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Motor controll circut

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Jack H

New Member
Hello All,
I have a question, and would be very gratefull if some one could help. I am currently working on a new type of DC electric motor, the current version of this motor uses a set of motor cycle points to turn the coils on/off, causing alot of drag and arcing across the points. :cry: Was wondering if the MOSFET circut that I have drawn up will work instead of the points. And if so could some one tell me what the R1 and R2 resistence should be. Or if the circut needs totally changed. :?:

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Klaus

New Member
Jack H said:
Hello All,
I have a question, and would be very gratefull if some one could help. I am currently working on a new type of DC electric motor, the current version of this motor uses a set of motor cycle points to turn the coils on/off, causing alot of drag and arcing across the points. :cry: Was wondering if the MOSFET circut that I have drawn up will work instead of the points. And if so could some one tell me what the R1 and R2 resistence should be. Or if the circut needs totally changed. :?:

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Can you explain what exactly you mean by "turning the coils on/off"?
Are you trying to replace the communtator & brushes with some other method of switching? Or, are trying to turn the power to the motor on/off?
Your circuit diagram makes no sense to me, what triggers the opto switch?

The more detail you provide the better your chances of a reply here. :wink:
Klaus
 

Jack H

New Member
Motor control circut

Klaus,
Sorry about the confusion, I guess I have been working on this project so long, it's starting to fog my mind.

This is a totally new and different kind of dc motor. The armiture or rotor has no windings on it what so ever. The motor has no communtator & brushes. The coils are used as field coils and totally power the motor. At present, I am powering the coils on/off by using a set of motorcycle points (open/close). A small cam on the shaft of the motor operates the points.

Now, I would like to replace the motorcycle points with electronic switching. I have built a small disk that is mounted on the motor shaft, this disk will have two notches cut into it that the opto sencer will sence. When the opto sencer trigers on/off it will also triger the mosfet on/off to power the coils. The coils will need to be powered two times per rev of the motor.

The diagram I included with this post was located on the web, it is being used to operate another dc motor(ADAM's Motor) that is similer to mine.
However my motor uses a totally different type of coils. The amp load is different. An there was no parts list or discription included with this drawing.

I just need to know the voltage the mosfet needs at the gate to open it up and how do I get there from 36 vdc power. Also need to know exactly how to hook up the opto sencer.

Hope this helps, Thanks for your help. Later,,,Jack

I am totally NEW at electronics
 

GraveYard_Killer

New Member
based from h21a1 datasheet, emitter needs 1.7V and eats maximum current of 50mA.
lets say, I=15mA
R1=(36-1.7)/15mA=2286.67 ohms
 

gerty

Member
If the motor stops at a point between the 2 notches power won't pass to the coils, how are you going to start the motor :?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Re: Motor control circut

Jack H said:
This is a totally new and different kind of dc motor. The armiture or rotor has no windings on it what so ever. The motor has no communtator & brushes. The coils are used as field coils and totally power the motor. At present, I am powering the coils on/off by using a set of motorcycle points (open/close). A small cam on the shaft of the motor operates the points.
It sounds similar to a conventional 'DC brushless motor', these are common place, and have been for years - the first I ever heard of were used in top end reel to reel tape recorders back in the 1960's.

Most VCR's have at least two of them, the drum and capstan motors.

Presumably like yours, the rotor is a magnet, and the coils stay still, and the different coils are switched ON and OFF. The actual sensing is done by a number of hall-effect sensors, which detect the position of the rotor magnet itself, switching the coils in the correct sequence through a custom IC.
 

Jack H

New Member
Grave_Killer,
Thanks for the info on the voltage. I have looked at the data sheet and still can't find it. Now what size resister do I use to cut the voltage down from 36vdc to 1.7vdc? Also the MOSFET APT10078BLL data sheet I think is telling me that the gate will take up to 30 v plus or minus. How do I set up the resistance along with the collector/emitter from the opto sencer to send the correct voltage to the gate of the mosfet.

gerty,
The motor is just in test stages. The current motor has only one set of fields and coils. Pull on the rotor is just over half a cycle, resulting in a dead spot. The final motor will have at least two sets of fields and field coils. Each set pulls on the rotor just over half a sycle. Resulting in no dead spot. Also this will more than double the power output, due to the rotor having no coast time.


Nigel Goodwin,
This motor is not like the drum and capstan motor in any way. This is a totally new consept for dc power generation. The rotor is not magnetized or does it contain any magnets.

 

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Klaus

New Member
Jack H said:
This is a totally new consept for dc power generation. The rotor is not magnetized or does it contain any magnets.

Jack, your last sentence (quoted above) makes for a very poor motor :wink:
The very principle of electric motors involves the attraction and repulsion of magnetic force, wether that force is from permanent or electro magnets.
So, if your rotor does not have any kind of magnetization, why should it rotate at all? Now, if your rotor is made of conducting material and it is placed within a powerful magnetic fied it will have eddy currents induced which in turn set up their own magnetic field, negating your statement above :wink:
Klaus
 

Jack H

New Member
Klaus,
The rotor is not made of a conductive material. With todays tech there are now materials that are none conductive but very much atracted to a magnetic field and can out perform meterials that are used in most motors today. There are NO eddy currents in this motor.

Also the main reason I came to this board was not to discuss how good or bad my motor was. I for some reason thought that I might find an electronics expert that could help me design a simple circut to power the coils with an opto sencer electronically. And just maybe I could get rid of the old used motorcycle points. Where are all the experts?

Later,,,,Jack
 
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