VFD remote (pendant) design

[Gene PavlovskyParticipant @genepavlovsky]

[Gene PavlovskyParticipant @genepavlovsky]

Hello everyone.

I've used the search function but haven't found any results.

I'm converting my little Hobbymat MD65 lathe to VFD and am looking into how to control the VFD. I'm sure the keypad on the VFD is meant only for setup/testing, as the buttons are very small and don't have a good "feel".

The simplest option would be to just use the two 2-position rotary switches on the lathe, and just add a potentiometer to the panel for speed control. Perhaps an emergency stop button would also fit on the panel. Do I want extra features, such as e.g. Jog, Fast-Stop (dynamic braking)? Would these be useful on a lathe? (maybe for screw-cutting? although a carriage auto stop rigged to the Fast-Stop input of the VFD would be more handy)

The second option is an external remote / pendant / control box, which can be sized to include all the controls I could want, perhaps even an integrated tachometer.

It would be nice to hear opinions and stories, and to see pictures of what people are using to control their VFDs.

I would also like to get information on which parts you would recommend to use for the buttons, rotary switches etc.

It seems that in the industry, 22 mm (or is it 22.5?) or 30 mm modular controls are used. An "operator" is the user-facing part, and is easily replaced, while the body itself sits under the panel. There is 1 or more contact group (NO or NC) clicked into the body, also easily replaceable. It all sounds very nice, however it's quite expensive (a single complete switch can be around 20 EUR or more, potentiometers are usually the most expensive, running into 50-100+ EUR), and also there is a mind-boggling combination of parts available. I couldn't find an online shop that would present these parts in a way that is easy to comprehend. It seems one must study manufacturer's catalogs and then, knowing the exact part numbers required, order them. I understand these are industrial controls rated for high voltages and currents, adverse conditions, rough handling, and frequent usage for long periods. However, none of these concerns seem to apply in a hobby home workshop (and VFD control circuits use 24 VDC with very low currents). I'm sure the controls can also offer nice "feel", which is important, but is it worth the high cost? It just seems weird to spend more money on controls, than on VFD and motor (I got a used VFD for 50 EUR and a new motor for ~100 EUR). But if it makes for good user experience = happy working, perhaps it can be a worthwhile investment. If you like these controls and advise me to invest into them, can you recommend particular brands / model names, and shops/suppliers, and how to find all the necessary part numbers?

I've also seen significantly cheaper 22 mm push buttons and switches on eBay (from China), usually sold by vendors who sell all kinds of stuff and don't even have a proper store front. I didn't find it easy to find a matched/harmonized set of push buttons (start, stop, maybe jog), rotary switches, emergency stop button. If you had a good experience with such controls from eBay, AliExpress, or somewhere else, can you recommend sellers / brands / model names?

Considering that VFD control circuits are 24 VDC, many automotive switches (those rated for 24 VDC) could also be suitable, and they can be quite cheap. There seems to be such a multitude of those (many of them looking fancy, with various color LEDs, which I think wouldn't make sense on a lathe), that I don't even know where to start looking. Is this advisable? Can you recommend good shops / sellers?

Any advice on the potentiometer? The industrial ones seem to be crazily expensive, I'm thinking about just getting any regular single-turn linear taper potentiometer. The VFD I got (Yaskawa V1000) specifies a 2kOhm pot.

I wonder whether to install a tachometer display on the lathe itself, or on the control box.

Last but not least, what would be good for the enclosure, and how to produce a decent looking and durable legend?

[Neil WyattModerator @neilwyatt]

You might find the lower half of this article useful:

http://www.model-engineer.co.uk/news/article/3-phase-conversion-and-other-alternative-methods-of-powering-a-mini-lathe/18752

Neil

[Martin of WickParticipant @martinofwick]

You don't need industrial grade switch-ware for hobby use especially as it is only low VI stuff.

I get the cheapest and nastiest I can find by way of 22mm push button stuff or 35mm rocker/toggle switches from the usual fare eastern marketplaces. Ditto large rotary switches if you prefer these. I tend to go reasonably large as don't want to faffing about with 10mm stuff and micro switches. A big red button is always a comforting sight.

Search on 22mm push button etc…

A lot will depend on how you want to configure your controls ie press and release or switch etc. Also recommend getting push switches configurable as both NO or NC on the same block, gives you more options in case your VFD turns out picky.

For pots go for a sensibly large 1 turn wirewound 2-5 watt unit for mechanical robustness £2 to3 each or less in bulk via aliexcess. Avoid multiturn pots unless you enjoy a lot of twirling of controls – just my view.

I don't bother with decent looking – some sort of plastic box and label with my lidl Brother style tape labeller – sorry to be so unprofessional.

[SteviegtrParticipant @steviegtr]

I used to be an Electrical contractor & made many panels. I had accounts with wholesalers like Nyquist etc who stocked all the siemens buttons/ contact blocks etc. But now retired, Ended up buying Chinese cheapo's & up to now they have faired well. Look at the system I have. This is a cheap adaptable box, switches & buttons to suit. A cheap DRO. & a 10 turn potentiometer. Some say a 3/4 turn will do but I dispute & have accurate control over my speeds. Tell me a speed & I can set to it. With the 3/4 turn pot it is not easy to get accurate speeds. Most members say that does not matter. Only tonight I was running at 5 rpm to set some super glue on a item turning in the chuck. To finish it all off, find an engraver & get a nice panel front made. This one was £25. The difference between this & some dymo tape is chalk & cheese.

