# Wiring A Vfd To A Momentary Pushbutton Switch (update)



## Eddyde

I just installed a Teco L510 VFD to run my mill. I wanted to use a momentary pushbutton "Forward", "Reverse" and "Stop" switch, However, the VFD requires the switch status to be constant, so  I designed a simple circuit using two latching DPDT relays to achieve the correct interface. I also made it so the latched relay will shunt the other relay, thus preventing the switch status from being in "run forward" and "run reverse" simultaneously. The VFD does have protection against that condition, but I figured it easy enough to do and it allows me to possibly  attach other things to the circuit such as indicator lights etc. 
I will be adding other features in the near future. One I am considering is a switch on the Hi/Lo Shift lever that would swap the forward and reverse relays so the directional pushbuttons will always be correct. 
I attached photos/video of the schematic (please excuse the sloppy drawing) breadboard testing, final build and installation.


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## kd4gij

nice job


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## derf

What is the advantage of a momentary switch?


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## Eddyde

derf said:


> What is the advantage of a momentary switch?


Well for me the main advantage is circumstantial, I had a couple of those NOS switches on hand. I also had all the other components so I didn't have to buy, and wait (the worse part) for, any additional items. I also feel the flush pushbuttons are less prone to accidental actuation or breakage (In fact, the original switch on the machine was broken). The other is I guess personal preference, I like the action and retro industrial look.


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## gr8legs

Actually, at least with the Teco drive I have, you can set the parameters to use momentary switches by appropriately setting the VFD system parameters.

I have a TECO MA7200 drive, so other Teco drives may vary but I'd think the control circuitry is the same.

To implement drive control with momentary contact switches get into program mode and click to System Parameter S-25. The factory default of 01 sets terminals 1 and 2 as 'sustained contact forward-reverse'.

Changing the S-25 parameter to 00 makes it momentary contact. Your 'Stop' pushbutton (N.O. contacts) then connects from 24VG (the same 'source' as for the 'forward' and 'reverse' ) to Terminal 5 which is designated a "Multi Function Contact Input". The supplied documentation is rather poor. You can implement any of the functions on any of the multi-function inputs by selecting the appropriate S- register 25 through 28.

Standard industrial 3-button switches use an N.C. switch for the 'Stop" button so that has to be reversed. There is a way to keep the same NC switch configuration but I don't want to unnecessarily confuse the issue.


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## Eddyde

Thanks gr8legs, for the suggestion.
However I don't think it will work on this model, I went through the entire manual,several times, searching for a way to change the switch parameters to momentary, because I thought "there must be a way". The only thing I found was a way to change the switch status from NO to NC... It only gives three choices; "Run Forward-Stop, Run Reverse-Stop" 2 switches. (this is the one I used)
"Run-Stop, Forward-Reverse" 2 switches.
and "Run, Stop, Forward-Reverse" 3 switches.
I cannot find reference to the parameter you mentioned in the manual either, Perhaps I'm still missing something? I would like to do away with the relay circuit, even though it was fun to build. I still have to wire my drill press to a VFD...


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## gr8legs

Yeah, your control is way different from mine and reading through the manual online I can't see a way to do it either. Sorry for the bum steer!

But at least it got me to looking at my Teco VFD control and figuring out how to make it work with 3 buttons. I like that a lot better.

Stu


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## KMoffett

I'm in the process of adding an auxiliary water-cooled, high-speed, VFD spindle to my mill. I wanted a box remote from the VFD to control the spindle. The box will have push-buttons for Power-ON, E-Stop, RUN, STOP, and a pot for the Speed.
Power-ON is separate from the mill's.
E-Stop is linked to both the VFD and the mill's E-Stop.
RUN is forward only, because I can never see using the spindle in reverse.
So, this is what I've come up with so far (attached).  I'm looking for switches for Power-ON, RUN, and STOP that I like.

Ken


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## JimDawson

Looks good!


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## Eddyde

Ken, It looks like a nice solid setup!
Thanks, Your schematic reminded to point out that I omitted the diodes across the relay coils in my circuit. I figured they weren't necessary for such small low power relays, it's all analog, no logic signals in out of the VFD and the circuit is only temporary till I do the CNC conversion. But anyone using larger DC relays or building for keeps should add them.


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## mksj

A while back I had a request for a design to use momentary switches on a VFD (TECO JNEV) that did not support 3 wire control. Attached is a schematic using momentary switches and latching relays that could be used on different machines that includes forward/reverse and stop. The left side of the relay is the VFD input controls, the right side of the relay is the latch. They are interlocked so you always need to go through stop to change directions. This was used on a lathe VFD conversion, also very simple and inexpensive. Not sure of the need for a relay coil diode for smaller relays and when using a separate power supply.


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## countryguy

As you transition the low power controller to hit the larger AC relays w/ inductive loading-  Just a tip that I was told was important w/ CNC controls.    Centroid really wants you to include snubbers on a variety of loads.  Good examples in the tip doc.      Love the post.  Good stuff!

http://www.centroidcnc.com/usersupport/support_files/tbs/tb206.pdf


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## stupoty

derf said:


> What is the advantage of a momentary switch?



Cant be accidentaly left in the on possition after a power outage,  appart from that i guess its just preferance.

All european stuff seems to have buttons appart from bench grinders which seem to have switches.

I do find it easy to hit the button if i need to stop.

I had factory installed buttons on my old 9x20 (cm) lathe but they were on the top, bad place to put them i reckon as you could lean on them accidentaly or drop somthing onto them, opps  .

