View Full Version : schematic help please

j king
12-27-2009, 09:37 PM
I am wiring ac drive up. The schematic shows this.http://img.photobucket.com/albums/v24/ikimjing/schematic.jpg

Do the stop and forward switch look like momentary switches? If so great.If not I need new switches.Thanks Jim

12-27-2009, 09:50 PM
Hi Jim,

The schematic is not very clear on this, but the description of the functions imply that the direction switch is NOT momentary. The run and stop switches appear to be momentary. There is probably a way to program the inputs to allow momentary switches to do what you want. For example, 3 momentary switches, 1 normally closed for STOP and 1 normally open for FORWARD and 1 normally open for REVERSE.

What VFD do you have (make and model)? I would be happy to look at a manual and point you to the right pages.


12-27-2009, 10:01 PM
If I read it correctly, my take is that none of the switches should be momentary.
The run switch shows NO (normaly open) and operates with the switch closed.
The stop switch shows NC (normally closed) and stops when opened.
On the direction switch, It shows forward with the switch opened, and reverse with the switch closed.

Others will correct me if I'm wrong.


j king
12-27-2009, 10:01 PM
It is an Omron 3G3MV. Thanks Robin.

12-27-2009, 10:05 PM
Clear as mud,the stop switch is a momentary with NC contacts like any other stop/start button.

The direction switch could be a maintained contact switch like a rotary or toggle.Pick the direction you want,then start?

Seems like it would be a PITA to use if both were momentary.

What does the previous page say or show?

12-27-2009, 10:13 PM
Maybe my understanding of a momentary switch is wrong, but I wouldnt want something that returned to its normal position when released for a stop switch.


j king
12-27-2009, 10:14 PM
What I have is a 2 position switch.Both N.O. This would give me my directions. As you rotate the switch further there is a momentary switch on both sides. This would give me the start that I need.Then all need is a NC switch for stop. I have this also.

Paul Alciatore
12-27-2009, 10:28 PM
First, this is not a schematic. Schematic diagrams are designed to show how the circuit works and this diagram clearly does NOT do that. It is a wiring diagram only.

That being said, as others have stated, it is not completely clear weather the start and stop switches are momentary or not. However, I would infer that the "NO" and "NC" designatons do suggest that these switches are momentary. These designations are normally only used for momentary switches. Also, it makes no sense to use two separate switches (the diagram does not show any linkage between the start and stop switches) that are not momentary. If they are not momentary, then either one could be used to turn the machine both on and off. And to operate with non-momentary switches would require the operator to turn them both on and off for each run/stop cycle. I would thefore would put the chances of them being momentary at least at 99%.

On the other hand, the forward/reverse switch which is NOT labeled with "NO" or "NC", would almost have to be non-momentary.

Paul Alciatore
12-27-2009, 10:33 PM
Maybe my understanding of a momentary switch is wrong, but I wouldnt want something that returned to its normal position when released for a stop switch.


Momentary switches are quite common for all functions when either electronic or relay logic control circuits are employed.

Paul Alciatore
12-27-2009, 10:36 PM
What I have is a 2 position switch.Both N.O. This would give me my directions. As you rotate the switch further there is a momentary switch on both sides. This would give me the start that I need.Then all need is a NC switch for stop. I have this also.

I'm not quite sure what kind of switch you are describing with, "What I have is a 2 position switch.Both N.O. This would give me my directions. As you rotate the switch further there is a momentary switch on both sides. This would give me the start that I need."

This sounds like it is a lot more than what is needed for the Start switch. A simple, NO (normally open) push button should be best.

Don Young
12-27-2009, 10:38 PM
I second Paul's thoughts. Only momentary switches have NO or NC designations. That is also how a standard push-button ON-OFF switch operates.

Don Young

j king
12-27-2009, 10:40 PM
Paul. That is what the direction switch looks like to me too. This is why I am hoping that the other 2 are momentary switches...

12-27-2009, 11:03 PM
From what I read, momentary switches are not used.

S3 states: Forward/Reverse rotation command. (Forward with the Direction switch opened, Reverse with the Direction switch closed.)

My VFD's also need solid switches, not momentary. I can reverse on the fly, by changing one switch.

But, I agree, that's not a concise diagram.

12-28-2009, 12:44 AM

I read and read and read again the manual for this drive and I am still not sure I understand it completely :rolleyes: . The switches appear to be maintained action only, no momentary allowed :confused: . Now on to actually setting it up the way you want.... You need to decide how you want to control start/stop and forward/reverse. IE: one switch for all or 2 switches, 1 for direction and 1 for start/stop. The easiest thing to try is to hook up the main power wiring and the motor connections then play with the control programming and switch functions with clip cords. This way you can keep the speed set slow for safety and see what happens when you do various things. As I read it you can not actually damage anything as long as the machine is clear and the speed set low. The worst that can happen is it might throw a fault and stop like it is supposed to.


