Soleniod Driver - With Magnetic Proximity Sensor

Thread Starter

JPH85

Joined Mar 1, 2021
2
Hello -

I am working on a project where we are building an in-running BLDC motor from 12 individual coils. Where each coil - will possess its own driver and will be activated by its own proximity sensor (NJK-5001c or NJK-5002a). For this motor - speed and force are important. So for all intents and purposes I would like to find a driver which can hit the coils as fast and hard as possible. I understand that "fast" and "hard" are relative aspects - and that I am really limited by my power supply and the coils themselves. And that heat is also a trade-off as well. So for now - im just trying to find a good driver which can at least get me moving in the right direction in terms of Speed and Force.

The power supply I currently have on hand is an adjustable DC 30v - 5a.
The coil when measured with a LCR says 3.5ohms and 5.7mh.

The driver I currently have - For the most part just functions with the proximity switch. And produces almost no force at all. I can wave a PM in front of it - and the solenoid activates and that's about it. It consist of an n4007 a 100R a 100uf 35v and a TIP42C. I have read around and seen various designs - and read a thread on this forum called "hit and hold solenoid". However I am not very well versed in electronics nor its practice or theory. So I dont know if im looking in the right place or need to a design a completely different driver specifically for what I am after. Likewise - I have failed to adapt any of the solenoid drivers I have seen - to make use of the proximity sensor on my own. From what I have gathered - I need to use faster switching components - like a mostfet over the BJT - and fast recovery diodes. As well put one diode in reverse/parallel to kill the back emf? The speeds I am after are around 5-25ms. Depending on the force I can generate. I am also hoping their is enough downtime in between activation - to potentially generate more force for my coil? If anyone has any designs they could assist with or can point me in the right direction I would greatly appreciated. I also apologize in advance if I asked for one thing and explained something completely different.
 

shortbus

Joined Sep 30, 2009
8,806
I am working on a project where we are building an in-running BLDC motor from 12 individual coils. Where each coil - will possess its own driver and will be activated by its own proximity sensor
Can I ask why? I don't understand a reason to make a BLDC motor more complicated instead of less complicated?
 

Thread Starter

JPH85

Joined Mar 1, 2021
2
Thank you for the replies MaxHeadRoom and ShortBus.

MaxHeadRoom -

I think its a in-runner. The picture below is almost identical to what I am after. Just my project is going to be much larger. I am mounting the coils around the perimeter of a 20" Diameter plexiglass plate. The PMs will be mounted around the perimeter of a 16" Diameter plexiglass plate. Giving me about 2" of length for the coils on either side of the 16" Dia Plate. The 16" DIA plate will rotate - the 20" plate with the coils will not.


1615055151229.png

Shortbus -

Its for a specific project - which more then likely will need constant adaptation until I get it to where I need it to be. Like changing the diameter of the rotating plate - changing the size of the coils - removing or adding more coils etc. So I am trying to keep things modular so to speak. So its easier to work with/plug and play. This also makes it easier for me when I need to run force calculations across the set up. The focus will be lightweight - speed over surface area. With relatively low torque. By relative - Im still focused on F=Ma and F=IlBsinθ . I just need the majority of force/torque - to be spent on rotational speed. So trying to find a driver which can potentially enhance the force generated by the coil so I can get more speed- while operating at a high frequency with the sensor.

The surface area is important - because their will be multiple BLDC motors nested ontop of another. 16", 12", 8". Using a system designed to leverage and overdrive relative velocity.Yes - large motors can accomplish the end result in terms of speed (potentially). But weight is a critical factor in this design. Which is why I ditched the stator. And am starting with Air cores and plexiglass. Doing my best to avoid a tanget but still give enough information to help paint a picture. Let me know if this helps. The why part will just open pandora's box...
 

MisterBill2

Joined Jan 23, 2018
9,267
There are already frameless motor parts available and probably they would cost less if you need to create a few of these. Probably the parts for the application are fairly standard with some motor manufacturers. Then only the driver electronics need to be created,. Much easier to be consistent and a lot cheaper as well.
 

shortbus

Joined Sep 30, 2009
8,806
Let me know if this helps. The why part will just open pandora's box...
.
Not really. BLCD motors are usually 3phases, so trying to drive them coil by coil makes no sense, at least not to me. And so far your not showing any way of commutating the solenoids with rotor position. Which in the beginning was done with Hall sensors or even opto interrupters and now days is done with some form of electronic sensing.

And the Pandora's Box comment is very telling. Along with some of the rest of your description, but will hold my comments to a later date.
 

MaxHeadRoom

Joined Jul 18, 2013
23,619
There is no (or very little) physical difference between BLDC and PM AC 3ph.
Just the method of commutation, the BLDC has only two winding energized at any one time, as opposed to full 3ph on the AC version.
 
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