Due to limited space in the workshop, the suction device (Bernardo DC-400 400V) for the planer and table saw is placed one level above the workshop. The suction device is originally equipped with a zero-voltage switch (Kedu KOA7).

The suction device should be modified, such that it can be turned on and off directly from the workshop under the requirement, that any modification is only “inside” that device and that the device could be used elsewhere without any further modifications, too.

This led to the following solution:

• removal of the zero-voltage switch
• implementation of a self holding contactor circuit
• installing on and off push-buttons in the workshop.