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

[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.