Hi guys,
Does anyone know where I’d find the standard for Marker Beacon output interface? DO-143 doesn’t specify it and PS Engineering appear to have 7.5vdc +/-4.5v. Is it a 7.5vdc, 5vdc or other DC output? If any bright spark (excuse pun!) has avionics dimmer voltage range too that would be great.
DMEarc
This is from the IM for the 7000 and 8000 (both same)
which is completely nonsensical bull. I would read it as a pullup to an internal +7.5V rail.
However another approach is to look at some compatible interfaces e.g. the Sandel SN3500
which shows the output is indeed a pullup to an internal rail. The resistors are needed in case a lamp fails, to make sure the output level is close to GND.
I suggest you put in those resistors if you are using those outputs for anything.
Re the avionics bus dimmer voltage, that will just be what the lamps need. On a 28V aircraft the bus will be something like 15V to 24V, with 15V for the lowest brightness setting. If they have half a brain however they won’t go to 24V but will limit it to about 22V which will make “24V” lamps last about 10x longer. Socata use 16V – 21V.
