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### Author Topic: Self accelerating reed switch magnet spinner.  (Read 288166 times)

#### MileHigh

• Hero Member
• Posts: 7600
##### Re: Self accelerating reed switch magnet spinner.
« Reply #90 on: October 07, 2013, 07:03:31 AM »
Bill:

I wanted to comment on this but it got lost in the shuffle.

Quote
Didn't click the link yet but this sounds a lot like the Babbage engine?

Yes indeed, you are correct.  If I recall correctly Charles Babbage spent many years trying to perfect the "Analytical Engine" machine but the machining and parts and materials were just not available at the time.  So he had the correct system but he could not fully realize it in a working model.

So the ship's firing computer is a giant working Babbage machine.   Here is a simple typical example pulled from the film:  Imagine a 10-foot-long cylinder about three feet in diameter.  You can see that the "cylinder" actually has a sculpted odd-looking shape.  The cylinder rotates about it's axis and there is a cam on a plunger that rolls over the cylinder so that it can register the radius of the cylinder at any point on the cylinder (you will see it in the movie if you watch it.)

Now, supposing that the angle that you turn the cylinder on the shaft varies between 0 and 10.   Let's call that the variable A.  Supposing that the linear distance along the cylinder varies between 0 and 10.  Let's call that the variable B.

You make the shape of the cylinder so that any point on the cylinder has a radius of [Sqrt(A x B)]

So if you can imagine the cylinder rotating on it's axis, and a cam that moves along the length of the shaft that measures the radius of the shaft - then if you sculpt the cylinder properly you get the square root of the product of the two variables in real time.   I probably and not describing it that well but it's worth it to watch the movie if you are interested.

MileHigh

#### TinselKoala

• Hero Member
• Posts: 13958
##### Re: Self accelerating reed switch magnet spinner.
« Reply #91 on: October 07, 2013, 03:16:37 PM »
Imagine this:

#### TinselKoala

• Hero Member
• Posts: 13958
##### Re: Self accelerating reed switch magnet spinner.
« Reply #92 on: October 07, 2013, 04:25:51 PM »
The present state of the schematic:

#### MileHigh

• Hero Member
• Posts: 7600
##### Re: Self accelerating reed switch magnet spinner.
« Reply #93 on: October 07, 2013, 04:38:26 PM »
TK:

Congratulations on an excellent job!  Having an updated schematic is very much appreciated also.

Magluvin:

I told you not to engage with me and I mean it.  And your answer is close but not quite right.  When the rotor magnet is moving across the center of the large sense coil there is no change in total magnetic flux through the loop with respect to time so the EMF generated by the coil will be zero.  In this case it's EMF and not current that is the relevant parameter, there is no current flow through the coil.

I sent you an email that you read this morning telling you to remove your quoting of me in reply #88 and you didn't do it.

DO NOT ENGAGE WITH ME ON THE FORUM.

I made an exception in this case and responded to you, but it likely will never happen again.

MileHigh

#### TinselKoala

• Hero Member
• Posts: 13958
##### Re: Self accelerating reed switch magnet spinner.
« Reply #94 on: October 07, 2013, 04:48:25 PM »
Coil data:

Sense coil: Carefully removed from a television set SPST relay, 24VDC coil, coreless. DC resistance 273 ohms. Inductance 33 mH (by ProsKit meter, may not be accurate due to high resistance of coil.)

Drive coil: Bobbin made with center phenolic tube, 1/4" ID, 3/8" OD. Winding 1 5/8" long x 2" diameter, wound full with #27 enameled magnet wire. Center tube can accept 1/4 inch bolt or rod core, but has a plastic threaded rod mounting it in the photo above. DC resistance 62 ohms, inductance 145 mH.

#### TinselKoala

• Hero Member
• Posts: 13958
##### Re: Self accelerating reed switch magnet spinner.
« Reply #95 on: October 07, 2013, 08:05:10 PM »
A request for more help:

The 4017/555 system fires a very short pulse to the blue LED just at the moment of coil turn-on. It would be _awesome_ to have another strobe LED -- say a red or green one -- that fires just when the coil turns _off_.

This then would allow full control and visualization of the dwell angle, or conduction angle as MH refers to it, without needing a scope ever.