PS: This thing has a very poor users manual :(

12-28-2009, 12:55 AM
The partial schematic uses the wrong symbols. They do not agree with the written description of each function as someone has mentioned. I believe both my Hitachi and Teco VFDs are the same, no momentary switches. Den

12-28-2009, 06:03 AM
VFDs usually have several methods of control. The page you have shown requires permenent contacts for start/stop. There will almost certainly be another mode that is edge triggered.

Edge triggered is the usual way to set up a machine tool, a momentary start button, momentary stop button (with any safety interlocks wired in series), a direction switch and maybe a jog button too.

You have to think a bit about safety. Machine tools are usually set up with a no volt release to ake sure they will not start up unnexpectedly upon power up. The VDF will have a setting to determine if it will run automatically upon application of power.

12-28-2009, 06:48 AM

I believe the wording used in the diagram is misleading.

The clue is in the symbols used for the switches - the run and stop switches use a very common convention of putting a vertical mark on the contact bar to indicate a momentary push switch.

(Which side of the bar and the colour of contact circles also indicates NO/NC)

The direction switch however is plain.



Marc M
12-28-2009, 07:47 AM
The Start & Stop are definitely momentary switches (it's a standard latched start/stop setup used on many, many machines)
The Direction switch is definitely maintained.

So, you need:
1 NO momentary switch
1 NC momentary switch
1 SPST maintained switch - could be slide, toggle, rotary, etc. your preference as long as it's maintained.

Marc -

j king
12-28-2009, 07:59 AM
well I will go out and start wiring with a temp. harness and see.. Thanks everyone! Jim
I gave up on wiring this thru the BOB and run it thru Mach 3. At the rate I am going I wouldnt get to see it run before I check out! Lol!!

12-28-2009, 08:57 AM
I think you need to tell us which VFD this is and ideally link to the Manual. I've set up two drives in the last couple of days, one an old Simovert and the other a new Huanyang. The Simovert was loaded with an almost random setup and the Huanyang pre configured for a high speed spindle (they're often sold as a package on ebay). Both needed me to go through the manuals very carefully.

I believe the wording used in the diagram is misleading.

The clue is in the symbols used for the switches - the run and stop switches use a very common convention of putting a vertical mark on the contact bar to indicate a momentary push switch.

The manuals often use generic diagrams, so I wouldn't put much trust in the symbols. I think you could be right though and it is describing a latching setup (start on rising edge, stop on falling edge), but there may well also be a non latching setting as well.

12-28-2009, 09:10 AM
The Diagram is very clear.
The Stop, Start switches are momentary and the Direction is not.
Tom M.

j king
12-28-2009, 09:10 AM

Posted the make and model. I cant link the manual online because the only thing I found was in Spanish! I contacted Omron and they emailed the English version.

12-28-2009, 09:17 AM
User manual here:-




12-28-2009, 09:18 AM
I read it as the Stop/ Start are momentary buttons/switches. The S2 input is simply a run enable and the S1 input is the run/seal in. As long as S2 has an input (indicated by the NC switch), the drive is enabled to run. It is simply a permissive. A momentary voltage applied to S1 through the 'Run' button initiates the run, and the drive seals a contact to maintain the run internally. Loss of voltage to S2 (momentarily opening the 'Stop' button or a power loss), drops the seal internally and then resets the drive state to 'enable' again when the 'Stop' button is released or the power is restored. Seen a lot of drives this very way. The theory is that ANY loss of power would drop the drive out and the machine could not re-start without a new operator input. That part of the diagram is probably drawn correctly.

You are on your own with the direction switch. But logic would dictate that with a voltage applied to S3, the machine would run one direction. The loss of voltage would reverse the direction- all done internally. I would therefore try a maintained switch first.

j king
12-28-2009, 10:55 AM
Once again thank you all. I couldnt have ever got the toys working without everyone's help. I truly mean this.

Drum roll ..buddadadadadadaaaadaaaaa Ding! It works. The momentary switches do as some replied. Now to run to town to pick up a pot switch. I have a really nice one but it is physically too large. Dang it..

I would like to wire this to the B.O.B. someday but I can live with this being manually operated for a long time. :)

Big thanks, Jim

12-28-2009, 11:17 AM
You appear to need the following:
- one momentary normally open pushbutton switch for start
- one momentary normally closed pushbutton switch for stop. A latching
e-stop style switch will probably also work, but you would need to release
before hitting the run button.
- one SPST toggle switch (non-momentary) for forward/reverse or
any other switch such as SPDT, DPDT, etc. which can serve as
a SPST switch. A rocker switch can also be used.

However, that diagram is crap, and you should test using clip leads or similar (as described below) before wiring up a control panel. Text and symbols are somewhat inconsistent or ambiguous.

The symbol for the start switch is the symbol for a momentary N.O. pushbutton; it is also marked NO. The text, however suggests that the connection might need to be maintained to continue running but is ambiguous.

