Help me design an approximate sensor

[year]

I want to design the system as follows.
Please give me the idea.

1. There are rings on the shaft.

the ring is made by plastic and the shaft is steel.

2. user will operate up and down the ring

I want to check the position the ring by very very low cost self made sensor.

total rings are 10 or over.

But environment is very dusy so I can not light sensor.
and also the ring's material could be changable....

Does anyone have th idea for this ?

Help me

 

[rikie_rizza]

Approximate sensor

If you give a picture of the system that you are trying to build, may be it would be clearer.

Does the ring movement consistent? If it so, you can use an on off switch for detection. Do you need the distance measurement to be linear? If so, try ultra sound its cheap but not so easy to construct.

 

[penrico]

Re: Approximate sensor

Maybe hall efect sensor?. When you move the shaft, and cross steel and then plastic, the magnetic field will change.

 

[year]

Approximate sensor

This is the drawing ...
Please check it everybody.

 

[kender]

Approximate sensor

Do you need to sense the position of the ring (i.e. 37% of the length from the right)?
Do you need only to detect that the ring is in an end-positions?

 

[year]

Approximate sensor

I want to check the each position of rings.
Because the operation will be occured randomly.
Thanks a lot.

 

[FvM]

Re: Approximate sensor

Would be probably better solved by designing the sensor function into the construction from the start rather than supplementig it later, as it seems to be the case now. Some material choices or form factors may be adapted to the measurement requírements then. Integrating the measurement in the shaft is one option.

Generally, if optical sensing is regarded unsuitable, a capacitive proximity switch would be the next obvious solution for plastic objects, apart from ultrasonic or mechanical feelers.