We use a lot of equipment with contactors, and thus for one of my test units (a band saw) I connected the MAC to control the contactor via the contactors coil (current draw of the motor is to high for direct control of the motor power). However, even when I set the MAC detection at 1VA (1 watt) it will not detect the contactor coil current. The coil current flips between 1 and 2 on the MAC. How much current is required to be drawn before the MAC will detect ‘busy’?
Also, what is the length of time that a ‘busy’ signal when a relay is being used via the low voltage inputs (on display/control board) is required?
Thanks,
Roger
University of Texas at Austin, Texas Inventionworks
Thank you for your question. When controlling equipment with contactors, the Fabman Bridge device may not detect the current draw of the contactor coil alone, as the current is typically quite low and might fluctuate between 1 and 2 watts, as you’ve observed. This fluctuation might not be sufficient to trigger a ‘busy’ status detection.
To reliably detect whether the machine is ‘busy’ or ‘idle’, the Fabman Bridge needs to monitor the actual power consumption of the machine itself, not just the contactor. Unfortunately, when a contactor is used, the Bridge’s power detection is only seeing the coil’s consumption, which doesn’t represent the machine’s operational status.
There is, however, a solution for this scenario. You can find detailed guidance in our Help Section on how to properly connect machines via a contactor to a Fabman Bridge. This approach involves ensuring the Bridge can directly sense the load of the machine, providing accurate ‘busy’ and ‘idle’ status detection. Here’s the link to the relevant article: Connecting loads greater than 16 A or 3-phase machines. Check out the lower diagram in the article, which illustrates how the current sensor for buy/idle detection is integrated.
I hope this helps you resolve the issue with your band saw setup!