Joystick control question

[nornrich]

All,

We produce a product that uses a small little brick PLC to control an AC Drive. The PLC and Drive both have a port for Modbus communication and I can eliminate some wiring in our system if we send commands across the bus. The issue I have is with controlling a joystick.

The drive allows a run command and direction command. With using a joystick to control the lifting platform I need to know how to hold and change the direction based on joystick control. If I hit and hold the joystick in the UP position until it hits a known switch this is easy, but there is a case when the operators might hit and hold up and then halfway they will back the platform down. Also if the operator releases the joystick I don't neccessarily want to change directions right away. The question becomes how do I determine when to trigger the reverse direction bit using the NO contacts of the UP and Down on the Joystick?

Regards,

Rich...

Richard Nornhold, PE

http://www.ovenind.com

 

[roydm]

Surely the joystick must have a central Off position.
If the operator lets go the joystick and it returns to the central Off position the drive should stop, or do you want the platform to carry on to the top limit switch?
In that case perhaps you could use a momentary lower to drop out the Up motion.
Either way you must include some means of protecting the operator in an emergency.
Roy