But I can't quite figure out how to get a pulse at the turnoff time. My brain is fried at this point, creative juice is low. So I'm asking for some help from the audience. How can I get a pulse at the turn-off time that I can use as a strobe signal?

I have a hunch that the LM339N quad comparator chip might be very useful in this application.

• Hero Member
• Posts: 1842
##### Re: Self accelerating reed switch magnet spinner.
« Reply #96 on: October 07, 2013, 08:28:51 PM »
A request for more help:

The 4017/555 system fires a very short pulse to the blue LED just at the moment of coil turn-on. It would be _awesome_ to have another strobe LED -- say a red or green one -- that fires just when the coil turns _off_.

How can I get a pulse at the turn-off time that I can use as a strobe signal?

Just an idea:

You take a second "4017/555 system" (a copy of the one you have in place), but you put a NOT gate (4069 hex inverter, just one inverter) in front of it.

You connect the input to the NOT gate at the same point in the circuit where the first "4017/555 system" is connected (there is an arrow in the circuit with the text "TO 4017 PIN 14").

So, the first "4017/555 system" fires (or better said "clocks") whenever the coil (IRFP360) is switched on, and the second "4017/555 system" (with the NOT in front) fires (or better said "clocks") whenever the coil (IRFP360) is switched off.

#### TinselKoala

• Hero Member
• Posts: 13958
##### Re: Self accelerating reed switch magnet spinner.
« Reply #97 on: October 07, 2013, 10:18:47 PM »
Hmmm...thanks, that would work I think. I'll see if I can rig it up. I have another 4017 chip, I think. And to save space a 556 dual timer could be used.

Can you think of a way to use the second op-amp in the TL082 instead of the NOT gate?

#### TinselKoala

• Hero Member
• Posts: 13958
##### Re: Self accelerating reed switch magnet spinner.
« Reply #98 on: October 07, 2013, 11:42:37 PM »
Haven't figured it out yet?

Simply use the second op-amp but with the inputs reversed. The JFET input stages can be paralleled with no problem at all.
The first comparator flips state to HI when the input rises above the setpoint and turns the coil on, and goes LO when the coil goes off. The second comparator behaves in reverse, it goes HI when the input falls below the setpoint and the coil goes off.

So all that's needed is three little wires to hook up the second comparator in the TL082, and another 4017/555 combo, which could use the second half of a 556 dual timer, probably. Or one can simply swap the input connection to the one 4017/555 over to the second comparator output, as I am doing at the moment.

#### MileHigh

• Hero Member
• Posts: 7600
##### Re: Self accelerating reed switch magnet spinner.
« Reply #99 on: October 08, 2013, 12:35:52 AM »
Hey TK:

I am really tired today so all I can offer is a Google search that looks pretty good, "555 falling edge trigger."  You might find some good circuits that demand as input a brief negative going pulse.  That might no be too compatible with what the comparator output is doing in the sense that it stays low for a "long" time.  However, to get around that you just need to put a small cap between the comparator output and the 555 circuit that expects a brief negative going pulse to trigger the monostable.  So the cap will couple the falling edge to the 555 trigger input.

Also, you put a pull-up resistor on the 555 trigger input.  (You may also want to put a diode connected towards +12 volts to snub out any over-voltage on the 555 trigger input when the comparator output transitions from low to high.)

So when the comparator output goes from low to high, the capacitor has roughly +12 volts on both sides and it's not charged.

Then when the comparator output goes from high to low, the 555 input sees that high to low transition and that triggers the 555 monostable to flash the second LED.   Then while the comparator output stays low the pull-up resistor charges the cap and the 555 is "satisfied" because it sees a HIGH on the trigger input again - i.e.; the 555 trigger input (possibly) only wants to see a very brief negative pulse that is much shorter in duration than the monostable output that flashes the LED.

Typically it's a very tiny capacitor that will do the trick.  Perhaps a 0.1 uF cap.  Then you might want the falling edge trigger to be low only for a few hundreds of microseconds.  So you choose an appropriate pull-up resistor using the RC time constant.

It's a "quasi kluge" that should work just fine, and all you need to implement it is a negative edge triggered 555 monostable circuit.

MileHigh

#### TinselKoala

• Hero Member
• Posts: 13958
##### Re: Self accelerating reed switch magnet spinner.
« Reply #100 on: October 08, 2013, 12:36:15 AM »
I had to take it apart to reglue a magnet, so here's the underside view of the rotor, showing the assortment of magnets. It's all I had available when I made the original Bedini SMG that I am recycling!

