Electric Motor Secrets

[Jetijs]

Thank's Peter
I did not know, that a reedswitch can operate that fast. This is great
As for the coil wire. What about those cables with insulation? Can I use these? Because it is hard to get the magnet wire of that thickness here, but I can get a cable with insulation at every store.
Of course the insulation would reduce the total count of the windings, but that is what is available here. I could order some magnet wire form ebay, but that would take weeks to deliver and would be more expensive. I don't see why i could not use such a cable instead of a magnet wire. What do you think?
Thank's
Jetijs.

[lighty]

@Jetijs
@nali2001

I didn't know it's so hard to get the transformer silicone steel. It's extremely cheap here and easily obtainable and I used it many times for various purposes. Some of the forms I made were quite complex but as you know it can easily be cut by water and laser (depending on the required precision and the thickness of silicone steel plate). These days I prefer to use the Mu-Metal cores but I rarely do because the material is rather expensive.


@Peter Lindemann

Reed switches are a great little component but they do suffer from slow turn-on times and slow turn-off times (a few orders of magnitude longer periods in comparison to semiconductor devices). Fast turn-on and turn-off periods are useful in more than one way and especially if you're into energy recycling. As for the bias currents, they're extremely low- for example an optical switch with three stages of level adjustment and logic control consumes about 30mA at 12V -> 0.36W. In comparison to the overall consumption of any motor it's negligible.

That being said- I do recognize that reed switches are much simpler to work with and probably the best choice for fast and simple experiments.

[Jetijs]

Lighty, where are you from, if you can get this silicon steel so easy? Where are you getting this steel? Maybe someday you could ship some of these steel plates to me, for a reasonable price of course

[lighty]

I'm from Croatia. The transformer silicone steel is cheap but I'm not sure how much would shipping cost since the steel is heavy as hell.

As for the Mu-Metal we get it from Germany.

[Jetijs]

I live in Latvia, that is not too far away
Got any links form mu-metal manufacturers in Germany?

[Peter Lindemann]

Try the #21 Wire First

Thank's Peter
I did not know, that a reedswitch can operate that fast. This is great
As for the coil wire. What about those cables with insulation? Can I use these? Because it is hard to get the magnet wire of that thickness here, but I can get a cable with insulation at every store. Here's a picture:


Of course the insulation would reduce the total count of the windings, but that is what is available here. I could order some magnet wire form ebay, but that would take weeks to deliver and would be more expensive. I don't see why i could not use such a cable instead of a magnet wire. What do you think?
Thank's
Jetijs.

Jetijs,

If you have the #21 wire, just start with that. Wire with normal insulation on it just takes up too much space, and does not cool very well, either. Start with 250 turns of #21 and see how it runs. If it seems speed limited, remove 50 turns and test again.

An alternate idea is to wind two or three coils (bifilar or trifilar) with about 100 turns each and then switch them in parallel, running each winding with its own transistor.

I do not recommend spending more money on Mu Metal or other wire at this point. Get the motor running with what you have.

As for collecting energy from the turn off of the circuit, the reed is "slow" to actuate but very abrupt at the actual point of disconnect. This is the important feature, so it works just fine.

Peter

[Jetijs]

Ok, thanks Peter

[lighty]

I live in Latvia, that is not too far away
Got any links form mu-metal manufacturers in Germany?

I could check out the address of our supplier. I will let you know via PM.

[lighty]

As for collecting energy from the turn off of the circuit, the reed is "slow" to actuate but very abrupt at the actual point of disconnect. This is the important feature, so it works just fine.

I beg to differ. The turn-off time of reed switch is several orders of magnitude longer than with any semiconductor. Since the inductive collapse voltage amplitude is a directly dependent on the shortness of that time it is very important to reduce that time as much as possible. Actually I compared the results when using a relay or reed switch and MOSFET. With the same current passing through the coil and the same core saturation level the inductive collapse voltage controlled with MOSFET was about 15-20% higher in comparison with electromechanical interrupters. Now, if one is into recycling the energy of the inductive collapse then one should consider using the semiconductor switches because for the same amount of current one could get back much more energy out of a coil. Of course the suddenness of the collapse is depending on a hysteresis loop of a core etc.

