Wiring 24v NPN Proximity Switch to 5v BOB - Why does'nt it work

[cropwell]

I think there will be an increasing delay put in to the circuit the more you connect.

Apart from the inductive sensing circuit, I see no capacitative or inductive components that will introduce any time elements into the switching circuit. Sorry for the delay in replying

[Clive S]

Apart from the inductive sensing circuit, I see no capacitative or inductive components that will introduce any time elements into the switching circuit. Sorry for the delay in replying

I was looking through this- http://www.ab.com/en/epub/catalogs/1...23/Wiring.html

It states "response time is equal to the response time of the first sensor plus the sum of the turn on times of the others. "

But all this has been killed to death many times. Can't beat having each sensor on its own pin.

[cropwell]

I was looking through this- http://www.ab.com/en/epub/catalogs/1...23/Wiring.html

It states "response time is equal to the response time of the first sensor plus the sum of the turn on times of the others. "

But all this has been killed to death many times. Can't beat having each sensor on its own pin.

This only seems to apply for two wire sensors in series. Three wire sensors in parallel won't be affected. Phew: our 'homes' are secure, we can all sleep safely in our machine beds this afternoon.



Rob

[Boyan Silyavski]

Ok. Now that io have you here :-) , i have another quick question . If BOB has transformer that powers limit switches and at the same time spindle speed output, and you connect a couple of limit switches in series and find that spindle speed output does not work right. Then could you add additional transformer positive and negative to the BOB outputs, same 12V vdc, but from another supply , so you kind of "help " it?????????

[cropwell]

Ok. Now that io have you here :-) , i have another quick question . If BOB has transformer that powers limit switches and at the same time spindle speed output, and you connect a couple of limit switches in series and find that spindle speed output does not work right. Then could you add additional transformer positive and negative to the BOB outputs, same 12V vdc, but from another supply , so you kind of "help " it?????????

In theory you could, but it is not good practice and I wouldn't recommend going anywhere near that solution.

How about a diagram of what you are doing with some component info ?

There is probably another issue here. I would guess that your 12v power supply might be under-rated for the job, but having said that I don't know what load you are pulling. You could try adding a reservoir capacitor across the power line and also some decoupling capacitors near the prox switches, just in case you have switching transients going back on the power line.

If you are talking about another 12v supply, why not use it for the sensors only and leave your working spindle speed controller alone ?

Cheers,

Rob

[Neale]

You say that you put two limit switches in series and it "does not work right". Does it work with just one limit switch connected? Does it work with no limit switches connected? I've been looking at a couple of examples recently where the BOB or motion controller has an analogue output for spindle speed, and it looks as if these often have a separate ground connection that should not be connected to the same ground that the limit switch inputs use on the BOB. I agree with Rob, though - it would be a lot easier to understand if you could provide a diagram and some details of the devices you are using. It's too easy to guess and make the wrong assumptions otherwise. If you are talking about spindle speed control here (not power to the spindle motor) it would be surprising if the problem was a lack of power because the limit switches and speed control inputs take quite low amounts of power. Interference is possible but shortage of power - probably not the problem.

[Boyan Silyavski]

Guys, i will not post more here, as it seems its for another thread. But i think you are right. There is something wrong maybe i have wired things especially the grounding and shielding. As a ground wire from here to there changes the spindle speed. I am not mixing VDC and AC and Earth. When i say ground i mean the shield that goes to common earth , where all PSU earth wires are connected together. I think the VFD and the servo drives mess things up. It could be as the VFD to spindle shield is wired both sides, one side to line ground, other side to spindle and machine body.

[MikeyC38]

Thanks for that, Rob - first time I've seen a representation of the switch internal circuit. I find those little extracts of both input and output circuits very useful in getting an understanding of how things go together, and especially when it comes to working out why something doesn't work! Too much detail for some, perhaps...

Now I'll have to draw out the combined circuit of four of those (NC versions) strung in series, so that I can use a single input for combined limit switches, just to reassure myself that it should work - even though I've wired it up on the bench and it does seem to.

Maybe some of us take a more theoretical approach where others just want to know where to stick the black wire

Just in case the OP is still with us and hasn't given up the will to live - this just confirms that your original wiring should be fine if you take out the resistor.

Hi Neale - I'm still here! Just about. But I must be having a brain fade because when I connect the black wire to pin 10, the blue wire to the pin 10 GND, then run a wire back to the -ve 24v supply it buzzes and does'nt work. I checked the GNDS on the ZP5A-INT board (it has a 5v supply from my Leadshine PS408/5 ), all the gnds are connected by doing a continuity check with the BOB unpowered from the -5v pin. I guess I just need to sleep on this and start again tomorrow. I must be missing something in what you guys have said and suffering from a case of "Goldfish brain"

[m_c]

I hope you mean +ve and not -ve.
.
Best to go back to basics, wire up just the power and gnd to the sensor, and use a multimeter to check that the output is switching. Provided that works, connect it to the BOB.

[MikeyC38]

These proximity switches come in so many flavours. The switch the OP is using switches to ground and an internal resistor makes no sense; the switch in the previous post switches to the supply rail and maybe an internal resistor is more useful.

If you use the NC version of the OP's switches, wired as suggested in series with the BOB input, you can connect a number of them to a single input. I have tested four in series, using 24V and a CSMIO, and that seems to work fine. Using the OP's NO switches, you would have to wire them in parallel but you lose the "fail safe" feature of NC switches.

Hi Neale - I gave up on this for a while but now my machine is working nicely I really do need to get my "fish brain" around this and get the homing set up with these proximity switches so that I can do auto tool setting height etc. So if I understand your post correctly I need to do this as shown in the attached picture



Choosing the appropriate value of R drops the voltage down enough for the input and away we go (hopefully!) .

I really appreciate all the posts from you guys on this.

Kind Regards
Mike