help please electric motor

[lotec]

Hi there,
I havnt posted in the energy section before but i have followed quite a few of the threads.
I am having a bit of trouble with a coil triggered monopole motor. Ive tried it with a couple of circuits, 1 ssg minus the charge battery,, and another similar type circuit and they both do similar things. When i push start them the coil vibrates on and off continuously until the circuit is broken. It makes a whistling
sound about the pitch of a mosquito and is loudest when the coil is under the magnet. oh and the rotor dosnt turn
,
Has anyone else had this problem or know why the coil is turning on continuously regardless of what the rotor is doing.
The coil is an air coil wound around 5 mm OD nylon tubing. The trigger and the drive coil are both 0.3 mm roughly. I wound them together side by side at the same time.The trigger has 850 turns and the drive about 1000 the trigger wire ran out first so I pulled the end to the side and kept winding the drive coil for a hundred and fifty more turns. The trigger is 13 ohms and the drive is 15 ohms and they are not shorting between them. the outer diameter of the coil is slightly bigger than that of the magnet.

Thank you in advance, Once i get to the bottom of this mystery i will have learned me something new ,is it because the The two filaments might have a tight inductive coupling .. i did not expect this

Thanks again
regards wil

[mbrownn]

It sounds like it is self oscillating, it should work like that to charge batteries but if you want the wheel to run try putting in an iron core.

[gyula]

I agree, it has become an oscillator, check the sense of the windings again and try to reverse the ends of the trigger coil.

[Peculian]

Something else to consider is to add more resistance at the base of the transistor where trigger coil is connected.

[lotec]

thank you mbrownn gyula and peculian for taking the time to help me out with this, I will try your sugestions

[lotec]

still at it

I tried hooking up the wires all different ways. Then I tried different resistances at the base of transistor and this changed frequency of the vibrations. Then I put a mild steel bolt through the middle of nylon tubing in core. This cured the oscillation problem. The motor almost worked. I now believe that the trigger winding is not making enough voltage to turn the transistor on enough. The nylon tubing core is only big enough to fit a 4 mm bolt in. This brings me to my next question. If someone reading this has made air cores with triggers that make enough turn on voltage I would be grateful to hear from you. I am resigned to winding a new coil. Have I made the center of the core too small?
Is it true that the center of a generator coil should be slightly wider then the outside diameter of the magnet to avoid a cancelling effect as the flux lines may cross the wires on both sides of the core center at the same time? I have a feeling i may have read that or i remembered it wrong. So sorry to bore unsuspecting readers with silly questions.
Thanks again
regards wil

[tachyoncatcher]

More Iron

Hello lotec,
If its a motor you want, you will need more iron! Your winding are sufficient for the trigger and drive coil. What is missing is the magnetic concentrator, the iron core. I have tested core sizes from 30mm to 10mm, all other geometries being the same. I can run 10mm core, but it is slow to start. I use another, hand-held motor to spin it over 1000rpm, then it will run just fine. You can use a small core, but you'll need more voltage to turn the rotor. Thats been my experience anyway.
Randy

[lotec]

Thanks Randy, I appreciate the advice and I will make coil with a chunkier core.
Practical experience is a wonderful thing, something I dont have much of.
Wil.