Inputs

Here are some exercises for the inputs.

First, we read the analog inputs: Turn the potentiometers on the PCB and observe the value reading on the I/O Monitor.

Remark: There is a delay between the activation of the input switches or potentiometers on the PCB and the reaction of the I/O Monitor. There is a lot of information to be transmitted for the refreshment of the I/O Monitor display in the EPOS Studio; hence, ittakes a while. Don’t worry, the internal state of the inputs are changed immediately.

Then, we configure and read some digital inputs.

Step 1: Set the purposes of digital inputs 1 to 6 as General A to General F. Set the

Mask to Enabled and the Polarity to High Active.

Step 2: Activate one of the digital inputs switches on the PCB and observe the reaction in the I/O Monitor.

Step 3: Change Mask to Disabled. How does this affect the reading of the input? Step 4: Change Polarity to Low Active. How does this affect the reading of the input?

Now, let's assign functionality to a digital input.

Step 1: Set the purpose of the digital input 1 to Negative Limit Switch and ExecMask to Enable.

Step 2: Activate digital input switch 1 on the PCB and observe the reaction of the EPOS and the Ready output.

Step 3: Clear the error in the EPOS Studio.

Step 4: What is the difference between Mask and ExecMask (execution mask)?

Finally, we apply this functionality: Use the digital input 1 to perform a homing onto the

Negative Limit Switch. Since you learned to perform a homing in chapter 3.2 you should be

able to do this without step-by-step instructions. How about the reaction of the Ready output?

Save parameters

Save the changed I/O parameters by right-clicking on the header of the I/O Monitor window. This avoids the loss of your settings in case of a power shut down.

Axis related input functionalities

Limit Switches and Home Switch

We have already seen what Limit Switches can be used for. They limit the mechanical working range on both sides. Very often inductive proximity switches are used as limit switches; if a metallic part comes in close proximity they change their output state. If a limit switch is activated the drive is assumed to have moved out of the permitted area. An error signal is generated; the drive comes to a stop and is disabled.

You can use one of the limit switches for homing after power up. No extra Home Switch is needed and it is clear where to look for it; at the corresponding positive or negative end of the mechanical travel. When using the limit switch for homing no error is generated of course.

For homing, you can also use a specially designed Home Switch and its input functionality.

Device Enable and Quick Stop

In most cases the enable and disable of the power stage in the controller is governed by the commands from the program in the master that controls the process. The Enable input functionality offers an additional way to control the power stage by an external digital signal: A rising edge with high active polarity on this input will enable the device; a falling edge will disable it.

This functionality might be useful in situations where you want to remove the power from the motor without referring to the program in the master. However, be careful, this feature does not comply with safety regulations!

The Quick Stop works in a similar way, but it brings the axis to a stop and holds the final position. The motor is still powered, i.e. the power stage remains enabled.

Capture Input: Position Marker

The Position Marker input records the actual position when this digital input is activated. A typical situation for this functionality is the

following: When an object on a conveyor belt passes a certain point (e.g. a light curtain) this is signaled to the motion controller on the

Position Marker input and the corresponding position of the conveyor

is stored. The process control program may now add the offset for the object on the belt to stop at a defined position.

Axis related output functionalities

Ready/Fault

The Ready/Fault output can be used to signal the correct operation of the device. Think of the common green and red light accessory on production machinery.

Trigger Output: Position Compare

Position Compare allows sending signals at a predefined position or

position intervals. This might be useful to activate another device or process by a digital signal if your axis moves through a specific position.

Best practice: If you want to see the output LED blinking on the EPOS Starter Kit, set the Pulse Width as long as possible, i.e. 64 000 s.

Holding Brake

Holding brakes are used to maintain a position without the motor being powered. This is useful to save energy in applications where the drive has to rest at the same position for a long time or where holding a position requires a lot of torque (e.g. on a vertical drive). Holding brakes hold position when they are not powered. Therefore, holding brakes may also be used as an emergency stopping device upon power shut down.

The powerful Holding Brake output allows the direct activation of brakes without additional power supply, taking into consideration the reaction time of the brake activation.

5 Alternative Operating Modes (optional)

Alternative operating modes allow running the motion controller without receiving on-line commands. Instead, analog voltage signals or signal pulses are used as command values. These incoming signals are converted to set values that are directly fed into the

corresponding control loop without a profile or trajectory being generated.

However, keep in mind that these operating modes do not correspond to the original intention of the EPOS product family, which is to be commanded on-line via a CAN-bus system from a programmed master device.