Which Type of Limit Switch

[manofgresley]

I f i read it right, this unit you recommend is fixed on the mill bed and a peice of metal is attached to each axis, the metal inserts between the 2 posts of the switch and makes the contact?

Which is tricky on a mill, also the mill itself is a big chunk of iron so mounting proximity switches so they're not affected isn't so easy. Optical sensors as shown in the link on Eddie's post in suitably sealed boxes are a neater solution. A suitable sensor is this one: http://uk.farnell.com/omron-electron...ive/dp/1348961

[Clive S]

I f i read it right, this unit you recommend is fixed on the mill bed and a peice of metal is attached to each axis, the metal inserts between the 2 posts of the switch and makes the contact?

Yes its an optical switch that is to say an invisible beam of light it being shone across the gap in the sensor and then when use pass a piece of dark plastic or metal into the gap it breaks the beam and triggers. ..Clive

[manofgresley]

Many thanks for the explanation, this switch seems rather small, the spec sheet says it has a gap of only 3 mm, therefore i would need a piece of metal less than 3 mm thick to go through it, would this not be a bit flimsy for a robust milling machine? and also would this switch be ok powered by my ZP5A Breakout Board, which only gives out 5 volts? and does it wire directly to the BoB?

Ray

Yes its an optical switch that is to say an invisible beam of light it being shone across the gap in the sensor and then when use pass a piece of dark plastic or metal into the gap it breaks the beam and triggers. ..Clive

[EddyCurrent]

These are the ones I used;
http://www.ebay.co.uk/itm/2pcs-SN04-...item5d38dcb5f5
Albeit on a router, they work well and are very repeatable. Because they are 3 wire NPN you can power them from a 24v supply but still connect the output to your 5v bob input where they either leave it open (high) or short it to ground (low).
The drawing here shows how they are connected; (bottom left corner of drawing)
http://www.mycncuk.com/threads/6565-...7622#post57622

[Clive S]

Eddy beat me to it but there are these as well and bit cheaper. I use this sort of thing on my router and will be fitting them to the mill. You do have to watch out for swarfe but if they are mounted under the bed or have a cover over I don't see a problem.

Normally open http://www.ebay.co.uk/itm/TL-Q5MC2-I...item1c41faa863 or

http://www.ebay.co.uk/itm/New-LJ12A3...item53ffd022e5

Normally closed:- http://www.ebay.co.uk/itm/DC-6-36V-N...item417755e4ae and

http://www.ebay.co.uk/itm/4mm-Tubula...item43bbcedff7 Also
this :- http://www.ebay.co.uk/itm/DC-10-30V-...item43bbcddc3b ..Clive

[manofgresley]

Many thanks, I like the look of this one,http://www.ebay.co.uk/itm/New-LJ12A3...item53ffd022e5 i can easily fit these to my machine, my Bob is only 5 volt so do i need a relay? and how do i wire a 3 wire switch, can you do me a schematic, i'm not an electrician.

RayQUOTE=Clive S;60092]Eddy beat me to it but there are these as well and bit cheaper. I use this sort of thing on my router and will be fitting them to the mill. You do have to watch out for swarfe but if they are mounted under the bed or have a cover over I don't see a problem.

Normally open http://www.ebay.co.uk/itm/TL-Q5MC2-I...item1c41faa863 or

http://www.ebay.co.uk/itm/New-LJ12A3...item53ffd022e5

Normally closed:- http://www.ebay.co.uk/itm/DC-6-36V-N...item417755e4ae and

http://www.ebay.co.uk/itm/4mm-Tubula...item43bbcedff7 Also
this :- http://www.ebay.co.uk/itm/DC-10-30V-...item43bbcddc3b ..Clive[/QUOTE]

[irving2008]

Wiring of these was discussed at length on many threads. Here is a schematic I did for one such thread showing all possible variants...
You don't need a relay, its overkill and unnecessary if your BOB has opto-isolated inputs.
.

[manofgresley]

These are the ones I used;
http://www.ebay.co.uk/itm/2pcs-SN04-...item5d38dcb5f5
Albeit on a router, they work well and are very repeatable. Because they are 3 wire NPN you can power them from a 24v supply but still connect the output to your 5v bob input where they either leave it open (high) or short it to ground (low).
The drawing here shows how they are connected; (bottom left corner of drawing)
http://www.mycncuk.com/threads/6565-...7622#post57622

I only have a 5 volt supply will this work?

Ray

[Clive S]

I only have a 5 volt supply will this work?

Ray

You really need a 12V or 24V power supply to work but they can still be connected to your BOB, power supplies are not expensive. ..Clive

[manofgresley]

You really need a 12V or 24V power supply to work but they can still be connected to your BOB, power supplies are not expensive. ..Clive

I do have both power supplies in my CNC cabinet, so can i refresh -
I need 12 to 24 vdc proximity switches, NPN, N.C. all i need know is a scheme / Wiring diagram, can you help?

Ray