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two pots for one VFD

J

JoshNZ

Aluminum
Joined
Jan 16, 2018
I have a VFD controlling a 3 phase motor that I wish to control from two seperate panels depending on which side of the lathe I'm using.

On the main side is start/stop momentary push buttons, a 2-pos fwd/rev switch, and a pot. On the other side is start/stop and a pot. Ideally I'd like to set the VFD frequency source to the pot belonging to the side that started it.

I can't think of any elegant way to do this without giving up the start/stop buttons for a single latching button each side, or relays, or a PLC. Is there an obvious solution?

The drive is a delta VFD015B21A.

Thanks in advance as always
 
JoshNZ said:
I have a VFD controlling a 3 phase motor that I wish to control from two seperate panels depending on which side of the lathe I'm using.

On the main side is start/stop momentary push buttons, a 2-pos fwd/rev switch, and a pot. On the other side is start/stop and a pot. Ideally I'd like to set the VFD frequency source to the pot belonging to the side that started it.

I can't think of any elegant way to do this without giving up the start/stop buttons for a single latching button each side, or relays, or a PLC. Is there an obvious solution?

The drive is a delta VFD015B21A.

Thanks in advance as always
Click to expand...

Common enough, lots of "stuff" was a "Local-Remote" switch. The simplest of switch contact forms - SPST, even - can control a relay with insanely complex switch forms. See "T-bar relay".

Wise to do the switching whilst the VFD is OFF, of course.

A smooth hand-over is do-able, but a tad more thought and different components are wanted.

Not worth it unless you are doing Morris Dancing or kinky sex with the lathe as intimate partner.

:D
 
JoshNZ said:
I have a VFD controlling a 3 phase motor that I wish to control from two seperate panels depending on which side of the lathe I'm using.

On the main side is start/stop momentary push buttons, a 2-pos fwd/rev switch, and a pot. On the other side is start/stop and a pot. Ideally I'd like to set the VFD frequency source to the pot belonging to the side that started it.

I can't think of any elegant way to do this without giving up the start/stop buttons for a single latching button each side, or relays, or a PLC. Is there an obvious solution?

The drive is a delta VFD015B21A.

Thanks in advance as always
Click to expand...

Common enough, lots of "stuff" was a "Local-Remote" switch. The simplest of switch contact forms - SPST, even, SPDT better - can control a relay with insanely complex switch forms. See "T-bar relay". Potentiomete only owns three wires, not all even have to be switched- just the "slider" tap, so that part is not hard,

SPDT switch, "direct" can do, DPDT better. (At least) one end of the pot can be left common.

Wise to do the switching whilst the VFD is OFF, of course. You don't want sudden jump's in RPM if you've left one at t'other end of the range than its sibling.

A smooth hand-over is do-able, even IF they are at widely divergent setting. A tad more thought and different components are wanted, but nothing as complicated as a PLA.

Just use a 3 position transfer switch with a center position tapping a fixed resistor or a trimpot set for mid-range. Pause briefly, let the RPM catch up, finish the transfer.

You need "all store bought" goods? Just add the remote network card to your VFD and connect as many remote control workstations, any continent on-planet, ships at sea, or spacecraft in Earth's orbit as you feel like enabling.

Nearly all VFD have some form of network bus so a whole tribe of them can march their motors in lockstep under a mile long conveyor belt full of Iron ore or wotever. Control booth may not even be in the same county, and may not be human.

:D
 
I'm pretty limited on space on my panel if I'm to use the original is all. If I have to use relays or control switches I think I'd already know how to do it but I figured there must be a way to do it using the VFDs functionality I just haven't put the pieces together yet.

If I could wire it so the start switch held a multifunction terminal sinked.. sunk..? I could set the frequency source based off this. But then I'd need a latching start button or a relay.

Is there any reason I shouldn't use two incremental potentiometers? Encoders.. Whatever you call them I'm not sure of the name but a knob that pulses on one terminal as you turn it clockwise and on another as you turn it anticlockwise. I could wire them both in parallel and connect to MF terminals, there are parameters for increasing/decreasing master frequency by X units attached to those. Then they would both always work without upsetting each others position. Any reason that wouldn't work? :confused:
 
JoshNZ said:
I'm pretty limited on space on my panel if I'm to use the original is all. If I have to use relays or control switches I think I'd already know how to do it but I figured there must be a way to do it using the VFDs functionality I just haven't put the pieces together yet.