[Peter Lindemann]

Clarification, Please....

I beg to differ. The turn-off time of reed switch is several orders of magnitude longer than with any semiconductor. Since the inductive collapse voltage amplitude is a directly dependent on the shortness of that time it is very important to reduce that time as much as possible. Actually I compared the results when using a relay or reed switch and MOSFET. With the same current passing through the coil and the same core saturation level the inductive collapse voltage controlled with MOSFET was about 15-20% higher in comparison with electromechanical interrupters. Now, if one is into recycling the energy of the inductive collapse then one should consider using the semiconductor switches because for the same amount of current one could get back much more energy out of a coil. Of course the suddenness of the collapse is depending on a hysteresis loop of a core etc.

Lighty,

In the tests you refer to above, are you comparing the turn off time of a MOSFET carrying current and a large relay contactor carrying current?

The little magnetic reeds cannot carry any current and I am only suggesting that they be used to TRIGGER an electronic switch, such as a transistor. And again, this suggestion is only to get Jetijs motor running initially. In order to maximize speed, power and electrical recovery, more precise methods, as you suggest, will be required. I'm just trying to help him get the motor running with what he has. Improvements can be added later.

Peter

[lighty]

The little magnetic reeds cannot carry any current and I am only suggesting that they be used to TRIGGER an electronic switch, such as a transistor.

Ahhh, now I understand correctly. Well in that case, yup, reed switch should me more than enough for the experimental purposes. I'm just not sure about the oscillation of the triggering signal and if any debouncing is needed, although I suppose if the trigger threshold od MOSFET is high enough that shouldn't represent any problem whatsoever.

Oh, and Peter, I do appreciate your efforts and patience!

[Peter Lindemann]

Reminder....in case you hadn't seen this

Ahhh, now I understand correctly. Well in that case, yup, reed switch should me more than enough for the experimental purposes. I'm just not sure about the oscillation of the triggering signal and if any debouncing is needed, although I suppose if the trigger threshold od MOSFET is high enough that shouldn't represent any problem whatsoever.

Oh, and Peter, I do appreciate your efforts and patience!

Lighty,

Here is a link to the basic schematic of the machine Jetijs is building:

Rotary Attraction Motor Update

You can see that the little magnetic reed is just connecting and disconnecting the voltage divider section of the circuit. Plus, when the reed shuts off, the resistor R2 is still connected from the emitter to the base of the transistor, so the transistor shuts off quickly.

The little reed switches don't bounce as much as the larger relays because the reed itself is magnetized. They just clamp and release.

I hope this helps.

Peter

[sykavy]

I was speaking with a friend about the electric recovery to the second battery. He said that the attraction motor has the advantage of using less electricity because if you tried to recover the spike from a normal electric motor you would probably blow the batery up.
The attraction motor also stays at the same level of input while the normal electric motors vary up and down making recovery very complicated.
Does this sound right?

[nali2001]

You can indeed pulse drive a normal big dc motor and recover like 80% and drive a second somewhat smaller motor from that, and so on(which is already o.u right there). But these motors normally do of course draw more under load. You can recover the back spike of nearly everything that is pulse driven, including transformers. Your battery won't really blow up since it is possible to transform the spike to lesser voltage.

Regards,
Steven

[Jetijs]

Peter,
recently I have been busy, because I have a job and can spare some time for the motor building only on the off work time. That is why I am progressing slowly, but I am getting there and nothing will stop me
In the mean time can you answer a question? So If I wind my startor coil from several parallel strands of wire, what is the difference between pulsing each of the strand with its own transistor and pulsing them all together with only one transistor, provided that the transistor can handle enough current? When I experimented with SSG circuits, I noticed, that I can get more RPM with two power coils if I pulse them with two transistors, each transistor for each coil. But when I used only one transistor and pulsed the both coils in parallel, I got only a little increase of RPM. Why is this so?
Thanks