Hi. Not sure if this is the correct topic to post this under, but I am using a hall sensor to measure a sine wave on a linear motor. I have several of these motors and several sensors that I need to make coordinate with one another to produce one sine signal. I have a sine wave, but no way to line up the waves perfectly from sensor to sensor. I am thinking that I need a second positioning signal in order to line up the other sine signals together as the rotor slides through, but I am not sure if there is an easier way to do this. I basically need to feed this signal into a variable frequency drive as if it was an encoder input, and our drive can take a sine input directly. I just need to get one wave out of all the sensors tied together along the line of linear motors. I know I probably didn't explain this very well so please ask if you need more information!

Thank You,
Joe

 

Hi Joe, can you explain your question a bit more, maybe a diagram for example, its a little hard to understand the situation and what you are trying to achieve.

 

Hi Joe, can you explain your question a bit more, maybe a diagram for example, its a little hard to understand the situation and what you are trying to achieve.

Ok. I will draw something up. Kind of figured I didn't explain it well...

 

 

I have several of these motors and several sensors that I need to make coordinate with one another to produce one sine signal.

What I believe you are looking to do is synchronize not two but multiple sine waves. That assumes same frequency and amplitudes which is not going to be easy. You want zero phase shift I assume and zero is not easy to obtain. There are devices to do it but they can be expensive. You may be able to sync two, then cascade that with additional sine waves but I am unsure how well that would work. I would start with a Google of "Synchronizing Sine Waves".

Ron

 

Well I don't know if this matters or not, but the motors and sensors are identical. Zero phase shift with some tolerance is my goal. I am wondering if converting it to a high resolution square wave would help. Like the one both.

 

Hi Joe, I think I see what you mean you sort of want the sensor outputs to overlap seamlessly?
I can't think of any electronics solution to this to be honest, I think the simplest solution would be mechanical, positioning each sensor using a screw thread adjustment and tune the signal.
That said you just need to position each sensor an integral number of magnet spacing for each other don't you?

 

Hi Joe, I think I see what you mean you sort of want the sensor outputs to overlap seamlessly?
I can't think of any electronics solution to this to be honest, I think the simplest solution would be mechanical, positioning each sensor using a screw thread adjustment and tune the signal.
That said you just need to position each sensor an integral number of magnet spacing for each other don't you?

Yes I want them to make one signal as it passes by multiple sensors. I guess if I center them perfectly on each motor then theoretically, it should line up perfectly.

 

Is the purpose of this device to synchronise the movement of the actuators or to produce the sine wave ? What is the final function of this device ? If we understand what you are trying to do it may help us to come up with a solution.

Les.

 

It seems to me that you'll want 2 sensors on each unit, spaced so that they're 90 mechanical degrees apart. Meaning that when one is at a peak, the other is at a zero crossing. Otherwise if you saw an output at the peak, and it went lower (which of course it must do) then you wouldn't know which way the unit had traveled. A single sensor only works as an encoder if you have reliable information of which way travel is occurring.

 

Precision magnetic encoder

• Resolution to 1µm, accuracy to ± 10μm
• Repeatability / Hysteresis to ±1 increment
• High-speed, real-time operation
• Non-contact and wear-free
• Highly immune to contamination by dirt and liquids
• Resists shock and vibration
• Incremental, absolute, or hybrid interfaces
• Low-profile tape and compact sensors
• Measurement lengths up to 48 m

https://www.balluff.com/local/mx/pr.../sensors/magnetic-linear-and-rotary-encoders/

 

I used and knew these as LVDT's?
Max.

 

I'm using these sensors to pick up the magnetic field from the magnets as they pass by, and since each magnet is polarized differently, it will give a sine wave as it goes through. The magnetic flux in these areas can reach up to 8,000G (0.8T). You can feed the drive directly with a sine and cosine wave for precision feedback as if it was an encoder. I have my sensors spaced 2.25 inches apart so that I achieve the 90 degree phase shift. I already have the two sinusoidal waves that I need, I just need to put multiple of them together in a line and so that they time correctly with one another as the magnets move from one motor to the next...