Pulse Motors- Your building them wrong.

[MagnaProp]

I noticed something while playing with the neos and the tesla meter around the house. Placing the neo on certain pieces of metal around the house made its magnetic strength noticeably stronger. I tried metal railing, the metal drying machine frame, a small metal bell and the tesla meter could go up by 30mT or more depending on what it was attracted to. Could having the neo surrounded by a steel rotor, steel electromagnet core and steel keeper instead of aluminium or plastic, as I see a lot of motors built out of, be part of the reason the magnetic force is more than twice as strong when the same poles are facing each other in this build?

[MagnaProp]

I've hit a bit of a snag I think. I upped the current limit to 3 amps on my power supply and got up to 16v and 134mT. I noticed my electro mag getting very very slightly warm when on for about 10 seconds. I'm not sure how warm pulse motor coils usually get so I'm guessing I don't want to crank the amps more than the 3amp mark I am at now. This means my 134mT electro magnet still isn't close to a single neo's power of about 200mT.

This sounds like my electro magnet design may not be good enough. Tinman did say to add more wraps of copper but he didn't say to make the core longer. I'm thinking my longer core may have just added more eddy currents which defeated the purpose of adding more copper wraps.

I tried a smaller neo magnet, that is about half the size of what I'm presently using but it actually turned out to be stronger than the larger neo. I'm guessing the smaller size may have concentrating the field. I'm thinking about making a new electomagnet coil at this point. One with a shorter core and better bobbin that doesn't collapse on me.

[MagnaProp]

When making your coils, please keep the turn number high.
I will show you why here-->

Lets say we have a coil of say 300 turns, and it has a resistance of say 6 ohms.
This coil will draw 2 amps at 12 volts= 24 watts.
Magnetic field strength is determined by amp turns, and in the above case, we have 300x 2amp turns=600 amp turns.
If we wind a coil with say 600 turns, and it's resistance is 12 ohms, will still have the same amount of amp turns--600 amp turns, and
so our magnetic field strength is the same, only in the later case, we are now only using 12 volts @ 1amp= 12 watts of power.
We have halved our power consumption, but maintained the same magnetic field strength.

...

I'm trying to understand this better. I understand that amp turns is the amps times turns.

I don't understand how we got the 2 amp info in (2 amps at 12 volts= 24 watts.) from knowing only (300 turns, and it has a resistance of say 6 ohms).

So we started with 300 turns and 6 ohms resistance. How did we get the 2 amp value from that?

[bistander]

I'm trying to understand this better. I understand that amp turns is the amps times turns.

I don't understand how we got the 2 amp info in (2 amps at 12 volts= 24 watts.) from knowing only (300 turns, and it has a resistance of say 6 ohms).

So we started with 300 turns and 6 ohms resistance. How did we get the 2 amp value from that?

Hi Mag,
Haven't seen tinguy posting lately so I'll give it a shot.
Use Ohm's Law. V = I × R. Or I = V / R. So your 12 volt supply divided by the 6 ohm resistance of the coil takes 2 amperes to satisfy the equation.

When you double the # of turns on the coil from 300 to 600, you'll use twice the length of wire. Assuming it is the same gauge, twice the length will yield twice the resistance, 6 ohms to 12 ohms.

Now when you use Ohm's Law, the 12 volts are divided by 12 ohms yielding 1 ampere. But you now have 600 turns, so you still have 600 AT, (600 turns × 1 ampere = 600 ampere turns) same as before. But now, for the same the magnetomotive force (mmf or AT), you're using half the power ( 12W (12V×1A) vs 24W (12V×2A)).

You don't reduce the power required for free because you pay for twice the mass of copper, and associated space in your machine. But this is the method used in design to manage the heat. The lower wattage coil will run cooler.

Hope that helps.
bi

[Thaelin]

All:
    I am off line for a bit yet due to surgery's for skin cancer. Told all will be fine but added to heart issues, I am drug out. Another cut the 17th and two more mid Dec and will be out for a month. Will not have the use of my arms till Jan 10th they say. I will make it but have to deal with the garbage that follows.
                               Not asking for sympathy at all, just why I am not moving. Rotor and housing is done and ready.


Mags:
    The coil I have is an old wire spool from RS with 2 strands of #20 looped to one and will draw about 3 amps if I let it. Will in fact tho repel the 2 N43 .5 X .5 inch neo's. I am shooting for 15v due to the recover circuit I will add and the NiMi batt pack. The other coil I wound with #24 and 400 turns would not exit the magnets at all. Not really schooled in how to design a coil for a specific situation. Since I will be harvesting the kickback to around 90%+, I should be able to keep the input down to a minimum.


thay