Stuart


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## Eddyde

Okay So I redesigned the latching relay circuit to include an automatic reversing feature. It keeps the spindle rotation correct in accordance with the Forward & Reverse buttons when switched into either High or Low gear range. I had to add another relay so I just built a new board, I also added a terminal block. The status is sensed by a microswitch contacting the Hi/Lo shift lever. I know some eyes are rolling However. I will be converting the mill to CNC and this will let the computer will know the speed range its in. In the meantime, it will prevent bonehead mistakes, which I am perfectly capable of.







I also added a second VFD to power the Z Axis motor, and upgraded and relocated the Up/Down switch to the head, where it's more convenient.
One thing I discovered, if the Hi/Lo switch is actuated while the spindle is running the VFD stops then reverses. I can add a button in parallel, this will make a great tapping feature like the instant reverse button on the downed handle of a SIEG X3. Guess I'm not done yet...


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## tmarks11

Eddyde said:


> Thanks gr8legs, for the suggestion.
> However I don't think it will work on this model, I went through the entire manual,several times, searching for a way to change the switch parameters to momentary, because I thought "there must be a way". The only thing I found was a way to change the switch status from NO to NC... It only gives three choices; "Run Forward-Stop, Run Reverse-Stop" 2 switches. (this is the one I used)



The manual that came with my L510 is not complete.  It is missing chapters 6-11.  Some of those chapters have some good stuff in them.  Chapter 7 describes external control modes.  You can load it online at:

https://www.tecowestinghouse.com/Manuals/L510_instruction_manual.pdf

Look on page 7-3.  There is a diagram showing use of two momentary pushbuttons (one to start, one to stop).  Requires changing parameter 00-04=2.  "Three wire control mode".

So far I am not a happy camper (just got the VFD).  It gives my 2 HP a horrible resonance starting at 28 and continuing to 56 Hz.  Like shake my workbench vibration.  I have a 1 HP JNEV, and when I hook that up, the motor is smooth as silk.  Hopefully I can tune this thing a bit better, ow it is going back!


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## Eddyde

Yeah thats pretty much the manual I have, I know the switch configurations they offer but they didn't exactly fit what I wanted to do, hence my circuit. Hmm.. not sure why your getting the weird resonance, I have a 2 hp and it works fine, maybe it's a defect in that drive?


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## tmarks11

Eddyde said:


> Yeah thats pretty much the manual I have, I know the switch configurations they offer but they didn't exactly fit what I wanted to do, hence my circuit. Hmm.. not sure why your getting the weird resonance, I have a 2 hp and it works fine, maybe it's a defect in that drive?



I was glad I had a Teco JNEV on my shelf to test the motor out, otherwise I would have been yelling at the company I bought it from... came in a cardboard box split down the side, with the motor loose from the wood base it was bolted to and a shaft punched through the side of the cardboard. I thought "ohh no", and quickly hooked it up, and the dang thing just about fell off my workbench it was shaking so bad.

I will have to check if I have some 100X probes so I can hook my o-scope up and check the output.  All three phases are running the same voltage, but that really doesn't mean much.


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## Eddyde

A scope would certainly find if a phase had an irregular waveform or other anomaly. Please keep me abreast of what you find.


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## tmarks11

Well this sucks.

My JNEV gives me a nice shaped signal output on my o-scope, looks exactly like what I would expect.  My L510 gives me a real garbage looking signal, not surprised it is trying to shake the motor to pieces.  

Looks like I am going to have to RMA the L510.  I will take a closer look tomorrow just to make sure that I am not missing something.


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## amuller

Some VFDs support 3 wire control, some do not.  It seems an odd thing to omit but many do.  This is definitely something to pay attention to when buying a VFD, as very often one will want to use the existing push button station.


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## berniehernandez

You could use 3 wire mode, but you would need a Forward/Reverse toggle switch. You would have momentary run and stop buttons and a direction toggle switch. Your idea with latching relays is a good one for future use. We had a similar dilemma when we switch from hard button control to VFD control at work. Nothing a few relays could not fix.


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## tmarks11

Well I finally gave up on the L510.  I spent a couple hours on the phone with the Teco tech over a couple of days.  He started out really confident "The problem is parameter ###.  Check it and tell me what it is set to".  So I told him, and he was stumped, and it was downhill from there.  We tried a bunch of other stuff and it never got better.  So I shipped it back.

I upgraded to a Hitachi WJ200.  It was about $100 more, but I didn't want to go through the same pain again with another L510, and heard of a lot of happy people on the forum with one.

The WJ200 worked great out of the box, the motor is smooth all the way up.... even better then it was with the Teco JNEV that I had tested on the motor.  I think this will work out well.


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## berniehernandez

My postulate #23 :  If you can't make it work with minimal effort, send it back and buy another brand.


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## mksj

tmarks11 said:


> The WJ200 worked great out of the box, the motor is smooth all the way up.... even better then it was with the Teco JNEV that I had tested on the motor. I think this will work out well.


Let me know if you have any questions on the WJ200, I may be able to help. The manual is pretty poor, but the flexibility in controls is significantly better than many of the inexpensive VFDs and they seem to be very durable.


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## amuller

My experience is that some VFDs work with 3-wire control and some do not.  I have one, bought used on ebay, that is supposed to but it has special firmware and some of the features, including 3-wire control, are disabled.  It's always possible to build an interface with a transformer and a relay, but that is a pain.


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