Input for linear slide actuator

[ADWSystems]

With Optos:
View attachment 90643
View attachment 90644
View attachment 90645
Feed the "Analog Pin" value to an Analog I/O monitor that value.

Sorry cowboybob, no analog available. Adding a comparator on top of the rest of that circuit will get the proposal turned down...too much hardware. this is not a one-off there are many of these and their are adding more.

 

[ADWSystems]

Why do I think I (we) went a long way around for a very simple answer?

I think all I need to do is swap the wires on the switches (common and NO). Better yet, IIRC they are quick connects not even soldered.

Here is the circuit with the slide having traveled to the left.

Yes when the slide first starts to move, the input will come on. So instead of changing 1 line of code I will have to also add 1 (wait for Input=0 then wait input =1).

 

[ccurtis]

By Joe, I think you've got it.

 

[KeepItSimpleStupid]

Quick connects in a vehicle of some sort? My advice: Start over
when is the last time you saw a quick connect in a vehicle? Now bullet connectors, Yes.
Use automotive connectors.

 

[cowboybob]

At the point indicated, 12VDC or 0VDC is present depending on the conditions of RY2, S5 and S6. Simple 0 and 1 digital conditions, only swapped when the slider engages either the OPEN or CLOSED limit switch, demonstrated with an LED below:

or (OPEN):

If you trace the lines, (and this is confirmed in the SIM), either logic condition is held until the slider engages the limit switch towards which it is headed (having disengaged from the the limit switch that it is leaving).

I can put up graphics of EACH STEP for the switch conditions is you like.

 

[ADWSystems]

I agree the LED point will be 12V or 0V. The circuit needs to differentiate between limit switch and travelling. Unfortunately I don't see that in this circuit, yet.

At Point D:
Travelling FWD =12V
FWD Travel Complete =0V
Travelling REV =0V
REV Travel Complete =12V

The voltage out for travelling and travel complete are different depending on if it is travelling FWD or REV. Which is what I think cowboybob is saying. but that still provides two different voltages for FWD Complete and REV Complete.

P.S. Sorry about the upside down relays, I wanted to show them in position so I (and everyone else) can follow.

 

[cowboybob]

I agree the LED point will be 12V or 0V. The circuit needs to differentiate between limit switch and travelling. Unfortunately I don't see that in this circuit, yet. ....

This would be impossible without some manner of additional testing/proofing that the slider, itself, is actually moving.

Are you saying that a positive indication (that either the FWD or REV limit switch had transitioned), within a specified period of time, is insufficient as proof of a successful slider event?

As it stands, the circuit above only transitions when one or the other limit switches is hit. Should that not happen, (again, within a fixed time frame) an error in slider movement (or some electrical/motor error) would be a reasonable assumption of a fault that then could be used to initiate some manner of process shutdown.

<EDIT> I am assuming the limit switches are spring loaded types, i.e., they have a normal NO-NC arrangement that, when pressed, transitions to NC-NO, to then transition back to NO-NC when released. Is that correct?

 

[ADWSystems]

This would be impossible without some manner of additional testing/proofing that the slider, itself, is actually moving.

Not impossible. Just a different train of thought. Either limit switch contacted =1, neither limit switch=0. From there it is a matter of making a circuit do just that. I'm hoping to develop a solution that runs one additional wire (instead of two) back to the controller and have no where on the slide to mount circuitry (as there is none there now). Those design criteria make the problem and solution more difficult.

Are you saying that a positive indication (that either the FWD or REV limit switch had transitioned), within a specified period of time, is insufficient as proof of a successful slider event?

I was thinking positive indication as the same indicator from either end.

It's funny how you can write the same thing two different ways...

If you trace the lines, either logic condition is held until the slider engages the limit switch towards which it is headed (having disengaged from the the limit switch that it is leaving).

As it stands, the circuit above only transitions when one or the other limit switches is hit.

...and come up with two different ideas. I had no idea how to handle the scenario as I read it in the first post, but in the second I know exactly how. Currently the logic is Delay(x). I was hoping to just change it to Wait(Input==1). My solution would be Wait(Input==0) then Wait(Input==1); I think. This design would be If (Travel==FWD) then Wait(Input==) else If (Travel==REV) then Wait(Input==0). I can work with that. It's funny how I did not get that from the wording in the first post, but is all I can see from the second. We are just missing the 7:5 ratio resistor divider at port D to cut down the input voltage.

<EDIT> I am assuming the limit switches are spring loaded types, i.e., they have a normal NO-NC arrangement that, when pressed, transitions to NC-NO, to then transition back to NO-NC when released. Is that correct?

That is correct. The limit switches are just those spring loaded lever type.

 

[Reloadron]

In the below circuit LEDs D1 & D2 illuminate when their respective limits are met. Both D1 and D2 could easily be replaced by opto couplers. The problem here is working from an existing circuit and keeping the parts count down. Being a small motor drawing <600mA reversing and control is relatively easy. Modifying the existing circuit isn't quite as easy as starting from scratch.

Anyway, opto couplers could be used to provide the logic outputs.

Ron

 

[cowboybob]

ADWSystems, we're simply talking around the same solution:

1. two, distinct voltage values (the logic) on a single (one wire) connection (Gnd {0} and Vcc {1}) that only occur at distinct slider positions
2. an assumed slider movement, confirmed by 1. above, within the "wait" code (an assumed code timeout on the "wait" to capture a slider error).

