Travel limit switch placement for rotary turntable 1

[ewans]

Hello all,
Looking for some help with a problem that has me stumped...

I've got a rotary turntable that travels ±200° and I'm trying to locate inductive proximity switches and targets around the circumference of the turntable to provide CW and CCW limit signals. Ideally, I would like to provide 2 discrete signals, one for CW limit and one for CCW limit. However, it would be acceptable to provide a single output signal to indicate a limit, but not know which limit. I would like to use 2 or 3 proximity switches and some combination of targets, and would like to avoid requiring any software logic to evaluate the outputs.

So far, I've tried countless combinations of switch and target placements, but have not been able to find a configuration that works. Everything I've tried will provide an output signal at the correct limit when travelling in one direction, but with the direction reversed, it will provide a second incorrect output. In other words, it seems that I would need to include the direction of rotation in some form of logic circuit (i.e. "look only at switch A when travelling CW, and look only at switch B when travelling CCW").

Any chance I'm missing something obvious? Any help is appreciated.

Regards,
Ewan

 

[Ron]

Why not just use mechanical limit switches instead of electronic. I realize that's retro, but it works.

Are the targets mounted on the shaft or the turntable?

 

[zekeman]

"Put the targets on a disc that rotates at half the turntable speed. "

What happens at 360 deg of turntable? Doesn't see 0 degrees.

 

[MikeHalloran]

Turntable rotates 400 degrees.
Half-speed disc rotates 200 degrees.


Mike Halloran
Pembroke Pines, FL, USA

 

[zekeman]

Turntable starts at 0 , gear reads 0. Turntable moves 360, gear moves 180 and loses its 0 position.

 

[ewans]

Morning all,
Many thanks for your replies... much appreciated.

Regards,
Ewan

 

[tr1ntx]

Ewan,

Yeah it was too close to lunch time and I was rushing. I mirrored the CCW sketch to the CW case and forgot to consider the switches not shown. I realized it during lunch, but then I got real busy with a production problem and didn't have a chance to say Oops!

A half-speed disc or putting switches at different radii would work, but I think it can work with switches at the OD. Let me ponder.