[Al_The_Man]

It was suggested that in a recent post I was talking over the heads of most members and guests here, so I thought I would explain a little deeper.
One of the things that started me thing on this track is the drawing EN-010 that is circulating for the G540 interface to a VFD, it shows a 20AMP relay to interface to a <10Ma input!
The accompanying JPG shows how to use a BOB etc that uses open collector bi-polar transistor or open drain Mosfet, as is done in the Gecko G540.
In place of the relay, it just entails a 2 wire connection.
Many VFD's have the capability of opting for sink or source inputs, the attached jpg shows a Huanyang which comes only sourced output, which requires a sink device such as the Gecko..


Also like many typical circuits that accompany BOB.s etc, the safety circuits leave alot to be desired, when compared to typical industry custom.
Very rarely is a typical E-Stop string used where the power is dropped to all motorized devices.
I am aware that most DIY CNC'ers tend not to worry about safety etc, but in the case of the EN-010 example, there is no means of emergency stopping the VFD whatsoever.
The G540 makes it difficult to remove power as the unit interfaces directly to the PC, so it is necessary for the whole unit to be powered in order for any external E-Stop to register with Mach, in this case.
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Further to the VFD shown, which appears to be a Huanyang, the user manual that came with the Huanyang I have shows the SPDT option relay as wrong, with the FB common and FC N.O. and FA N.C. whereas it is the opposite in fact on the model I received.
Al..