two pots for one VFD - Page 2
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  1. #21
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    Quote Originally Posted by JoshNZ View Post
    Any reason this is a silly idea...?
    I'd be tempted to shitcan the VFD for a single-speed 1-Phase motor, some Vee-belt cone pulleys, and one "oil burner" toggle switch so I didn't have all the headaches to deal with at all.

    All you seem to REALLY need is some form of "E Stop" near each work position, and "maybe" a bit of re-purposed railing to define a safety "cell".

    The VFD is making a problem out of a solution!

    Not the first time, either. I have one left to throw away meself. When I find it. Never been hooked up.

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    Well I just pulled a single phase motor out of it so that would really be taking backwards steps lol.

    It had stop and start, and 4 sheaves at each end, you had to lift the lid and then get down on your knees and lift the motor for the other end and bla bla. I could do start, stop, and a pot, and it would already be a thousand times better than it was. The 3 phase is silent, when you hit start on 10hz the loudest noise coming from the lathe is the belt squeaking away. I was worried it wouldn't have any torque going slow even in vector mode but if you grab that spindle too enthusiastically it'll peel your palms right off lol. Which makes it great for getting big ugly unbalanced chunks started.

    On the outboard was a LH thread. Good for nothing. Neither threads were good for anything anyway I couldn't find any chucks or plates to fit so I changed them both to RH, of novas biggest thread. Made the outside useless unless it ran backwards so that was the nail in the coffin for going VFD+3ph. Big unbalanced chunks can be bigger with the outboard clearance so it has been a great thing.

    And I love it. If I have to go on off pot on one side I'll still love it. But as I said while it's in bits I'll do it right.

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  4. #23
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    Your panel won't fit another switch? Not even a miniature, on the side?

    You are making up limitations.

    Bugger off!

  5. #24
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    OK, stupidly simple system.... works well, but you need to remember to turn the speed pot to zero when done. That is not very restrictive, it is good practice, so it should work. There will be a slight limit on the top speed, which may not be an issue.

    What you do, is to connect both pots to the 10V and the "ACM" (analog common) as shown in the manual.

    For the "sliders" of the pots, you connect them to the analog input, BUT each one goes through a diode.... a 1N914 or 1N4148 would be acceptable. The end with the "bar" marked goes to the analog input. You still do the resistor to ACM that I mentioned, and I think I would also add a 0.1 microfarad capacitor in parallel with the resistor, to get rid of "noise".

    So,,,,, now whichever pot is turned to the highest setting is in control. NO SWITCHES NEEDED. The unused pot you simply turn down to zero, which automatically puts the other one in control.

    The one disadvantage is that the diode "drops" a little voltage, which means you will miss getting to the full top speed setting by about 7 percent or so. I do not think that is a huge compromise, but YMMV.

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    Quote Originally Posted by JST View Post

    The one disadvantage is that the diode "drops" a little voltage, which means you will miss getting to the full top speed setting by about 7 percent or so. I do not think that is a huge compromise, but YMMV.
    can get rid of that in the vfd programming.

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    Quote Originally Posted by johansen View Post
    can get rid of that in the vfd programming.
    Yes, on many you can. I did not look for that function in the manual. And it is a complication that may not be necessary. But it is likely possible.

  8. #27
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    Quote Originally Posted by JST View Post
    OK, stupidly simple system.... works well, but you need to remember to turn the speed pot to zero when done. That is not very restrictive, it is good practice, so it should work. There will be a slight limit on the top speed, which may not be an issue.

    What you do, is to connect both pots to the 10V and the "ACM" (analog common) as shown in the manual.

    For the "sliders" of the pots, you connect them to the analog input, BUT each one goes through a diode.... a 1N914 or 1N4148 would be acceptable. The end with the "bar" marked goes to the analog input. You still do the resistor to ACM that I mentioned, and I think I would also add a 0.1 microfarad capacitor in parallel with the resistor, to get rid of "noise".

    So,,,,, now whichever pot is turned to the highest setting is in control. NO SWITCHES NEEDED. The unused pot you simply turn down to zero, which automatically puts the other one in control.

    The one disadvantage is that the diode "drops" a little voltage, which means you will miss getting to the full top speed setting by about 7 percent or so. I do not think that is a huge compromise, but YMMV.
    Clever idea! It's definitely possible to get back your full range with analogue bias and gain parameters and I considered something similar, the VFD has provisions for it in its parameters without the circuitry. But I thought one day I might mount something ugly to the back side and hit go with the pot turned all the way down, forgetting the front pot is left up. Wouldn't be a major probably but reason enough to flag that idea too.

