Solenoid Question

[Joe Fricke]

Please forgive my ignorance. I have some knowledge of control circuits, but do not work with them everyday.

What I am trying to do is add a simple on-delay timer (Fugi MS4SA) between a chuck closed button and the solenoid that actuates the chuck valve.

Problem: The manufacture of the pc. of equipment designed it so that if electrical power is lost the chuck stays closed. Activating the chuck close button on the robot removes power from the solenoid, not applies it. When the chuck open button is depressed the voltage is applied to the solenoid. Would this be called a normally closed valve?

One solution might be to replace the valve with a normally open valve, but the valve is part of a valve cluster specific to the pc. of equipment. Or abandon the original valve and change it to a 2-way 4-position valve?

I would rather not install a whole different valve. Is there a way to reverse the signal so that when the chuck close button is pushed 24V is applied to the timer instead of dropping to “0” volts?

 

[cowboybob]

Welcome to ETO, Joe Fricke!

The timer you listed appears to have a DPDT relay.

If I understand your query, you can achieve your goal simply by wiring the contacts of the relay appropriately.

But, I'm not exactly sure of the sequence of electrical events as they are now and how you wish them to be.

Could you give us a block diagram or a flow chart of these events?

 

[strantor]

What I am trying to do is add a simple on-delay timer (Fugi MS4SA) between a chuck closed button and the solenoid that actuates the chuck valve.

What is it that you want to happen? You want it so that the operator has to hold "chuck close" button in for a couple sec before it opens?

Problem: The manufacture of the pc. of equipment designed it so that if electrical power is lost the chuck stays closed. Activating the chuck close button on the robot removes power from the solenoid, not applies it.

Are you 100% sure that's correct? It doesn't seem intuitive to me. If what I quoted in blue is true, then what I quoted in red should read: "if electrical power is lost, the chuck will close in an uncontrolled manner."
I would expect to see a double acting valve with a blocked center. That way if power is lost, nothing happens with the chuck. If it was closed it stays closed and if it was open it stays open. Any uncontrolled movement in a deenergized machine is bad mojo.

When the chuck open button is depressed the voltage is applied to the solenoid. Would this be called a normally closed valve?

No way to say. Would have to see the pneumatic diagram. Chances are it's a directional control valve, and you could simply take the air line off the A port and put it on B port or vise versa.

One solution might be to replace the valve with a normally open valve, but the valve is part of a valve cluster specific to the pc. of equipment. Or abandon the original valve and change it to a 2-way 4-position valve?

I would rather not install a whole different valve. Is there a way to reverse the signal so that when the chuck close button is pushed 24V is applied to the timer instead of dropping to “0” volts?

 

[Joe Fricke]

CBB,
The timer is DPDT, but I'm not sure the solution is on the relay side. The pc. of equipment is a part picking robot. I believe that the control valve is a 3-way 2-position, but I'm guessing normally closed instead of normally open, because to close the chucks voltage is removed from the solenoid.

Cycle of operation is as follows.
1.) Robot moves to pick position.
2.) Robot triggers chuck close signal to solenoid. (The trigger is not a 24V signal, but removal of the 24V signal. The 24V signal is applied to the valve in it's normal state(chuck open.) I want it to be applied when I select chuck closed.
3.) Air valve switches and actuates the closing of the chucks
4.) Robot moves to drop position
5.) Robot triggers chuck open signal to solenoid. (Applies 24V)
6.) Robot chuck opens dropping the part

What I am trying to do is put a time delay in the circuit between the robot trigger signal and the solenoid. (See attachment for how I wired it.)
1.) Robot moves to pick position
2.) Robot triggers chuck close signal to On Delay Timer(Right now chuck close signal drops voltage to "0" which does not power up the timer.) The chuck open signal activates the timer. I need it to be reversed.)
3.) Timer counts down
4.) Timer relay closes contacts applying "24V" to valve
5.) Air valve switches and actuates the closing of the chucks
6.) Robot moves to drop position
7.) Robot triggers chuck open signal to solenoid. (Applies 24V)
8.) Robot chuck opens dropping the part

 

[Joe Fricke]

Strantor,
I've posted more detail.
The reasoning for how the robot manufacturer I am told is that if an electrical power failure occurs and the robot has a part in it's chuck it does not want that part to drop. This is not that important with the size parts I work with, but some of the parts this robot grabs and lifts high in the air if dropped could cause unnecessary damage. Regardless of the state of the valve, it will close when power is removed. Whether that is through the push button switch, through the logic, through the e-stop or through turning of the power switch to the whole unit.

 

[strantor]

Ok I get it.

The problem is that you're trying to delay the removal of a signal, after the signal has already been removed. This is going to require an OFF delay timer, which is more complicated and more costly than an ON delay timer.

