Prox Switch Help [Resolved]

[MSimeone]

You may have a defective sensor otherwise

Ill report back tomorrow morning once I get to the shop. I did have a thought - I am going to try using the 0V/COM directly from the connector on the Acorn board and see what happens. As I am thinking about it, the power supply for the Acorn jumpers the COM to earth. The power supply I am using to provide +24V and 0V to the prox sensors currently does not (at least I didn't do it externally, no idea if it does it internally). I can't help but wonder if that may be part of the issue? That power supply is a fairly high quality Weidmuller unit and it does provide proper power to release the Z axis motor brake via an Acorn output (i.e. the motor brake does function as expected via the Acorn PLC).

It is ok to use the Acorn power supply for the PROX sensors. If you are using a separate power supply for the sensors, then you must connect the 24v common from the power supply feeding the sensors to the Acorn common power supply. Otherwise it can not ground the Acorn input

Well darn, I'll bet that's it. I'll confirm tomorrow....

[MSimeone]

You may have a defective sensor otherwise

Ill report back tomorrow morning once I get to the shop. I did have a thought - I am going to try using the 0V/COM directly from the connector on the Acorn board and see what happens. As I am thinking about it, the power supply for the Acorn jumpers the COM to earth. The power supply I am using to provide +24V and 0V to the prox sensors currently does not (at least I didn't do it externally, no idea if it does it internally). I can't help but wonder if that may be part of the issue? That power supply is a fairly high quality Weidmuller unit and it does provide proper power to release the Z axis motor brake via an Acorn output (i.e. the motor brake does function as expected via the Acorn PLC).

It is ok to use the Acorn power supply for the PROX sensors. If you are using a separate power supply for the sensors, then you must connect the 24v common from the power supply feeding the sensors to the Acorn common power supply. Otherwise it can not ground the Acorn input

Well Marty, that was it! Thank you for your help and input - sometimes just talking something out is worth its weight in gold.
Question for you - since the COM on the Acorn power supply is jumpered to earth, should I also jumper the COM on the second PS to earth? Would this ensure that anything that needs COM/0V for an input or output coming from that PS is compatible? If so, would that have any possible negative effects on anything else? Thanks again!

[martyscncgarage]

Ill report back tomorrow morning once I get to the shop. I did have a thought - I am going to try using the 0V/COM directly from the connector on the Acorn board and see what happens. As I am thinking about it, the power supply for the Acorn jumpers the COM to earth. The power supply I am using to provide +24V and 0V to the prox sensors currently does not (at least I didn't do it externally, no idea if it does it internally). I can't help but wonder if that may be part of the issue? That power supply is a fairly high quality Weidmuller unit and it does provide proper power to release the Z axis motor brake via an Acorn output (i.e. the motor brake does function as expected via the Acorn PLC).

It is ok to use the Acorn power supply for the PROX sensors. If you are using a separate power supply for the sensors, then you must connect the 24v common from the power supply feeding the sensors to the Acorn common power supply. Otherwise it can not ground the Acorn input

Well Marty, that was it! Thank you for your help and input - sometimes just talking something out is worth its weight in gold.
Question for you - since the COM on the Acorn power supply is jumpered to earth, should I also jumper the COM on the second PS to earth? Would this ensure that anything that needs COM/0V for an input or output coming from that PS is compatible? If so, would that have any possible negative effects on anything else? Thanks again!

As I previously mentioned, the proximity sensors draw very little and can be run from the Acorn power supply.
If you are going to keep the auxiliary power supply it would be ok to jumper its com to its chassis ground. Do keep the COM between the two power supplies jumpered.

Marty

[MSimeone]

It is ok to use the Acorn power supply for the PROX sensors. If you are using a separate power supply for the sensors, then you must connect the 24v common from the power supply feeding the sensors to the Acorn common power supply. Otherwise it can not ground the Acorn input

Well Marty, that was it! Thank you for your help and input - sometimes just talking something out is worth its weight in gold.
Question for you - since the COM on the Acorn power supply is jumpered to earth, should I also jumper the COM on the second PS to earth? Would this ensure that anything that needs COM/0V for an input or output coming from that PS is compatible? If so, would that have any possible negative effects on anything else? Thanks again!

