Magnetic multipole Strips for linear encoder

[Nakitxu]

Hi!

I'm looking for any cheaper linear encoder system.

My first idea was try to use the capacitive sensor or any these chinese Digital Vernier Calipers, (I just have bought one of 6 inch for 8 euros with free shiping), but...I need al least 500mm long and the calipers with such long exists, but are very expensive compared with the 6 inch long, so... I decide go for other way: the Austria Micro Systems linear magnetic encoder chip: AS5306

This chip detects the position of itself relative at the magnetic field. You can use any magnetic field with poles separated 4mm.

They shell Magnetic Multipole Strips, than contains these magnetics poles: http://www.dextermag.com/Multipole-Press-Release

I have found this strips for sale a good price (3$ for 300mm) in the Makerbot site, but... ths ship cost for Spain is very prohibitive:   

http://store.makerbot.com/magentic-adhesive-strip.html

Somebody has experience with this chip and this Strips? (or with another strips or inventions)
Where do you buy the strips?

I think if would be possible use a cassete or video tape with a trend recorded as magnetic strip for these chip... I dont know... maybe the chip requires a lot more strength of magnetic field.

[bradleytron]

I'm not clear on the details other than your desire being to measure/encode linear displacement. As an alternative to what you are suggesting, have you looked into PSDs (position sensing detectors)?

B

[Nakitxu]

I'm not clear on the details other than your desire being to measure/encode linear displacement.

I am just researching possibilities.
I want to build a 3 axes coordinate system for any projects I have on main. I dont want to use stepper motors, I want to use closed loop motor control with linear encoder feedback, but dont want very expensive parts, the whole goal its the low price.

I could make the invention with stepper motors, or rotary encoders in the motor axis but... this is not the idea.
Just want to find a inexpensive way to measure linear distances with precision for use as linear encoder

As an alternative to what you are suggesting, have you looked into PSDs (position sensing detectors)?

I will make a try with this search Thanks!

[Gall]

It is very easy to make high precision CAPACITIVE linear encoder (like cheap Chinese calipers). The strips may be etched on PCBs. Both the long strip and the sensor are multipole but with different distances between poles. This allows for 1/1000 inch precision or better.

[RobB]

Probably of no use as a supplier due to freight but maybe do a search for the same product closer to home.
Just be careful though the cheap chinese scales do not slide freely and may be too tight for low power drives

http://www.machineryhouse.com.au/Remote-Scales

[Gall]

Just be careful though the cheap chinese scales do not slide freely and may be too tight for low power drives

I once bought a caliper which was not even STRAIGHT.

[bradleytron]

I'm not clear on the details other than your desire being to measure/encode linear displacement.

I am just researching possibilities.
I want to build a 3 axes coordinate system for any projects I have on main. I dont want to use stepper motors, I want to use closed loop motor control with linear encoder feedback, but dont want very expensive parts, the whole goal its the low price.

I could make the invention with stepper motors, or rotary encoders in the motor axis but... this is not the idea.
Just want to find a inexpensive way to measure linear distances with precision for use as linear encoder

As an alternative to what you are suggesting, have you looked into PSDs (position sensing detectors)?

I will make a try with this search Thanks!

I was thinking along the lines of a PSD chip to do triangulation with a fixed laser diode, tinny mirror mounted on the moving parts... you can get very good resolution, say approx. 10 um or so. You would also need a small microcontroller to handle the calculation. You can check out http://www.sitek.se/, they provide a very thourough handbook. So, depending on your needs, resolution, accuracy and so on, you may find this to be a better alternative to the magnetic sensor.

B

[Nakitxu]

I was thinking along the lines of a PSD chip to do triangulation with a fixed laser diode, tinny mirror mounted on the moving parts... you can get very good resolution, say approx. 10 um or so.

Yes, I will study this, but... this can be a good option just if the environment of the machine is clean.
If I use the system as a PCB router o a milling machine... the dust and residual parts of the work maybe can put the laser reflection of the mirrors off the map.

[jeroen74]

Both the long strip and the sensor are multipole but with different distances between poles.

Likely n and n-1 poles over the entire length of the strip. The vernier principle.

[Gall]

Both the long strip and the sensor are multipole but with different distances between poles.

Likely n and n-1 poles over the entire length of the strip. The vernier principle.

Exactly.