Steve.

Edited By Steviegtr on 03/03/2020 00:30:31

[Gary WoodingParticipant @garywooding25363]

I converted my Chester 12×36 Geared Head lathe to VFD some years ago. I wanted to be able to operate the machine exactly as before, but with the addition of a speed control knob. It has a control box which houses the wiring and relays that implement the NVR and motor forward/reverse functions. It was a complicated mass of wires and devices that seemed impossible to modify.

Modification for the VFD turned out to be very simple. The VFD output goes straight to the new 3ph motor, and both are outside the ctl box. There is a power lead that supplies 220v to the ctl box, so that was unchanged. I used a voltmeter to discover the power supply output from the NVR relay and used that to power the VFD directly. Nothing else in the ctl box was powered from the NVR relay. It was an easy job detecting which wires were used to activate the motor direction relays, and these were used to control the VFD. There was a jog button which I never used, so I replaced it with a suitable speed ctl potentiometer for the VFD, and made a suitable label for it. That was it. It was much easier than I originally thought.

Different VFDs need different speed ctl pots, so you will need to check the manual for your VFD.

 

Edited By Gary Wooding on 03/03/2020 07:49:57

[Ex contributorParticipant @mgnbuk]

16mm is also another option – used these for switchplates at my last employment as they are more compact than 22mm

Ebay UK supplier

has a variety of colours with a changeover contact (momentary action in this listing) – £3 each

22mm switch

another UK supplier for 22mm switches if the larger type are prefered – £4.05 each not too expensive ?

Nigel B

[Gene PavlovskyParticipant @genepavlovsky]

Thanks everyone for the answers so far. It seems that everyone advises to use cheaper Chinese 22 mm controls. Can someone recommend particular sellers, with something like a storefront / catalog on the topic? So that I won't have to mix and match controls bought from various sellers, who also sell a ton of unrelated stuff (and thus knows no technical details for their products).

Stevie, I saw a picture of your control panel before, I actually have it saved as (the) reference on the topic. It looks pretty nice. So are you saying all of these controls are cheapo Chinese stuff, including the pot? I've heard different opinions regarding single-turn (3/4) vs 10-turn, with most people advocating a single-turn. There are also 3- or 5- turn pots available, why not one of those as some kind of middle ground? I'm leaning towards a single-turn, although if buying cheap ones, I can't see any reason not to buy both and try what I like better. My VFD (Yaskawa V1000) actually has two analog inputs, and with two pots and suitable VFD settings, it would be possible to have coarse/fine speed pots (or maybe this could be achieved with just wiring, I didn't give it much thought – and I'm not an electrical guru). That tachometer display you have, is that one of the hall sensor + magnet + display kits I've seen on eBay for 10-20 EUR? Does it work well when running at the low speeds (such as 5 RPM that you mentioned)? I guess with one magnet it would take quite a few seconds for display to update?

Gary, your controls look pretty nice as well. Did I understand you correctly, that you have 220 V coming to your lathe, through the NVR switch, and then into VFD's power input? I don't know about your VFD, but the manual for mine doesn't recommend such an arrangement, in fact they say it's better not to power cycle the VFD more often than once in 30 minutes. It's better to have VFD hard-wired (possibly with a disconnect switch for servicing and maybe a magnetic contactor to implement some kinds of protections). Most VFDs have digital inputs for wiring start/stop and rev/fwd switches, with various arrangements possible (2-wire: on/off switch and rev/fwd selector, 3-wire: momentary NO push button start, momentary NC push button stop, rev/fwd selector switch). Even in 2-wire mode, VFD itself (with appropriate settings) prevents undesired restarts after power loss. Your NVR switch will also live longer when used this way (as opposed to full current at 220 V).

Nigel, thanks for the links. Those sellers might not ship to me (in Luxembourg), though. But I will try to find something along these lines. More links (with international shipping) will be very welcome I think I'll go with 22 mm as these would suit my large hands / fingers better.

Edited By Gene Pavlovsky on 03/03/2020 08:33:17

[Russell EberhardtParticipant @russelleberhardt48058]

I reused the switches that I took off my mill to make the control for the lathe:

Russell

[Ex contributorParticipant @mgnbuk]

More links (with international shipping) will be very welcome

I've had a quick browse on Ebay.de & Ebay.fr and at the lower end of the price scale most of the suppliers are the same UK based outfits as Ebay.co.uk & show free delivery to the EU – didn't check the particular suppliers I linked to, though, but probably worth asking them if their products seem the best option.

As ever, if you can stand the wait it is a lot cheaper to buy from China direct. Obviously the current situation will impact Chinese deliveries, but Hong Kong doesn't seem to have been as badly affected & items I have ordered from HK have arrived within the expected time frames.

Nigel B.

