece! Delivered to your door! How can this even be possible at all?

I don't know!  I know that you can get stuff manufactured in Shenzhen in mass quantities at low low prices, but I don't know much at all about the Asian semiconductor manufacturing industry.  I do know that most of the semiconductor fabrication plants are in Asia, and many in the US have closed down.  One more time, that could one day have geopolitical strategic importance and become a major issue.

Playing with spinny things is less stressful and more fun.  lol

MileHigh

[MileHigh]

I caught a mistake I made for the supercharged coil power analysis.   Note this is all about the resistive power losses in the coil, this is not about the power exported to the outside world by the stronger and faster-rising magnetic field pushing on the rotor.  I didn't even mention that which was another mistake.  That "export" power manifests itself as a (voltage drop inside the coil x the current flowing through the coil) and does not heat the coil.  You can't directly measure this "voltage drop due to power exported to the outside world," but you know it is there.

This may be counter-intuitive to some people but look at it like this:  You know the only form of power input to the coil is (voltage x current.)  You know the coil is exporting power to the outside world because because the rotor is turning.  That means that the export of power to the outside world has to "eat" a slice of the (voltage x current) input power.  This simply has to happen, and exactly the same process happens with a conventional electric motor.  The power to make the rotor spin is not coming from "nowhere."

So, back to the resistive power analysis that does indeed heat the coil.

So there is your supercharged drive coil:  You double the magnetic field strength of the drive coil if you split the coil into two halves and you decrease the energizing time constant by one half.  Nothing is stopping you from splitting it into three or even four if you want to.

Of course it goes without saying that when you do this you pay a price for this:  You double the current consumption and you double the power consumption of the drive coil also.

The resistive power dissipated in the original 100-turn coil:

We have one ampere and one unit of resistance so the power dissipated is = (one-squared x R) = R

The resistive power dissipated in the 50-turn coil:

We have two amperes and one-half unit of resistance so the power dissipated is = (two-squared x R/2) = 2R

We have two 50-turn coils so the total resistive power dissipated is 4R.

Conclusion:  When we split a 100-turn drive coil into two 50-turn drive coils the resistive power losses go up by a factor of four.

So let me finish this off by taking another look at the pure resistive losses in the coil vs. the power exported to the outside world to make the rotor spin.

Here is a thought experiment:

Setup #1:

Suppose that you have your 100-turn coil in your pulse motor and the rotor is locked so it can't turn.  You pulse the rotor and your sophisticated measurements tell you that the average power supplied to the drive coil is 10 watts.   In this case all of the 10 watts supplied to the drive coil will be converted into heat power that heats up the coil.

Setup #2:

Suppose that you have your 100-turn coil in your pulse motor and this time the rotor is free to spin.  You pulse the rotor and your sophisticated measurements tell you that the average power supplied to the drive coil is 10 watts.   In this case less than the full 10 watts of power supplied to the drive coil will be converted into heat power that heats up the coil.

It simply has to be due to the conservation of energy.  You could easily confirm this by monitoring the temperature rise of the coil over time.  And with some fancy footwork with your scope and provided that you knew what you were doing you could "see" this also.

The key issue here is to be able to visualize the flow of power.  If the drive coil is making the rotor spin then power is "flowing" out of the drive coil into the outside world.  If you really want to analyze what your pulse motor is truly doing then you have to be conscious of this.

That begs the question:  How much power is being dissipated in the rotor when it spins?  The assumption being that that power is coming from the drive coil, there is no other place!  That implies that you do a measurement of the moment of inertia of your rotor and then do some spin-down measurements.  That way you will know the rotor power dissipation as a function of RPM.  That's interesting information that may come in handy.  If you make very precise measurements, you should be able to see a non-linear curve which would tend to indicate the effects of air friction.

MileHigh