Hi,
I'd like to optimize a DMX (RS-485 variant) input and output.
I was thinking to do the following:
Inputs : * Optically isolated * 120 ohm (switchable) * PTC in series with the 2 signals (EPCOS A707, Itrip = 90mA, 125 ohm) * 7,5V Transorb diodes after the PTC to the ground (SM6T7V5A)
Outputs: * Not isolated, ground connected with 100 ohm to the circuit ground. * PTC in series with the 2 signals (EPCOS A606, I trip = 180 mA,
27 ohm) * Same transorb diodes as inputs.
It seems obvious to me to put a 120 ohm over the output to, but i do not see this in other designs. Should i do this???
What is the most common was to implement a 'fool proof' DMX interface?
Regards.