#### TinselKoala

• Hero Member
• Posts: 13958
##### Re: Self accelerating reed switch magnet spinner.
« Reply #101 on: October 08, 2013, 12:40:06 AM »
Hey TK:

I am really tired today so all I can offer is a Google search that looks pretty good, "555 falling edge trigger."  You might find some good circuits that demand as input a brief negative going pulse.  That might no be too compatible with what the comparator output is doing in the sense that it stays low for a "long" time.  However, to get around that you just need to put a small cap between the comparator output and the 555 circuit that expects a brief negative going pulse to trigger the monostable.  So the cap will couple the falling edge to the 555 trigger input.

Also, you put a pull-up resistor on the 555 trigger input.  (You may also want to put a diode connected towards +12 volts to snub out any over-voltage on the 555 trigger input when the comparator output transitions from low to high.)

So when the comparator output goes from low to high, the capacitor has roughly +12 volts on both sides and it's not charged.

Then when the comparator output goes from high to low, the 555 input sees that high to low transition and that triggers the 555 monostable to flash the second LED.   Then while the comparator output stays low the pull-up resistor charges the cap and the 555 is "satisfied" because it sees a HIGH on the trigger input again - i.e.; the 555 trigger input (possibly) only wants to see a very brief negative pulse that is much shorter in duration than the monostable output that flashes the LED.

Typically it's a very tiny capacitor that will do the trick.  Perhaps a 0.1 uF cap.  Then you might want the falling edge trigger to be low only for a few hundreds of microseconds.  So you choose an appropriate pull-up resistor using the RC time constant.

It's a "quasi kluge" that should work just fine, and all you need to implement it is a negative edge triggered 555 monostable circuit.

MileHigh

That's not a quasi-kludge, it's a fullblown grownup kludge.

Did you miss my post above, Analog Op-Amp Man?

The TL082 has two opamps in it and all that is needed is to reverse the inputs, put the reference voltage from the setpoint pot into the non-inverting input and the sense coil into the inverting input of the second opamp. It seems to work fine, so far.

#### TinselKoala

• Hero Member
• Posts: 13958
##### Re: Self accelerating reed switch magnet spinner.
« Reply #102 on: October 08, 2013, 01:50:33 AM »
So here's yet another schematic, showing how to hook up the second op-amp in the TL082 to do the trick. I just use the same 4017/555 combo for now but will make another setup with a 556 and a second 4017. So the chip count will be 4, but most of that will be for the strobes.

#### synchro1

• Hero Member
• Posts: 4720
##### Re: Self accelerating reed switch magnet spinner.
« Reply #103 on: October 08, 2013, 02:15:37 AM »
@TK,

This circuit looks like it may spring to life by lightning strike. Watch it now! Maybe your dog can help lick clean what's left of the peanut butter from inside the lid.

#### MileHigh

• Hero Member
• Posts: 7600
##### Re: Self accelerating reed switch magnet spinner.
« Reply #104 on: October 08, 2013, 02:22:51 AM »
TK:

Ah! Ha!  I get it now.  It did not register with me that you get two op-amps for \$0.71!  So there is your logic inverter and you can trigger another 555 and do your divide by four.  I assume that you are getting ready to wrap this one up soon but are you sure that you need two CD4017 chips?  You can't do it with just one counter? Don't mind me!

Notice your pulse control logic is is fixed at +12 volts but the power to the drive coil is like a free range chicken.  So you could play mad scientist and raise the potential on the drive coil to some really high voltages if you wanted to, and put on a Kevlar vest and some Gucci designer mad scientist goggles.  Just go insane!  (remember protection diodes)

I think you might need to route the coil energy into a battery or something if you go the insane route.

Another phenomenon that you might want to explore is this notion that sometimes the current flowing through the coil never stops flowing between energizing pulses.  Like man, it's constantly circulating.  In some pulse motor setups with a conventional diode discharge in to a charging battery the experimenter might not even be aware that this is happening at a high RPM.  That actually represents a danger.  You put your pulse motor on high speed, the phone rings and you go into another room and start chatting.  When you come back 20 minutes later your coil is a red hot blob about to eat its way through the table.

MileHigh