Proximity switches or limit switches

**chillybo** · 08-12-2019

Hi everyone.
I'm at the stage of my build where I am about to buy electrical items. Could anyone cast any light on the differences between proximity switches and limit switches? Where would one be chosen over the other, advantages and recommendations.
My design is s 4 foot by 2 foot gantry style router made from aluminium extrusion.
Regards Chris.

**cropwell** · 08-12-2019

A proximity switch is a type of switch. A limit switch is a designated use of a switch. Limit and Home switches can be either electronic, like a proximity switch or mechanical, like a microswitch.

My personal preference is for Homing using proximity switches and Limits using microswitches.

**chillybo** · 08-12-2019

Thank's, cropwell so you have separate switches for homing and limits? From what I've gathered you can use the limit switches also as home switches (the home command initiates the desired directions of each axis). Is your design based on increasing safety / reducing risk of damage to the machine? As in the limit switches are placed slightly beyond the position of the home switches.

**cropwell** · 08-12-2019

I think design is a bit of a strong term to apply to my machine. I bought it from a company in Devon!. It came with proximity switches to act as homing reference only. These were mounted axially and I found it too easy to jog into them and crush them. So I went mad and put X++, X--, Y++, Y-- and Z++ homes and limits mounted so they operated by the axis traversing the switch. At the moment I have only one set on each axis as I had a wiring fault and disabled them temporarily (about a year ago!!)

**JAZZCNC** · 08-12-2019

Originally Posted by chillybo

Thank's, cropwell so you have separate switches for homing and limits? From what I've gathered you can use the limit switches also as home switches (the home command initiates the desired directions of each axis). Is your design based on increasing safety / reducing risk of damage to the machine? As in the limit switches are placed slightly beyond the position of the home switches.

The main advantage of using separate Limit switches is that you are protected while Homing. When the switches are shared for both Homing and limits then Limits are Ignored While Homing so it's not quite as safe.
That Said the advantages of using Shared switches, Esp if you use Single switch that travels with axis and searches for Targets at each end of travel is much simpler wiring with less chance of wiring errors, Also lower costs.

Regards which switch type to use then it's a personal choice. My personal preference is the Proximity switch because they are accurate and cheap. Also simple to mount.and don't have some of the issues mechanical switches can have.

**cropwell** · 08-12-2019

Originally Posted by JAZZCNC

That Said the advantages of using Shared switches, Esp if you use Single switch that travels with axis and searches for Targets at each end of travel is much simpler wiring with less chance of wiring errors, Also lower costs.

AND I would add, less to go wrong over time.

**chillybo** · 09-12-2019

Ah right, so would this be a proximity switch that could be mounted midway between say a gantry side. So its a single switch that detects a metalic reference point as it travels to the side of it at the ends of each axis. Or is there also a mechanical switch that could do this?
I like this idea it makes a lot of sense.

**chillybo** · 09-12-2019

Thanks for this Jazz this makes a lot of sense and gives more flexibility of where to locate the proximity switch on my machine.

**JAZZCNC** · 10-12-2019

Originally Posted by chillybo

Ah right, so would this be a proximity switch that could be mounted midway between say a gantry side. So its a single switch that detects a metalic reference point as it travels to the side of it at the ends of each axis. Or is there also a mechanical switch that could do this?
I like this idea it makes a lot of sense.

You can use the same approach with simple mechanical switches but they tend to slide over a ramped trigger plate to prevent damage to switch. Or you can buy Lever type mechanical switches with end stop that flicks the lever.
Proximity switches are my preferred switch type because they are none contact cheap and simple to use and fit.

**chillybo** · 11-12-2019

I will probably use proximity switches for homing and mechanical switches for limits just to add another layer of protection. Im not sure if I should buy normally open or normally closed proximity switches. My controller is the CSIO IPM and I'm using Mach 3. If I set the limit input to accept a normally closed circuit and the home / proximity switches to normally open on a different input to the controller would this work?
Thanks in advance...