Stepper motor control with UID-0808THS

[Mark P]

I’m working on a Unistream application using UID-0808THS modules to control stepper motors on an XY table. I have the moves working and the machine sequences through the preset positions but I have an issue with homing.

The homing function woks fine, when initiated to set the current position to zero, or whatever offset is used, but I need someway to move the motors to a position that is the home position, or an offset from the home position, before initiating the home function.

This could be a programmed sequence that goes to a switch input, or a manual jog type function that would allow the operator to move the table manually and then set the home position when it is in the correct position. I can’t find any way to get the motors to move other than the relative or absolute moves on the PTO Move function.

Any help or suggestions would be appreciated.

Thanks, 

Mark 

[kratmel]

In general, I imagined the process of moving to the home position as follows.
1. Configure the axis as in the PTO example for jog mode - that is, slow movement from an external signal (Go home bit) for a distance greater than the length of the linear axis.
2. Check whether the home position sensor is activated.
3. If so, move in the opposite direction until the sensor is turned off and then move in the this direction for some time (or distance) - "Retract from home sensor" mode
4. If the sensor is not activated (or the movement described in point 3 is performed) - set the intermediate variable - Go home bit  movement to the home position ( slow Jog move to home sensor used).
5. With the help of this bit, we activate the jog movement towards the home position. This bit is deactivated by the home sensor signal. At the same time, a quick stop of movement to the home position is activated.
6. After a complete stop (velocity =0 or after some time) - the intermediate home position is established by the PTO command for define HOME.
7. Next, the position movement (absolute or increment again configured) is carried out by some value defined by the parameter in the opposite direction from the home sensor in order to move away from it.
8. After stopping this movement, the PTO command for setting the zero position is activated again and only then I can say that the mechanism is in the home position. (Home sensor now can be used as End Sw).

P.S. Maybe someone use different sequense - than please post used solution to this topic

[Mark P]

Thanks, Item 1 in your reply was the most important, after looking at the jog example it made everything easier. Once i could jog the motors the homing sequence is pretty simple, and I have used one of the existing over travel switches. A bit more testing to do but seems to be working fine.