This is going to be much simpler, easier, and cheaper to do in programming. Do you have access and knowledge to alter the robot's program? I guess not, or you wouldn't be installing time delay relays. So I'll move on to explaining the OFF delay timer.

Point #1: You aren't going to be able to use the robot controller's output to fire the solenoid directly anymore, because that signal disappears. You're going to need 24V straight from the power supply to the relay's contacts, out of the contacts to the solenoid.
The controller's output will now go only to the coil of the time delay relay.

Point #2: There are two kinds of off-delay timers. electronic and pneumatic. Electronic relays have separate terminals for power and coil.

• The electronic relay needs constant power because it has circuitry inside to control the timing and the relay switch. So 24v power straight from the power supply will go to the relay's power terminals and it's contact terminals. The the controller's output will go to the coil terminals; when the signal is removed from the coil terminals, a timer starts inside the relay, and when the timer runs out, it switches the output and cuts power to the solenoid.
• The pneumatic relays does not require permanent power to its coil terminals, but it does require permanent power to the contacts. The pneumatic timer's timing function is created by a spring-loaded vacuum plunger and an adjustable orifice. When power is removed from the coil, a mechanical timer (think sand in an hourglass) is started; the spring loaded plunger is allowed to start pulling a vacuum, and as air slowly passes through the orifice, the plunger slowly moves to the end of its stroke, and when the stroke is complete the switch contacts open.

Pneumatic relays are usually more expensive and I suggest the electronic option. But I only suggest the electronic option if it is absolutely impossible to make the very minor change to the robot programming. The programming change is the proper solution; the timer relay is more of a kluge.

 

[cowboybob]

Joe, this may be redundant (I don't have MS Office or Works) but...

This is just a first thought circuit. It's just for control of power to your timer if Electrical Power (EP) is lost:

EP "ON"

EP "OFF"

Am I on the right track, thus far?

 

[strantor]

Someone will probably come along and suggest that alternatively to the pneumatic or electronic relay, you could assemble a simple capacitor+resistor circuit to keep a standard relay coil energized for a short time. If you decide to pursue that, know that it is even more of a kluge than a timer relay to start, and in order to keep from damaging your controller output, you need to verify it can handle the high current spike when it switches on an empty capacitor.

 

[MaxHeadRoom78]

Isn't the valve a single unit mounted to a common manifold? if so it should be easy to change the valve type.
Or see if you can swap/change the output of the valve dependent on valve symbol shown on label as to its function, you could then change the function of the switch from N.O. to N.C.
Max.

 

[Joe Fricke]

CBB, you are correct. This is how it is working. I need it to work opposite.) Robot triggers chuck close signal to solenoid. (The trigger is not a 24V signal, but removal of the 24V signal. The 24V signal is applied to the valve in it's normal state(chuck open.) I want it to be applied when I select chuck closed.

Thank you all. It appears that I can use the same valve, just use an Off-Delay Timer function as Strantor suggests. It was also suggested by a former college to use a Smart Relay. ("That whole setup kind of sucks because the Star is reverse logic, meaning 0 volts is on, 24 volts is off. On the relay side if the logic states are a problem, get a smart relay from Newark. You can learn to program that in 5 minutes and set the timer and logic up anyway you want.")

I think either one of these I have here would work. Would you agree?

http://www.automationdirect.com/adc...l_Counter_-z-_Timer_-z-_Tachometer/CTT-1C-D24

http://www.newark.com/idec/fl1e-h12snd/smart-relay/dp/50R9725

 

[Les Jones]

Hi Joe,
It makes a nice change to have a clearly stated quesion. If my understanding is correct then connecting the delay timer to pin 4 instead of pin 3 on your existing relay should mean the timer starts when the robot removes power to the relay coil. When the timer times out its output relay will close. (This is an assumption as I do not know exactly how the timer behaves.) If you connect the solenoid valve via the normally closed contact on the timer then the power will be removed from the solenoid valve at the end of the delay period and the chuck will close. When the robot turns back on the signal to the relay it will remove power from the timer and the normally closed contact on the timer output will close and actuate the solenoid valve causing the chuck to open.

Les.

 

[strantor]

CBB, you are correct. This is how it is working. I need it to work opposite.) Robot triggers chuck close signal to solenoid. (The trigger is not a 24V signal, but removal of the 24V signal. The 24V signal is applied to the valve in it's normal state(chuck open.) I want it to be applied when I select chuck closed.

Thank you all. It appears that I can use the same valve, just use an Off-Delay Timer function as Strantor suggests. It was also suggested by a former college to use a Smart Relay. ("That whole setup kind of sucks because the Star is reverse logic, meaning 0 volts is on, 24 volts is off. On the relay side if the logic states are a problem, get a smart relay from Newark. You can learn to program that in 5 minutes and set the timer and logic up anyway you want.")

