Limit switches PCB schematic verification.

[cncnoob]

Hi everyone.

Ok. Quickly to reply to a couple posts..



To Jonathan. I've changed my design a little to incorporate 24v [Please see attached].
I've been playing around in simulation with this, but when the switch goes LOW I'm still left with some residual voltage, will this still damage my card? I certainly don't want to risk blowing my card, or even worse my system!
I'm not entirely sure I have the right values here either, just used trial and error until I ended up with a stable circuit..
(I'm no electronics guru as you can probably tell!)

I am still getting roughly 800mV on the PP pin.. Will this be a problem, is there another way I can do this so I get an absolute 0v here?


Also missing caps etc here, any suggestions on values/configs?



To cropwell. I tried to insert a 3k on the 5v line, but the sim just plain didn't like it, (as the schematic in your link). It kept blowing out the opto..
In terms of PP PCI card, I have used these guys before, so know they are consistent. I don't mind paying a little more for something, if I know it will turn up, work and I don't have to worry about returns etc. But thank you for the thought, it's always good to know there are places that do hardware that cheap!
I'm still not sure if the one I posted up is suitable?! Could someone please kindly confirm this?



To MC. The POKEYS looks interesting, am I right in saying that this is a straight up micro controller? If I ran the opto from the return of the 24v to this and programmed a controller, would that mean I could run the 5v straight in to the PP card input, or would I still need to add a load between the micro and the input pin?
The reason I ask is that I have been recently working with 8/32bit micro controllers, but am a little unsure when it comes to PC hardware electronics. For example, I would know how to send serial via USB, but then wouldn't know how to get Mach3 to interpret it as a function.
But then maybe I would be complicating things if I went this route.
Unless I went the voltage to PP route, reading from the micro controller input?
I need more info on this, so will have another look around for more info also..




To C_Bubba. Totally understand the reasoning behind having everything in series.. But, I'm kind of looking to keep everything separate for expanding, chopping and changing later on.
Also I would like to use the full 9 limit functions in Mach 3 (IE ++X, --X, ++Y, --Y etc). I have got this right, they are the limits per axis? Or am I missing something else here too..
I can't plug in to my current controller with out voiding the warranty, this is why I'm going the DIY route. It'll be cheaper, more flexible and having a dedicated board for limits means I get to use more inputs instead of just using one input for everything.
I am new to this all, so please excuse me if I'm missing the obvious, I'm just experimenting and want to give this a go. Hopefully it'll pay off, and then I can look in to building my own fully fledged controller one day.. (Fingers crossed!)




To JAZZCNC. May be putting in some digi probes, tool changing, secondary homing etc at a later date, if I'm going to make this thing instead of buying one, I need all the help I can get!
(From the controller, and other people!)
Or maybe I just generally need help.. lol
I certainly would like to try this, and if it works I'll be happy that I have those options available for expansion later on, even if I don't actually ever use them.
Realistically I'm only looking for ten at the moment, 9 limits (3 of which are the homes) and 1 for a probe that I'm going to also DIY shortly (if/when I get this up and running safely..)






Thanks everyone for the feedback, hopefully I'll hear back from you soon so I can get this sorted and not have worry about hurting myself or my machine!

All the best!