Whatever the logic choice (voltage divider or opto-isolator), you should add a diode to the circuit (as below) to ameliorate any back EMF from the motor when it is turned off:

Unless, of course, I've missed something thus far...

 

[Reloadron]

Cowboybob, looking at D1 in your drawing, what happens when the motor polarity is reversed? As drawn the cathode is on Motor + and anode is Ground but when the motor reverses what happens? Most reversing brush type motors we just place a cap or three across the terminals and each terminal to the motor case, generally 0.1 uF.

Ron

 

[ADWSystems]

Quick connects in a vehicle of some sort? My advice: Start over
when is the last time you saw a quick connect in a vehicle? Now bullet connectors, Yes.
Use automotive connectors.

Vehicle? Automotive? This is on production equipment, a motor and leadscrew driven linear slide.

As for quick connects in cars, I see plenty of them. Bullet, spade, lug, and butt connectors. I only see splices used by amateurs and DPOs.

 

[ADWSystems]

ADWSystems, we're simply talking around the same solution:

1. two, distinct voltage values (the logic) on a single (one wire) connection (Gnd {0} and Vcc {1}) that only occur at distinct slider positions
2. an assumed slider movement, confirmed by 1. above, within the "wait" code (an assumed code timeout on the "wait" to capture a slider error).

I can follow your logic and will be drafting it today, but how it works is not the same as the expectation. The expectation was similar to Ron's drawing, only a result at the switch (1) and nothing (0) in between (while travelling). Your logic provides the same signal during travelling as one of the limit switches. Since the motor controller and the sensors are tied to the same processor it is possible to integrate your logic; because I know the commanded direction of travel I know which signal (0 or 1) to look for.

 

[cowboybob]

Cowboybob, looking at D1 in your drawing, what happens when the motor polarity is reversed? As drawn the cathode is on Motor + and anode is Ground but when the motor reverses what happens?

Ron

Nothing , since the cathode would also be grounded. Any back EMF generated from the motor running in reverse would be applied to the 12VDC Vcc line feeding the - motor connection.

 

[cowboybob]

ADWSystems,

Keep in mind the the logic of either slider position (full REV or full FWD) is maintained until its opposite position is attained, at which point it swaps and is held until the next transition.

 

[ADWSystems]

ADWSystems,

Keep in mind the the logic of either slider position (full REV or full FWD) is maintained until its opposite position is attained, at which point it swaps. and is held until the next transition.

I understand that, it took me and you an extra post to switch my gears. Do you see that is not what was expected?

The expectation was 1 at the limit and 0 during travel. (life would be great if everything was this simple)
-The preferred option would be: 0 at the starting limit, 0 during travel, and 1 upon reaching the ending limit. Ron has it in post #29, but I will need to see if they will add the hardware (extra wire, pr of resistor/optos, connectors, etc.).
-My circuit in post #22 has, 1 at the starting limit, 0 during travel, and 1 at the end limit. This would require hanging resistors from the switches to field cables, or running both other switch pols back to the cabinet (similar to Ron #29).
-Your solution as (a) if travelling forward then 0 during the travel and 1 at the FWD Limit and (b) if travelling reverse then 1 during travel and 0 at the REV limit. So the signal depends on the direction of travel. No exactly analogous to the expected logic. Doable, but I will need to get them on board and to change their thinking the same way I had to. This has one wire and one resistor/opto pair.

 

[Reloadron]

Here, this should be a solution:

The limit switches were moved upstream from the reversing relay logic. When either limit is met you get a logic 1 of 12 volts, less if you use a divider. This is as simple as I can see it working. I did not label Fwd / Rev but as drawn the logic is pretty simple as to what is open and closed. Also not shown is a diode across the FWD / REV Relay coil.

Will this fly?

Ron

 

[cowboybob]

ADWSystems,

I should point out (and you may have noticed) that Vcc (logic{1}) is held except during a very short (a few mS) time when the cross-over relay contacts mechanically transition from REV to FWD (a momentary negative "blip"). This might require a Delay command prior to the Wait call to allow for this transition.

 

[ADWSystems]

ADWSystems,

I should point out (and you may have noticed) that Vcc (logic{1}) is held except during a very short (a few mS) time when the cross-over relay contacts mechanically transition from REV to FWD (a momentary negative "blip"). This might require a Delay command prior to the Wait call to allow for this transition.

I knew that would happen but I wasn't worried about it. Actually, way way way back, there is a power (GO) relay between the power supply and the direction relay. No one has drawn or worried about, but it is there and doesn't effect the back end on which we have been working. Once the direction relays are set, then power is applied for x amount of time (currently). Instead of x time, the program will wait for all switches to be in position.

 

[ADWSystems]

Here, this should be a solution:

View attachment 90672

The limit switches were moved upstream from the reversing relay logic. When either limit is met you get a logic 1 of 12 volts, less if you use a divider. This is as simple as I can see it working. I did not label Fwd / Rev but as drawn the logic is pretty simple as to what is open and closed. Also not shown is a diode across the FWD / REV Relay coil.

Will this fly?

Ron

Ron, what's the capacitor for?

Keep in mind the motor is mounted with the switches, which is away from the direction relay and power source. Currently it runs from a 2C cable, I'm trying to convince them to rewire with 3C. I think the new layout would require 6 or 7 conductors (2-motor, 1- power to sw common, 2 for limit sw NC, 1 or 2 for the limit sw NO)