The symbol for the stop switch is the symbol for a momentary N.C pushbutton and it also says "NC".

The symbol for the direction switch as used is ambiguous garbage. In some schools (US electrician), this could be a symbol for a SPST NO double break contact. Single vs double break is completely irrelevant here. The single break SPST symbol (two circles with a diagonal line from one circle to a point not touching the other circle) would have been much more universal and more appropriate. The text indicates that you need a SPST style switch. A momentary pushbutton would not make much sense here. And the text is pretty clear that the motor runs in reverse when this contact is closed and runs forward when it isn't.

If you would prefer to use an e-stop style latching NC pushbutton switch, you might be able to make it work by using a jumper in place of the run (start) switch. Any decent control would make stop override run, but the text is not clear on this and the wiring shown has stop basically interrupt both run and stop inputs.

Do the following tests in the order indicated and do not change anything except where these instructions say to. I.E. the state of the clip leads remains constant until explicitly changed. Be prepared to disconnect power in case you need to stop the motor and the control does not behave. You will need three clip leads.
Put four little pieces of uninsulated solid wire on S1, S2, S3, and SC that you can connect clip leads to. Bend them so they don't touch each other (or any metal objects) even with clipleads connected. If you need to, use 4 longer pieces of insulated wire with the ends stripped so you can get more separation. You may connect one end of each clip lead to SC and leave that end connected for the duration of the test.

Set parameter n052 to 0 using the menus, if you haven't already, to select the operation mode that corresponds to the diagram you selected and posted here.
Connect a clip lead from S2 to SC. Leave it there.
Connect a second clip lead from S1 to SC. The motor should start in the forward direction (assuming you don't have motor leads in wrong order).
Disconnect the clip lead between S1 and SC. The motor should continue to run.
Pull the clip lead connecting S2 to SC. The motor should stop.
Reconnect it (S2/SC). The motor should not restart.
Connect a clip lead from S3 to SC and leave it there.
Now connect a clip lead from S1 to SC momentarily, then remove. The motor should start in the reverse direction and continue to run.
Now disconnect the clip lead on S2. The motor should stop.
Disconnect S3 from SC. Connect S2 to SC, leave it there. Connect S1 to SC and leave it there. The motor should run forward.
Disconnect S2 from SC. The motor should stop. If it doesn't this means that STOP does not override RUN. In this case, disconnect S1 from SC to stop the motor.

If these tests are successful, you can use the switches as indicated at the beginning of this message as shown in the diagram. You can also wire the three switches between their respective inputs and SC and ignore running the run switch through the stop switch as shown in the diagram unless the last test failed.

There may be a way to configure the control to use a momentary N.O. button for STOP, since that is what you already have, but the switch would also need to be wired differently than shown in the diagram.

Paul Alciatore
12-29-2009, 08:45 PM
I'm glad it's working.

12-29-2009, 10:51 PM
Glad its working, and thanks to those that pointed out the errors in my thinking, from which i profited too.


12-29-2009, 11:56 PM
I don't believe it's been mentioned... but in a "three wire system" one of the advantages in using a NC switch for stop is that it's inherently fail-safe in case of a cable break or a dirty switch. The unit will not run unless the "stop" circuit is complete. In the vfd case, this control system is mimicing what has been around for decades with magnetic starters.

Although most VFD installations allow either the three way or the three position switch for fwd-off-rev, I always set them up for separate momentary stop/start. IMHO.. safer... and often wire in a separate EPO latching "large head" switch.

j king
12-30-2009, 08:21 AM
The bad thing about how I have it set up is that the stop isnt wired thru the e-stop. If I use the e-stop the spindle will continue to spin. Someday Ill get that fixed I hope.. Jim

12-30-2009, 12:19 PM
With a VFD it's common to use different inputs for "stop" and "emergency stop".

In a normal stop situation, the mill decelerates the mill under power. In other words, if you have a 3 second deceleration programed, the motor will develop power through that time. In an emergency that can often be bad.

An "Emergency stop" usually cuts all power to the motor. If nothing is impeding the rotation, it will "free wheel" to a stop. Emergency stop buttons typically latch down (i.e., not momentary), and the button has to be physically deactivated (i.e. pulled back out) before the machine can be restarted.

12-30-2009, 01:04 PM
E stop functions are different depending on the VFD manufacturer.

The Teco/Westinghouse E-stop function is a one shot meaning if you use a momentary NO switch and it closes, even for a moment, the VFD displays "E-STOP" and the VFD cannot be restarted until you press RESET on the front panel and the switches are in the STOP position. Some use the Base Block function as an E-Stop.

j king
12-30-2009, 01:14 PM
When I say the spindle will continue to spin I mean that the ac drive is separate from mach 3's control.f I hit the estop the spindle will not see that.I wired the ac drive to be manually controlled.

I am sure there is a way to hook it together even if it isnt driven by mach but I am really tired of messing with stuff I cant understand. Makes my head hurt.

: () jim