[Roderick JenkinsParticipant @roderickjenkins93242]

I took the easy way out, buying one of these kcAAOxy4XNSOXKm”>https://www.ebay.co.uk/itm/INVERTER-PENDANT-CONTROL-BOX-POD1-with-Estop-MYFORD-BOXFORD-DRILL-MILL/184153593092?hash=item2ae068d504:gkcAAOxy4XNSOXKm from ebay.

HTH,

Rod

Edited By Roderick Jenkins on 03/03/2020 09:27:41

[Martin of WickParticipant @martinofwick]

|……I didn't give it much thought – and I'm not an electrical guru)…..

Hmm… looks more like a bit of overthinking going on!

Through the advent of VFD control electronics, you have all the benefits of digital power switching, so use that to control the power side and use the wall switch to turn the VFD on and off. You don't need contactors, isolators, NVRs etc. and all of the old electromechanical crap from the past – the VFD takes care of all that.

The LV control side is about as complicated as wiring a 13A mains plug but less dangerous as it is LV!

 

 

Edited By Martin of Wick on 03/03/2020 09:47:58

Edited By Martin of Wick on 03/03/2020 09:54:18

[Gary WoodingParticipant @garywooding25363]

Gene,

My VFD (a Mitsubishi) is powered directly from the output of the NVR relay. When I first switch the lathe on from the wall socket, nothing happens. But when I press the Power Start button the NVR relay is energised and the VFD is powered up. The VFD then remains powered up until I switch the lathe off at the wall socket, or I press the RESET button.

Here's a schematic of the wiring – all the original relays except KM1 (the NVR) and wiring have been omitted for clarity. The speed ctl pot is a 3/4 turn version that I find is exactly right for my use.

[Gene PavlovskyParticipant @genepavlovsky]

Martin, overthinking is one of my favorite hobbies. I do, however, have a pretty good understanding of the wiring involved. In an industry setting, a VFD power input would still have an isolator (to disconnect the VFD when servicing/replacing is needed) and magnetic contactor (for wiring additional protection features), but I do agree that it seems unnecessary in a small home workshop. I plan to just attach a power cable with a plug on the input side of my VFD (+ an EMC filter), or maybe even hard-wire it if I decide to hang the unit on the wall. I have no questions regarding wiring, just about the "User Interface" and the individual components to use as buttons, switches, pots and enclosures.

Gary, I understand your wiring and the way it works is fine, as long as you don't hit the NVR stop button every few minutes . I just think that you could get rid of the KM1 magnetic contactor, and just wire the buttons connected to it directly to the VFD's digital inputs. On the other hand, why mess with something that works for you?

[Gene PavlovskyParticipant @genepavlovsky]

Is Jog a useful feature on a lathe? I guess it can be useful for screwcutting to a shoulder, or to an exact spot without a run-out groove, but on the other hand even better would be an automatic stop that trigger's the VFD fast-stop function. I plan to add such an auto-stop, in which case would Jog be useful for any other purposes?

[Neil WyattModerator @neilwyatt]

The 3/4 vs 10 turn pot (or anything else) issue is purely a matter of personal preference.

If you want to be able to set low speeds accurately and rapidly adust with a single turn then consider a log potentiometer instead of the linear one usually used.

Neil

[Gene PavlovskyParticipant @genepavlovsky]

Neil, I'll try the 3/4 turn first and see if it's to my liking, or not.

By the way, I have read your article and found it quite informational.

The part I didn't get is how did you set up your potentiometer's 0 setting to activate the jog mode.

Your wiring diagram appears to refer to the version 1 controls, with a separate switch for jog?

[SteviegtrParticipant @steviegtr]

Gene. No the slowest reliable speed I have seen on the DRO is 9rpm. When jog is active it runs slower than that. 1.5 Hz which is very slow. I tried to stop the chuck at that speed & found I could not. Actually amazed the torque from so low down. The motor is 1.5 hp. So that could explain something. The speed thing is definitely down to the user. I wanted to be able to run super slow for making & working on rings. When I am turning speed does not have to be so accurate. As Neil says it is down to preference. Hope it all works out. P.S the buttons /switches/ Dro all e-bay items. Even the potentiometer & dial.

Steve.

[Gary WoodingParticipant @garywooding25363]

Posted by Gene Pavlovsky on 03/03/2020 10:38:36:

Gary, I understand your wiring and the way it works is fine, as long as you don't hit the NVR stop button every few minutes . I just think that you could get rid of the KM1 magnetic contactor, and just wire the buttons connected to it directly to the VFD's digital inputs. On the other hand, why mess with something that works for you?

The only reason for hitting the NVR stop button is for an emergency, and it's location on the lathe control panel is very handy for such use. The KM1 output is at mains voltage so is certainly not suitable for connecting to the VFD digital inputs.

[Gene PavlovskyParticipant @genepavlovsky]

Ok Gary, maybe I misunderstood you. Is your emergency stop button a single unit with the KM1 relay/magnetic contactor? Or are they separate units wired together? If it's the latter, what I'm saying you can remove the relay and keep the e-stop button, wiring it directly to the VFD (it provides a 24 VDC power supply contact and digital input contact, the control buttons are between those).

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