Can a single output variable control two Relays?

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sakumar
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Can a single output variable control two Relays?

Post by sakumar »

Currently my "No Fault Out" signal goes to Relay OUT1 and that is connected to the C86ACCP no fault input.

I'd like to drive a second relay using the same signal (No Fault Out) to turn my spindle off in case of a drive fault. (The relay would indirectly turn the spindle off via a contactor.)

I can't use the same relay (OUT1) because the C86ACCP is 5V and the contactor is 24V.

The early spec. 8 Relay card had this feature that outputs 1 and 8 and 2 and 7 were tied together (so the output variable assigned to 8 would activate both 1 and 8) and that would have worked for me.

But now the 8 outputs are independent. I couldn't find a way to assign the same variable to two outputs using the wizard.

Is there a way that I can do that? If not, then is there another solution to my problem?

Thanks.
Richards
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Re: Can a single output variable control two Relays?

Post by Richards »

I've drawn a simple circuit that should work if I understand correctly what you want to do. The circuit shows how to use an Acorn relay output to drive an external contactor or relay. I'm using a generic DPDT relay symbol to represent a contactor. (The contactors that I've used are 3-Pole, Double Throw.) One pole of the contactor controls the C86ACCP circuit. Another pole of the contactor controls the spindle motor. The snubber diode shuts current when the contactor is turned off. When th NoFault output is ON, the contacts on the contactor close, giving power to the C86ACCP circuit and power to the spindle motor.

In this circuit, I have assumed that the Acorn Output is Normally ON and that the E-Stop or servo fault will turn it OFF.

NOTE: You already indicated that you'll use an additional contactor to turn the spindle ON/OFF. Just wire the AC power from the contactor in my schematic to the Common contact on the 2nd contactor. Wire the Normally Open contact on that 2nd contactor to the spindle. By doing that, both contactors must be ON for the Spindle motor to turn.



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Gary Campbell
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Re: Can a single output variable control two Relays?

Post by Gary Campbell »

Use the original NoFault relay to operate both the contactor and a single 25v relay that toggles 5v for the C86ACCP.
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sakumar
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Re: Can a single output variable control two Relays?

Post by sakumar »

Richards wrote: Tue Jun 22, 2021 8:10 am I've drawn a simple circuit that should work if I understand correctly what you want to do. The circuit shows how to use an Acorn relay output to drive an external contactor or relay.
Thanks! The unused ports on the contactor can be repurposed to both signal the C86ACCP in case of an E-stop and also turn off the spindle in case of a servo drive fault. Good idea.
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Re: Can a single output variable control two Relays?

Post by Richards »

Here's another schematic showing how I would control power to a motor with both the E-Stop switch and the NoFault output from the Acorn. Because the Spindle motor is controlled by two contactors in the schematic, the Acorn has to issue a valid NoFault output and a Motor On output before the spindle motor turns on. The left contactor turns on when the E-Stop is in its Normally Closed position AND the Acorn's NoFault output is active. IF the left contactor is ON and IF the Acorn issues a Motor ON signal to an output, the right contactor turns on and the Spindle Motor is activated.

I always use E-Stop switches that have at least two Normally Closed circuits. One of the circuits connects Ground to the Acorn's E-Stop input. The other circuit is put in series with the NoFault Acorn output to a contactor's coil. When the E-Stop is pushed, the Acorn is notified via its E-Stop input AND the current going to the contactor's coil is interrupted, stopping whatever it is that the contactor controls. In my case, the contactor controls voltage going to the servo power supply. I consider an E-Stop a real emergency. If I push the button, I want all axis motors to stop immediately. If the spindle motor were also wired through that contactor, I would want the spindle motor to stop immediately, too.

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sakumar
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Re: Can a single output variable control two Relays?

Post by sakumar »

I don't plan to use Acorn to control the spindle RPMs.

However, I do have an E-Stop. It's the unit that Centroid sells which has two separate Normally Closed 'channels'.

I've connected one channel to the E-Stop input of Acorn and COM. The other channel is in series with the OUT1 relay that is controlled by the NoFaultOut signal. (By the way, thanks for reminding me that I need to hook up the snubber across the contactor coil. I had bought one but forgotten all about it.)