As I previously mentioned, the proximity sensors draw very little and can be run from the Acorn power supply.
If you are going to keep the auxiliary power supply it would be ok to jumper its com to its chassis ground. Do keep the COM between the two power supplies jumpered.

Marty

Alrighty Marty, all set. I took your advice and just used the Acorn +24V and COM. Thanks for the help! Keep those videos comin', haha!

[martyscncgarage]

Glad you are moving forward....

[cncbuiltbyme]

Thread was very helpful but I have a question about hooking up 3 prox. sensors in series? If you wire the NC sensors correctly, should the sensor's LED light go off for ONLY the sensor that senses an object near it while the other two remain on? Or should all three LED lights go off regardless of which sensor picks up an object?

[ShawnM]

That depends on where they are in the chain but it doesn’t matter since they are all wired to one input. When one trips it can take none, one or both the other switches with it if depending if they are upstream or downstream in the series. Again, it’s not an issue because once the machine backs off the tripped switch they all power up again. It may seem unconventional but it’s works. Make sense?

[Muzzer]

You simply can't be certain. Personally, speaking as a professional electronics engineer, I absolutely would not endorse putting 3 of these 3-wire NC sensors in "series" like this. The fact that some people will tell you that this technique works is fine for them but if you look at how they work and try to figure out the sequence of events during a switching event, it's very unclear exactly what will happen. I think you can be pretty certain that none of the reputable manufacturers would ever approve of this kind of connection scheme.

These aren't simply switches - they use an active circuit (oscillator) and a threshold circuit to detect the presence of a metallic object due to eddy current losses. When you switch one of the elements in the chain, you are disabling one of more of the others. Then you are sort of hoping they will come back and re-establish themselves quickly and dependably when that first switch decides to turn off again. It's not a behaviour that is characterised.

If you are making a professional machine, you will ensure you have enough spare inputs to be able to use these switches without using amateurish hacks like this. If you are not making a professional machine (which includes most of us here including myself) and you are still short of inputs, simply choose the normally open (NO) version which you can wire in parallel. Normal practice is to use NC switches but if this is your only controversial choice, you will be doing well. It's your call....

[ShawnM]

I agree that it's not the way a professional machine is wired and they would never do this but it does work for home switches on my DIY machines. It's worked for 3 years on one of my machines with zero issues. Supply them with 24 volts and nothing lower. I'm using the very same prox switches from eBay and/or Amazon, the Roko branded ones made in China, that Centroid has on their website. Is it the "proper" way to wire them? Maybe not but it does work so wire it this way at your own risk. Your mileage may vary.

I would choose to wire 3 NC switches in series before I ever used a NO switch on my machine.

If you have the extra inputs or want to spend the extra money for an ether 1616 then of course wire each sensor to it's own input if you need the extra piece of mind.

[cncbuiltbyme]

Thanks guys for your replies. I'm still trying to wrap my head around this. The videos I've seen so far for configuring proximity sensors for Acorn say to use "NC switches in series". I actually have 3 NC sensors as well as 3 NO sensors so I technically could use either set. Just want to do it correctly and "professionally". Currently, I am using the NC sensors. For testing purposes, all 3 brown wires from the 3 sensors are connected to 9V+. The X-sensor black wire is connected to 9V-. The X-sensor blue wire is connected to the Y sensor black wire. The Y-sensor blue wire is connected to the Z-sensor black wire. The Z-sensor blue wire is not connected to anything yet. With this configuration, each sensor's LED light goes off when metal is detected and only that sensor LED light goes off. The other two sensor LED lights remain lit (unless either one of them detects an object, then they too switch off). In other words, each sensor works independently of the other sensors. Is this the correct way the sensors should work?

BTW, looking into setting up each sensor into its own input but still would like to know the answer to above question.