If I could wire it so the start switch held a multifunction terminal sinked.. sunk..? I could set the frequency source based off this. But then I'd need a latching start button or a relay.

Is there any reason I shouldn't use two incremental potentiometers? Encoders.. Whatever you call them I'm not sure of the name but a knob that pulses on one terminal as you turn it clockwise and on another as you turn it anticlockwise. I could wire them both in parallel and connect to MF terminals, there are parameters for increasing/decreasing master frequency by X units attached to those. Then they would both always work without upsetting each others position. Any reason that wouldn't work? :confused:
Click to expand...

I haven't looked at your delta, but... a Eurotherm/parker-SSD can use either of a sourced voltage OR a pot sinking off its own supply rail.

So yes, AFAIK, you could do speed setting with stable, regulated, and referenced voltage sources.

I'm lazy. I'd want to run a shaft under the carriage, one pot, two knobs - or across at HS or TS.. or put the controls on a pendant or wireless device.

Last and ONLY lathe I ever used that needed this was a pre-1900 Niles Tool Works 6-foot-swing "Horizontal BORING lathe". It had catwalks to an operator stand-on platform with control wheels, one each side of the HS. Even that was only because the spindle had several feet of "advancing quill" travel - like the horizontal boring mills that were already evolving to replace it.

I presume you have a similar challenge to even NEED controls at more than one position.

Massive old dinosaur of a manual lathe, is it?

One of our "newer" Niles - War One era - had been kitted-out later with a tubular swing-arm and pendant control. That was mainly so one had "jog" to deal with getting the 4-Jaw to where yah didn't have to climb up as far to adjust the jaws. Bit less than six-foot swing, that one.

One RAN it from the usual stance at the carriage, controls left to old skewl longitudinal rods with duplicate-function hand-levers, one each, left and right side of the apron.
 
An encoder does not "pulse(s) on one terminal as you turn it clockwise and on another as you turn it anticlockwise". It sends out 2 streams of pulses. The pulse frequency of each stream is proportional to the speed at which you turn the shaft, and the phase relationship between the 2 streams is different depending on which direction the shaft is being turned.

They may exist, but I've not seen a VFD that could take input from an encoder to set the output frequency.

The common analog method of controlling VFD speed uses a 0-10VDC signal, which is varied to set the speed. A potentiometer is often used to do this, but any circuit that can safely supply the 0-10V signal will work. Usually, the input on the VFD is NOT isolated from the mains, so you would need some method of isolating your control circuit from the mains.

To control it from 2 different positions, you might consider momentary switches for increasing and decreasing the speed. You could use a device like this one:

DC-2 DigiSpeed XL [DC-2] - US$56. : Homann Designs!, Your preferred CNC Supplier

to accept the inputs from the UP/DOWN momentary switches, and send the 0-10V signal to the VFD. Theoretically, you could hook up as many control stations as you wanted with a setup like that.
 
I'd be too scared to be in the same room as a lathe that big aha... It's just a wood lathe actually but I've machined a spindle with a RH thread on the outboard end for turning larger pieces, right handed, standing at the back. So the backside panel is a matter of convenience. Nothing is essential but I figure I might as well do it right (or as right as possible) while it's apart with wires hanging out everywhere.

The rod isn't a bad idea actually :). If I can't come up with something simple I'll get drilling.

So the encoder idea is off the table. How does a circuit logically determine which way an encoder is turning if the pulses are on the same terminal? What are those dials called on those car stereos that turn infinitely, but volume goes up CW and down CCW? The momentary buttons would work on their own but I'd sooner fit a remote-switch than 2 more buttons. And I'd prefer a dial.

The VFD has its own 10V power supply for the pot. It has an analogue input and an auxiliary input and you can select which one the drive 'listens to' by holding an input terminal to common or leaving it open. The only way I can think of achieving exactly what I'm after is using a latching relay driven from the momentary start button to hold the input terminal where I want it. Or I can use a latching on/off button, is that very common or unsafe on a lathe?