That way the E-Stop can stop both the Acorn driven servo motors and the spindle.

The contactor enables the spindle power only if E-Stop is off AND NoFaultOut is asserted by Acorn.

Also, the two no fault terminals of the C86ACCP are connected to a (previously unused) Normally Open channel on the Contactor. So the spindle power and NoFault to C86ACCP are in lock step.
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Re: Can a single output variable control two Relays?

Post by martyscncgarage »

You can always drive a multi pole contactor with appropriate contact ratings for the load with your Estop Relay (Output 1)
Its what I do and what the Acorn System schematic depicts.

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Re: Can a single output variable control two Relays?

Post by Richards »

There's several philosophies about E-Stop switches. One is that the E-Stop switch should cut power to a master contactor's coil. The master contactor controls all power to all the electronics, using other contactors if necessary. Another is that the E-Stop is used in a boolean circuit along with a computer controlled output (NoFault is my choice for that output) so that both the E-Stop AND the NoFault output must enable a master contactor before servo power supplies, motors, pumps or any other auxiliary equipment can turn on. In this second case, power to the Acorn is independent of the E-Stop. That allows a two-step boot process. When initial power is turned on, the Acorn boots. After the Acorn has booted and is ready to control the electronics, it turns on the NoFault output. Then and only then, and only if the E-Stop has NOT been pushed, can all the auxiliary power and auxiliary devices turn on.

I use the second method. When I turn on the master disconnect switch, only the 24VDC power supply that controls the Acorn is turned on. When that power supply turns on, a green indicator lamp lights up to let me know that the Acorn has power. If the E-Stop switch has not been pushed, when the NoFault output turns on, the master contactor turns on and another indicator lamp lights up to show that the servos have power (as well as any other auxiliary devices). When I push the E-Stop button, the master contactor turns off but the Acorn stays on so that I can still see any error messages. With the Acorn still on, I can also see what line the Acorn was running when the E-Stop was pushed.

There are probably other E-Stop scenarios. I use the second scenario because I don't want any auxiliary device to have power until the Acorn is ready to control that device.
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sakumar
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Re: Can a single output variable control two Relays?

Post by sakumar »

Richards wrote: Wed Jun 23, 2021 12:25 pm There's several philosophies about E-Stop switches.

[...]

I use the second method. When I turn on the master disconnect switch, only the 24VDC power supply that controls the Acorn is turned on. ...
I believe I'm (mostly) using this method as well. I only have only one contactor though and its main job is to control the spindle and it also (now) connects the no-fault terminals of the C86ACCP.

When E-stop is pushed, power to the spindle is cut. The 24V power supply remains on so the Acorn and the Clearpath 24V powerhub have power. Pushing the E-stop also signals the E-stop input on the Acorn and I'm relying on that to stop the servo motors.

The slight difference is that the IPC-5 75V power supply to the Clearpath servo motors also has power during E-stop. In these forums, Clearpath support suggested that for better power/heat dissipation due to the sudden stop, keeping the power supply to the servo motors on is the better option.
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Re: Can a single output variable control two Relays?

Post by Richards »

Sakumar,
You're doing great. There are many different ways to connect components. The beauty of this forum is that we share ideas that show several ways to solve the same problem. Those of us who are pragmatic, think and experiment until we find something that works, then we stop experimenting unless we see that something still needs attention.

Your point about the IPC-5 power supply is excellent. Cutting power between the power supply and the motors when the capacitors in the power supply are charged can cause problems. AC induction is a real thing. Most of us have noticed that the old style light bulbs (before LED light bulbs became common place) would usually suddenly stop working when the AC switch was turned on or off. The voltage surge caused by the small amount of inductance in the filament was enough to break the filament. Servo and stepper motors have a lot more inductance than a light bulb's filament, but the principle is the same. If the motors are left connected to the power supply and you cut the AC power going to the power supply, then the motors' inductance is discharged through the power supply. If you cut the power between the power supply and the motors, bad things can happen.
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