    Quote Originally Posted by CalG View Post
    Your panel won't fit another switch? Not even a miniature, on the side?

    You are making up limitations.

    Bugger off!
    The panel size is 65mm wide by 88mm tall, less the wall overlap, and the cavity in the cast is only 50mm or so deep. I've already got four 30mm controls on it, I doubt I could fit another switch on the front let alone the triple pole ass end of it behind the panel. It was only made for start and stop. I'm going to put the switch on the back as was suggested anyway. Won't need those controls until I get around the back so it might as well go there

    Thanks again for all the ideas and help

  9. #28
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    Quote Originally Posted by JoshNZ View Post
    ........ But I thought one day I might mount something ugly to the back side and hit go with the pot turned all the way down, forgetting the front pot is left up. Wouldn't be a major probably but reason enough to flag that idea too.
    .......
    That is no more likely than just forgetting to switch to the backside pot.

    Less, maybe, as you had to turn down the speed when stopping on prior part. Unless you just hit the power switch, which is bad practice with a VFD.

    At some point, there are things that you just need to do right.

    And if it starts up when you do not expect it, hit the E-stop. You need an E-stop at each operator position.

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    Yes I still haven't figured out the e stop. Will probably go on top of the headstock within reach of both otherwise separate foot switches.

    If you tried to start it before switching controls it wouldn't start because the switches won't be connected to the vfd. So I meant having a multiple pole switch that changed start and the pot, and fwd/rev which I'm thinking I'll have on the back now too.

  11. #30
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    I would suggest the simplest option is to use a single dual (or three) pole ice cube type relay. Add a NC closed switch block to each stop button and serially connect a 12 or 24V power source which then goes to the common terminal on the relay (side 1) which is also connected to a NO switch block on the monetary RUN switch of the second pod. Output of Side 1 of the relay NO and the NO Run switch both go to the + side/relay power. The second side of the relay common goes to AVI speed terminal, NC goes to wiper of speed pot 1, NO goes to wiper of speed pot 2. When you press run command in the second control pod, it latches the relay and selects speed pot 2 until either stop button is pressed. Default connection is control pod 1. So one relay and a power source, simple to implement. There may be some non-linearity in the speed pot because in either configuration it will see a separate resistance of the other pot across the ACM and +10 terminal, one could use a 3 pole relay and also switch the +10 in addition to the AVI. The relay would be in the VFD enclosure.

    I have seen lathe setups with the E-Stop and speed pot in the center of the lathe either mounted on an arm on the top of the splash shield or it could be in the center at the drip pan level. I have also rigged a safety stop system to be on a perimeter wire safety stop or bar (all stops are serially connected). My safety stops are wired to a power relay, so when tripped they brake the VFD quickly and power down the run commands. So takes a reset to reactivate the VFD run commands.

    I have done a few VFD lathe systems where I used a single centrally located control pod at the drip pan level, used monetary buttons for Run Forward, Stop, Run Reverse. This allows quick reversal without needing a sustained direction switch. These systems use latching relays to issue the run commands via 2 wire control vs. 3 wire.

  12. #31
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    Quote Originally Posted by JoshNZ View Post
    ...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 encoder has 2 outputs, and they are NOT both on the same terminal. The 2 outputs are out of phase with each other by 90 degrees(1/4 wavelength). So if you turn the encoder in one direction, you see a pulse from output A, wait 90 degrees, see a pulse from output B, and then wait 270 degrees for the next pulse (from A again) in one direction. When the encoder is turned in the other direction, the "90 degree" separated pulses are in the reverse order; first B then A.

    Like this:

    CW: A-90-B-270-A-90-B-270.....
    CCW: A-270-B-90-A-270-B-90-A.....

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    Quote Originally Posted by JoshNZ View Post
    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
    You use a small control box with a speed pot that has a magnetic back. Move the box.

    I bought one of those Delta VFD's years ago to inspect it. Then I returned it. Just like a Teco, landfill electronics.

  14. #33
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    Quote Originally Posted by JoshNZ View Post
    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.
    The way it is done for outboard turning is a left-hand thread on the left-hand side of the spindle. All turning is done from the front. I have a 6 inch face plate that has both a right and left-hand thread and screws on either side of the spindle.


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