I think either one of these I have here would work. Would you agree?

http://www.automationdirect.com/adc...l_Counter_-z-_Timer_-z-_Tachometer/CTT-1C-D24

http://www.newark.com/idec/fl1e-h12snd/smart-relay/dp/50R9725

That idec smart relay requires a programming cable and maybe you have to pay for software too, not sure. It's overkill for this application.

The panelmeter from automationdirect is also overkill, and I would *assume* that you don't want people messing with the settings so you wouldn't face mount it on the panel, and since it isn't DIN-rail mountable, it would end up just sitting in the bottom of the panel, (which would look like crap).

The Fuji MS4SA that you have is only one P/N digit off from what you need: MS4SM. That's a multipurpose delay timer configurable for OFF-delay. It's only $48.50. Don't forget the $6.50 DIN rail base; this is an 11 pin relay; the 8pin base you got for the MS4SA won't work.

 

[Les Jones]

A timer like **broken link removed** on ebay may do what you want. It is designed for a 12 volt power supply but you could drop yor 24 volts to 12 volts with a LM7812 regulator or similar. The description of its operation is very poor in the advert but this youtube gives details of its modes of operation.

Les.

 

[Joe Fricke]

Thanks Strantor

 

[Joe Fricke]

Strantor,
I'm trying to lay this out but still run into problems. I am sure it is because of my poor explanation of how the current circuit works vs. how I would like it to work or my vast inexperience. As long as you aren't fed up yet, could you please continue to work with me.

The robot controller has two buttons Chuck Close and Chuck Open. When the Chuck Close signal is called for it latches the solenoid to a "0" volt state. When the Chuck Open signal is called for it latches the solenoid to a "24V" state. What I want is that when the Chuck Close button is called for it latches the solenoid to a "0"volt state after the timer runs out or once the Chuck Open button is depressed.

Looking at the Multi-Timer that you suggested it appears I need to do the following:
1.) Apply constant 24V power to pins 2 and 10 (I will pull this off of the robot power supply because the PS is plenty large enough)
2.) Apply a start signal across pin2 and pin 6 (In my mind applying a start signal requires applying 24V to pin 6, but because of the way the robot is programmed applying the chuck close signal drops the voltage to "0". This is where I'm stuck. That as well as the reset signal, and if it is needed.)

 

[Les Jones]

Hi Joe,
In statement 2 in post #15 you seem to be planning on applying 24 volts between pin 2 and pin 6. The documentation on the timer only shows closing a contact between pin 2 and pin 6. There is nothing to say that pin 6 is 24 volts positive of pin 2 when the contacts are open. I do not think it is safe to apply 24 volts to pin 6 as the signal could be some lower voltage. I think you would need a small relay whose coil is connected to the chuck close signal and connect a set of normally closed contacts on this relay between terminals 2 and 6 on the timer. When power is removed from the coil the relay contacts would close starting the timer.
Is my understanding correct that if the Chuck OPEN button is pressed before the end of the time delay then you want the chuck to CLOSE strait away ?

Les.

 

[Joe Fricke]

The IDEC SmartRelay has Off-Delay that appears to be triggered by a change from 24V to 0V state. Or maybe all that is needed is an inverter function? See attachment. At this time I think it might have been easier to upgrade the control valve to the 2 way 4 position valve and using the on-delay timer I already have here.

 

[MaxHeadRoom78]

What is the nature of the machine? Make etc? if it has a PLC type control for its I/O you may be able to change a rung or two, or is it all relay logic?
If so maybe you could post that portion of the schematic.
Max.

 

[Joe Fricke]

Les et al,
I get what you are saying about pins 2 and 6 now. The timer is looking for a dry contact closure to start the timer. Right?

On the Timer, Pin 2 and Pin 10 are coming straight from the robot PS to provide constant power to the timer unit.

As far as the relay, because of the way the robot manufacture designed the circuit, normal operation (Chuck Open) outputs 24V. The coil will be energized connecting C to NO during normal operation. When Chuck Closed is activated, the coil will de-energize connecting C to NC. Right? Therefore, I should connect timer pin 2(neutral from the robot PS to C and timer pin 6 to NO. NC on the relay should be left blank. On the contact side of the timer, jumper pin 1 to pin 2. Pin 3 should be wired to the common side of the solenoid. The hot side of the solenoid would be wired in parallel with pin 10(24V from the PS.) Thoughts?

 

[cowboybob]

The timer is looking for a dry contact closure to start the timer. Right?

That's the problem. The trigger for that device needs to be a positive going pulse, not a dry contact.

Joe, the circuit I posted is for providing the 24VDC when the "Chuck Open" button is pushed. This 24VDC could then be used to power up a "on energisation type One Shot Timer", such as this:**broken link removed**, in this configuration:

(snip taken from its the data sheet: https://media.digikey.com/pdf/Data Sheets/Crouzet PDFs/88827zzz.pdf, page 2.

Of course, you'd have to construct the circuit I posted, but I believe this arrangement would work for you.