Hello this is my first post and forgive me if this isn't a relevant topic but I would appreciate and advice.

I have a 35 mm cinema projector that is driven by a 3 phase motor. As a 3 phase supply is not available I intend to run it from an inverter. The inverter has a digital operator built in but I would like to use external control buttons. In the past I have done this using a simple locking push button which when wired to the control terminals provides a run/stop function. However I would like to use the buttons that are part of the control panel of the projector. These buttons are not locking and are momentary contact. My question is what is the simplest way of providing a run signal to the inverter from this switch? I think asit is it will only run whilst the button is held in. Can I use a relay ? Thank you in advance.

 

That function should be built into any commercial inverter.

What is the model?

If it is not or you don't want to reprogram, there should be control voltage available to power external relay for stop/start control.

As a third option, a relay powered from the projector will work.

Wire control relay so momentary start button connects to relay coil.
Use one of it's own no. contacts across the start switch to latch it on.

 

Welcome to the forum.

These buttons are not locking

Are these separate buttons fo on/off respectively?
What voltages are on the buttons in the on and off states?
Do you want these simply to control the power supply to the inverter, or to interact with/over-ride the 'digital operator'?

 

You could use a relay picked up by the external MOM button to maintain the run contact on the VFD, if only needing FWD and no REV, you only need a single relay that latches in, the stop button would unlatch the relay, if the ext stop PB has a N.C. contact it would make it easier.
Max.

 

Thanks for responding its much appreciated . The VFD is an omron sysdrive 3g3xv. I'm not sure if this model has a built in 24v supply to power the relay? Other VFDs I have (omron j7) clearly does. I have found with this vfd that the stop start button when using 2 wire control, needs to be the locking type as a momentary contact will just run the motor whilst it is depressed. Forgive me for asking the basics but I am new to this , I need to use the sysdrive vfd as the j7 is not powerful enough. I don't need a reverse function just stop / start. The buttons on the projector , which for authenticities sake I would like to use , I believe are momentary contact buttons, how would I wire a relay into this arrangement to enable me to use these buttons to run the vfd and motor? Sorry if the answer is contained within one of your replies but as I said I am new to this and will appreciate any help or advice. Thank you .

 

The first thing you need to determine is, what power supply will be used to pull in a relay.

Then connect it to relay coil thru the momentary start switch.
So as when pressing switch, coil is activated.

Wire a contact of relay across the momentary start switch.
This will hold relay in, once switch is pressed.

If you follow that, we can continue.
As in a previous post. A normally closed contact on the stop switch will be needed to stop.

 

Like this............................
I couldn't find access to control circuit power for external use.

If it were mine and I understood the safety issues I might be tempted to try an scr control circuit. Which would only require a two wire control from 1 and 6.

 

If you look at Ch4 for 3 wire OP, it shows the diagram and timing for using a couple of P.B.'s, one N.O. one N.C. for stop.
Both momentary.
Apparently there does not appear to be an available supply on this VFD, but you won't need it if you have the two P.B.s available.
Is it possible to change the stop button for NC if it consists of NO?
Or are they membrane etc?
Max.

 

Thanks for that info, so just to clarify that means I don't need a relay at all ? I can just use the two push buttons? I don't know if the stop is n.c . - I will check.
Cheers

 

Thanks for that info, so just to clarify that means I don't need a relay at all ? I can just use the two push buttons? I don't know if the stop is n.c . - I will check.
Cheers

No relay if you can connect as per the diagram.
Are these discrete P.B.'s that can be changed out if necessary?
Max.

 

Thanks Max, no the buttons are part of a control panel that I would like to preserve . Thanks

 

You may need a relay to invert the stop PB if it is not N.C.
Is it possible to post a Pic of the P.B.'s?
Max.

 

Hi Max,
This is from the web if you scroll down the page to the 3rd pic from bottom you will see the control panel . Thanks again

 

Hi Max,
This is from the web if you scroll down the page to the 3rd pic from bottom you will see the control panel . Thanks again

Your img link is fail.

This is what he's referring to:

Pics of the outside of the buttons are not much help.

Can you access the inside of the panel?

Can you test resistance across the button contacts (with wires disconnected) for both start and stop and post the results here?

 

I am pretty sure I recognize those buttons, if so they are discrete buttons, especially the E-stop which is going to have a N.C. contact I suspect.
If not it may be possible to obtain the correct clip on contact module for the P.B.
If this is so, it should be relatively easy to hookup?
Max.

 

Thanks guys, not sure why image link didn't work but I appreciate you sorting it for me, I'm new here !

I won't have chance to physically access it until the weekend, am I looking for continuity on the stop button and no continuity on start with my meter, and the reverse when buttons are pressed ? If so will the diagram max provided from the manual work? Thanks for your help guys, very much appreciated.

 

In most cases the switch modules just latch on the back of the front operator, have either it labeled or have a colour code, green for N.O. red for N.C..
Either way you can check with a meter.
You just need the FWD and Stop if not interested in reverse.
Look to see if the switches have a manuf name, this would make it easier to confirm if you just need the contact assy.
Max.

 

Thanks Max, will do , i will get back to you. I found a circuit diagram (which is in Italian,) but it seems that the start is as you suggested, NC and the stop NO, I will try and scan it in and send it and also do as you suggest once i get my hands on the machine .