The rod is starting to sound pretty simple :D
 
JoshNZ said:
I'd be too scared to be in the same room as a lathe that big aha... It's just a wood lathe actually but I've machined a spindle with a RH thread on the outboard end for turning larger pieces, right handed, standing at the back. So the backside panel is a matter of convenience. Nothing is essential but I figure I might as well do it right (or as right as possible) while it's apart with wires hanging out everywhere.

The rod isn't a bad idea actually :). If I can't come up with something simple I'll get drilling.

So the encoder idea is off the table. How does a circuit logically determine which way an encoder is turning if the pulses are on the same terminal? What are those dials called on those car stereos that turn infinitely, but volume goes up CW and down CCW? The momentary buttons would work on their own but I'd sooner fit a remote-switch than 2 more buttons. And I'd prefer a dial.

The VFD has its own 10V power supply for the pot. It has an analogue input and an auxiliary input and you can select which one the drive 'listens to' by holding an input terminal to common or leaving it open. The only way I can think of achieving exactly what I'm after is using a latching relay driven from the momentary start button to hold the input terminal where I want it. Or I can use a latching on/off button, is that very common or unsafe on a lathe?

The rod is starting to sound pretty simple :D
Click to expand...

EVERYTHING is potentially "unsafe on a lathe". So is flying airplanes, but folks learn to do it and live.

Rear stance, wood lathe, was common, our school shop. Our glued-up laminates turned into bitchin' good looking salad bowls for our Mum's. Before you could afford to "just BUY" such things.

I was averse to wood MOVING every which way when humidididty changes, so took up metal spinning lathe that year instead.

For your use, I might fit a plug-in cordset with a foot switch on the floor, Singer sewing-machine inspired. Need some training-up, much like getting used to picking up loose eggs with a forklift.

OTOH, payback could give you hands-free RPM change as you traverse the bowl radius.

My late Uncle developed a foot-control and mating torch for lamp-glass workers to allow flame change whilst both hands were knitting glass. Mind - those were used from a seated position, as with driving a vehicle.

2CW
 
looking at page 2-14, it looks very simple to do.

A switch to select which pot you use, and off you go. Only the "AVI" needs to be switched, the +10V, and the "ACM" are the same for both pots.

I would suggest a resistor of a reasonably high value, perhaps 47k (47,000) ohms, from "AVI" to "ACM". That will tend to make the "default" be a zero speed input, so if the switch does not make contact for some reason, the input will go to a zero speed value. (I am assuming the designers had enough sense that the input would go there anyway, but....).
 
JST said:
I would suggest a resistor of a reasonably high value, perhaps 47k (47,000) ohms, from "AVI" to "ACM". That will tend to make the "default" be a zero speed input, so if the switch does not make contact for some reason, the input will go to a zero speed value. (I am assuming the designers had enough sense that the input would go there anyway, but....).
Click to expand...

"Usually", yes. Mighty easy to CONFIRM, though, ain't it?

:)

One could also utilize a SPDT switch with "transfer" or make-before-beak contact form rather than break-before-make. Lots of those were used in Telco and Audio to reduce "pop" taking out sensitive stuff.. eardrums, f'rinstance.

2CW
 
I realise that's essentially what needs to happen I just wanted to know if there's a way to do it without manually switching it over, as my panel won't fit another switch.

I could use a relay to do it and control it with the start/stop switch and then hide it in the VFD enclosure somewhere else. I could wire it through a second pole on the fwd/rev switch as well. It'll mostly be used in reverse from the back and forward from the front, mostly...

Another thing that's driving me nuts about this manual is the multifunction relay output terminal. Specs are below. Is it 240VAC or 24VDC :angry: There isn't any information about programming or setting it.

Resistive Load:
5A(N.O.)/3A(N.C.) 240VAC
5A(N.O.)/3A(N.C.) 24VDC
Inductive Load:
1.5A(N.O.)/0.5A(N.C.) 240VAC
1.5A(N.O.)/0.5A(N.C.) 24VDC
Refer to Pr.03-00 for programming
 
Naturlich.

