3 wire proximity switch help

**JAZZCNC** · 05-10-2015

Originally Posted by mikem

JAZZCNC

I read what your saying as use two switches but conect them to the same input pin on the BOB like cropwell sugestead. Is that what your saying?

No I'm saying just use One switch. These switches sense a metal object for the trigger so just place trigger at each end using only one switch and one input.
Then set the limit Inputs for both ends to the same pin number. Mach doesn't care or even Know which switch tripped it just watches the designated input.

You can even Share the same Switch and one end trigger for Home function if you like by just setting Mach Home input for that axis to same pin number. Then turn off the Home SW option in General config so turns off Limits while it's homing and you don't get a limit trip. After homing Mach turns limits back on so your safe again.

Doing this means you only need 3 inputs for all axis including homing.

Edit: Doh didn't see Rob beat me to reply.

**mikem** · 05-10-2015

Jazz

That's exactly what I'm trying to do us 3 imputs for all axis. If I just use one swithh for the Y axis the switch is facing one way and picks up the metal object. What is going to trigger it going the other way if the switch isn't going to come in contact with the metal stop? How do I get to trigger it going the other way?
Mike

**Neale** · 05-10-2015

Make the switch point down, not sideways, and set the trigger pieces of metal just below it at each end of travel. It sounds as if this wouldn't give such accurate results but Jazz did some experiments a little while ago that showed this to work well.

**mikem** · 05-10-2015

Ok thanks make a lot of sence that way. I'll try it and see how it works.

Thanks Again

**JAZZCNC** · 05-10-2015

Originally Posted by Neale

Make the switch point down, not sideways, and set the trigger pieces of metal just below it at each end of travel. It sounds as if this wouldn't give such accurate results but Jazz did some experiments a little while ago that showed this to work well.

Yes sorry I didn't look closely at the way you had the switches pointed. Neal is correct it does work very well I use the round type switch like this all the time.
Also saves the switches getting smashed by riding over the target rather than into end stops.

Keep the sensing distance small has possible for best accurecy.

**mikem** · 06-10-2015

So why I got you I have another question. When I hook up on switch to the 5V on the BOB and to the imput lets say on the y it works.Then when I hook up the X and add another transistor to the 5v neither will work. just when it's a single resistor on the 5v do they work as soom as I add another nothing works.

Any thoughts?

**cropwell** · 06-10-2015

Are you powering up the BoB from the USB input or a separate power supply? The reason I ask is that USB supplies a limited current and you might not have enough power to work the BoB and more than 1 resistor. You may remember that I recommended that you did not use the USB port on the computer to power the BoB !

**cropwell** · 06-10-2015

Originally Posted by JAZZCNC

Also saves the switches getting smashed by riding over the target rather than into end stops.

.

Been there, done that

**mikem** · 06-10-2015

No I'm using a separate 5v PS. The lights don't light up when it makes contact either. But when I put the Blue wire on the 12v ps with the + it's lights up brite

**cropwell** · 06-10-2015

I think we have the problem !

The earth return paths are not connected. The blue wire from the sensor should be connected to the 0v (gnd) terminals on both power supplies and also (of course) to the 0v ground on the BoB. This is the most likely explanation of the symptoms.