Making a system with mobile electrical contacts

[_maxim_]

Hi all,
want to realize a system for a PCB which holds a solenoid coil moving in a vertical axis long about 600 mm. The coil must get electric contact only in some predefined positions so that, for a given quote, the coil connects to a different LC circuit for having different resonant frequency (infact, the resonance frequency depends from the height).

One problem is the space available: the PCB is 30 mm, but the space where it must move along the vertical is within 40 mm. Everything (PCB, contacts or/and cables) must fit in 40 mm

I though to a sort of creeping contacts but it looks impracticable with my knowledge.

Do you have any suggestion for that?

 

[berkeman]

Can you Upload a sketch? I'm having trouble picturing your setup and the constraints. Thanks

 

[berkeman]

Also, is this related to your previous thread?

https://www.physicsforums.com/threads/moving-a-solenoid-coil-in-a-strong-magnetic-field.939043/

 

[_maxim_]

Can you Upload a sketch? I'm having trouble picturing your setup and the constraints. Thanks

You're perfectly right and I am sorry for not having provided more details to my request. Please, let me find a way to sit down in front of my PC and I will try to draw a picture describing the needs.

 

[_maxim_]

Also, is this related to your previous thread?

https://www.physicsforums.com/threads/moving-a-solenoid-coil-in-a-strong-magnetic-field.939043/

Yes, sure : this i a thread of mine too :-)

There I have found a lot of interesting ideas to move mechanically the PCB, now I am point the attention particularly to the electric contact aspect when it moves along the axis.
Maxim

 

[berkeman]

Diagram needed...

 

[_maxim_]

This is a view of the chip supporting the coil, dimensions about 30 x 20 mm.

This is the rear view of the CHIP where a Hall sensor is also visible

The rectalgular boxes in both sides are for making the solenoid coil in contact with differernt RF circuit filters.
Is it enough for explaning the project?
I am sorry but I am not a cad designer... I am old and I have more confidence with paper and pen.

Thank you
Mx

 

[davenn]

The rectalgular boxes in both sides are for making the solenoid coil in contact with differernt RF circuit filters.
Is it enough for explaning the project?

not really

I am sorry but I am not a cad designer... I am old and I have more confidence with paper and pen.

so are you able to draw it, take a photo or so and upload the photos. Do you know how to do that ?

 

[CWatters]

We also need to know if this is just for a short experiment or long term use? For example sliding contacts might work but will wear out eventually. What sort of signal is going to/from the coil? Sliding contacts can produce electrical noise that might cause a problem if you are trying to measure a small signal.

Could you use IR light to send data to the moving coil or do you also have to send power? Could you put a battery or super capacitor next to the coil that moves with it? Charge the battery when machine isn't being used?

 

[Droidriven]

View attachment 223185 View attachment 223187
This is a view of the chip supporting the coil, dimensions about 30 x 20 mm.

This is the rear view of the CHIP where a Hall sensor is also visible

View attachment 223192
The rectalgular boxes in both sides are for making the solenoid coil in contact with differernt RF circuit filters.
Is it enough for explaning the project?
I am sorry but I am not a cad designer... I am old and I have more confidence with paper and pen.

Thank you
Mx

I'm far from an expert in any area involved in your project, but I can visualize your purpose.

To eliminate wear and tear that typically comes with moving parts, some form of wireless power/data transfer seems like it would help, then, for the motion and path of the solenoid, maybe some way of suspending the solenoid in its path in such a manner that it doesn't contact anything along its path, possibly some form of magnetically controlled field or maybe some kind of enclosed casing with the solenoid suspended inside in a liquid or gel that it can move freely through, the enclosure would have to encase the entire pathway of the solenoid.Again, I'm not an expert. These aren't technical design suggestions, more like conceptual ideas.

 

[_maxim_]

We also need to know if this is just for a short experiment or long term use? For example sliding contacts might work but will wear out eventually. What sort of signal is going to/from the coil? Sliding contacts can produce electrical noise that might cause a problem if you are trying to measure a small signal.

Thank you for your questions, I will try to be as more detailed as possible.

More details on microcoil here https://en.m.wikipedia.org/wiki/Microcoil

The application is for a long-term use, it is a device for reading RF signals from a chemical liquid sample moved into a magnetic field at fixed values.
The entities of currents is negligible in the sens that this class of application is quite similar to signals in MRI/NMR, where voltages amplitudes are in the range of nano/microvolt. The main purpose is to establish an electric contact for the solenoid in a given position where the magnetic field is known (that's why a Hall Sensor is present in other side of the PCB).
Let say 3 - 5 vertical positions (so 3 - 5 different resonant RLC circuits to be connected to the solenoid) are enough.

Could you use IR light to send data to the moving coil or do you also have to send power?

No, the signal pathway must be an RLC circuit as for an antenna.

Could you put a battery or super capacitor next to the coil that moves with it? Charge the battery when machine isn't being used?

No, the movement must be realized and contained inside the cylinder shield which is inserted in the magnet. Length and diameter are also fixed.

 

[_maxim_]

To eliminate wear and tear that typically comes with moving parts, some form of wireless power/data transfer seems like it would help, then, for the motion and path of the solenoid, maybe some way of suspending the solenoid in its path in such a manner that it doesn't contact anything along its path, possibly some form of magnetically controlled field or maybe some kind of enclosed casing with the solenoid suspended inside in a liquid or gel that it can move freely through, the enclosure would have to encase the entire pathway of the solenoid.

Thank you for your suggestion, but unfortunately the signal captured by the coil is really sensitive to any RF noise and the resonant frequency is in the range of 600 MHz to 10 MHz (depending from the position), so I guess the only hope to get it out from the probe is by a solid RF connection.

 

[Rive]

Thank you for your suggestion, but unfortunately the signal captured by the coil is really sensitive to any RF noise and the resonant frequency is in the range of 600 MHz to 10 MHz (depending from the position), so I guess the only hope to get it out from the probe is by a solid RF connection.

Quite difficult range of frequency. You might find some useful ideas in books about RF tuner circuits - but in general, this range is not really friendly with contacts. Instead of breaking up the resonant part with contacts, maybe you could shrink the whole resonant 'antenna' into that small PCB, and tune it with a varicap? Then you could solve the moving part with a simple flex-PCB.

 

[CWatters]

You won't be able to send nV or uV signals any distance or through wiping contacts without picking up a lot of noise. I think you need to be doing some processing/data capture on the moving board itself and transmit digital data from the board.

What do you plan to connect the coil to at the moment? Some sort of amplifier and DAC?

Any amplification should be done as close to the source as possible. It's why the best place for something like TV aerial signal amp is at the mast head.