Every one I know about defaults low, but there is the chance of an outlier. Can't think why that would be a good idea, but no harm (and much good) in checking.

I am not too sure what I would suggest if the thing defaulted high.....any effective pull-down to zero would load the pot pretty heavily,,,, You would want to make it default low, and if a make before break can be found, that would certainly be a help, as it might relieve the need for a loading resistor somewhat.

If any guy I supervised came up with a default high speed for a general purpose VFD, I would have a few words to whisper in his ear.....
 
JST said:
If any guy I supervised came up with a default high speed for a general purpose VFD, I would have a few words to whisper in his ear.....
Click to expand...

LOL! "You're fired!" I'd guess. I had the need of simply firing a Director of Engineering shortly after taking-on a new role. Some just aren't salvageable.

He'd put together a pan-Caribbean credit card clearing service he was about to roll-out. Our unit prez asked him to show us how he was going to handle "baulked" transactions.

Think cruise ship just unloading a thousand souls onto an island port's shops in a short span of time, and some of them whose cards were going to decline, if only for unexpected venue. Looong line of other customers back of them, fuming over any delay, the merchant frantic over live-or-die biz.

He'd no klew what such a transaction even WAS! Then had the arrogance to claim it didn't MATTER!

Didn't help his longevity that the Unit Prez had come back to pick-up on 26+ years with C&W after a ten-year detour in charge of building out a global clearing network for a little country-bumpkin called "American Express".

HE.. certainly DID know it "mattered", and greatly so!

Staff may get "second chances". Directors, not so much.
:)
 
Yes it is I could lean over the work or walk around. Would no doubt have my shirt ripped off my back one day lol. As I said I'm just trying to figure out the most right way to do it first time round.

A latching on-off pushbutton switch, with 2 poles, one for starting and one for directing the wiper terminal to the 0-10V signal terminal is probably the easiest solution...?
 
A few possible options, Josh... and by the way, welcome to PM!

First... your current panel doesn't have enough room for another switch, but let's say you run your VFD control wiring to the BACK panel, and put the selector switch THERE... then take your wiring from the switch to the front panel...

Another possibility- make just one control panel with speed and direction, and make it on an arm that flips from one station to the other...

I would (if I were doin' what you're doin'... ) put a foot-operated kill switch of some type... so that if things got out of hand, it'd shut the spindle down pronto.

I would NOT want to go with an encoder for speed control in this circumstance just for one reason- you have a 'T' in your wiring that becomes somewhat of an antenna, and the VFD is a hideous broadcaster of RF hash noise... it may 'get into' the encoder signal enough to give it a terrible case of Digital Tourettes Syndrome.

What if...

What if your control station for bowl turning was symmetrical (meaning, you worked from either side, in the same way) and your need to vary the speed with diameter was such that a treadle control was a viable option? If that's the case, then a shaft at floor level, with treadle-board on it, linked to your potentiometer, with spring return on BOTH, would resolve the electrical issue, and the spring return acts as a safety net... AND you can keep both hands on your turning tool while you move from center to edge...
 
I definitely don't need to vary speed during cut haha, wood feed speed is not so critical as with metal turning, we do get to finish with sandpaper.

Strike encoder off the table, good point.

The foot kill switch would involve a bar through the headstock, or two switches, as the stances are staggered. I'll probably put a big mushroom on it somewhere anyway.

I toyed with the idea of a pendant and swinging arm too but it just won't suit the lathe. It's an old union graduate, ugly as sin, all curves and no flats, it just wouldn't look right and there's nowhere it wouldn't be in the way.

I could have the remote throw switch on the back panel that's not a bad idea, since there is nothing there now its going to be an enclosure mounted to the lathe anyway so can be whatever size. I'd only need a 3pole switch for start/direction/pot, stops can go in series so they both always work which isn't a bad thing. I'll prob do this. Thanks!

The other option I haven't completely eliminated is starts and stops in series, both always work, but each start button throws a latching relay to its own side, which connects the pot from that panel to the VFD. Any reason this is a silly idea...?

Thanks for the ideas
 
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