[TowerTalk] STEPPIR QUESTION

[Rick Stealey]

>
> Providing protection for the driver requires a circuit that limits the
> output current on every line

Nice work Jerry.  I don't completely understand all, but it sounds to me as if you are saying something like the lines (i.e. pins 1-2, and 3-4 going to the driven element) 
are balanced.  Meaning no current is returning on ground?
To provide some means of lightning protection on the control lines we need to consider two scenarios.  One is to protect the 
controller, specifically the driver chips.  The other is to "keep the fireball out of the house",  meaning keeping surges from getting to the controller where they can work their way to other devices such as a transceiver connected to the data port.
So, in the latter case, it seems to me MOVs across all conductors to ground, placed on a SPG at the house entrance, would serve that purpose the same as a rotor protector using MOVs, or gas tubes on the coax lines.  
The question is, do those MOVs protect the driver chips, due to their bridge configuration?  And if the MOVs should short out after doing their job, does the controller then destroy itself due to seeing a direct short to ground on one or more of the output lines?
What about MOVs across the motor windings (pins 1-2, 3-4, etc of the DB25)?  to protect the chips.
Incidentally, MOVs rated at 39 volts are available for 45 cents at Mouser.  They are rated for huge currents, 2000 amps if memory serves me correctly. 
Rick  K2XT


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