Prox switch target

[saiber]

We use a prox switch to detect rotary motion by mounting targets on the shaft of machinery (industrial - dirty). The target is typically a sprocket (4-6"DIA). The teeth moving by the stationary prox create pulses & we do the logic in the PLC. Does anyone out there know of a pre-fab target that can be purchased (more to the specs listed in most prox application sheets- target surface area .5w"x.5d"x.5"h spaced 1&quot? A sprocket tooth comes to a point and does not leave much room for misalignment.

 

[jacekd]

How about using incremental hollow shaft encoder ?

 

[saiber]

I don’t think it would last. The application is both mechanically and environmentally demanding. Hot (>150F), covered with grease & dirt, prone to being mechanically abused. This is an industrial application.

 

[buzzp]

You might consider a diameter with magnets mounted on it to give a better target and use a hall effect sensor for detection. This is proven technology for industrial applications. I believe you are using an inductive or capacitive type of prox switch. Cost is very comparable (at least for the sensor part) to an inductive or capacitive type of switch.

 

[nornrich]

Saiber,

Does the the prox switch have to be mounted perpendicular to the shaft? We used the same application in equipment we designed and mounted the prox switch parallel to the shaft. We then used a round piece of sheet steel welded to a shaft collar. In the sheet steel are drilled holes that are detected by the prox switch. Depending on the size limitations you can vary the number and size of the holes.

Rich....

Richard Nornhold, PE
nornrich@redrose.net

 

[plcsavvy]

This sounds like the perfect application for a programmable cam switch. Might I suggest using the Electro Cam brand of products. The electro cam unit has a controller that is attached via cable to a resolver. The resolver is normally belt driven from the out put shaft of the machine. the controller provides outputs that are dependent upon the mechanical position of the output shaft of the machine.
the putputs are programmable. for example, if you need an output to fire a cylinder from 120-150 degress you can program any output to do so. The output is then used as an input to a PLC or embedded controller.

best regards, PLCSAVVY

 

[bprinner]

Contact a company called ELECTRO-CAM in Roscoe Ill. They specialize in rotory sensors of all kinds.

 

[saiber]

Thanks nornrich. Thats a good idea. I may not be able to fit it in on this application but I will keep in in mind. plcsavvy and bprinner, I' check out Electo Cam but I was looking for something low tech (Cheap, minimum moving parts, minimum nuts & screws. Ind prox (have installed base)with nornrich's idea may be a better fit than the sprocket.

 

[superbab]

You could have a local machine shop make you a special sprocket with larger arced teeth so that they will be equal distance from the prox while turning. You could have the inner collor the same dimension as the shaft and the outer dimension the same as the spocket; no great modifications required. It should cost only slightly more than the sproket that you are using now.

 

[buzzp]

Square tooth sprockets are also readily available.

 

[CAdkins]

This is probably late in the game, but check these:

http://www.redlion.net/Products/Groups/SensingGears/SensingGears/Docs/11003.pdf

Redlion makes several gear sets to bolt on for this application. They are not the only supplier, but they do have several to chose from.

Good Luck!