B737NG Overhead InterfaceIT I/O's POSTED!

This Forum is designed to support and assist in the use of any/all FDS related Interface products.

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Posts: 50
Joined: Fri May 06, 2005 11:24 am

Post by cdjung1 »


I've been reading the posts on the sys boards waiting for the right time to chime in. If there is anyone who had technophobia about being able to get the interface to work properly it is me. In fact I had been waiting patiently for a long time for something like this to come along. I have the Sys3 board and also ordered the Sys1 and Sys2 boards to completely wire my setup. I am through two full sections of the overhead and aside from my bad soldering skills (which are improving as I go) the interface part of making things work is as simple as everyone says. I initially had a couple of questions that I posted on the forum only to figure them out for myself before someone posted an answer. Peter is right that if you play with it a little you'll get it (and so far I don't have any hair on my palms). Using some simple logic and just a little experimentation I have been able to figure out how to hook up every type of switch. The downloadable variables are all there, it is just a matter of grabbing them.

One little tip to hooking up the rotary switches that might save someone some guess work. The center pin is negative and each of the poles around the outside of the switch represent a separate position on the rotary. It is just a matter of going into test mode and making sure that you connect the right pole before soldering. The only puzzle I have left to solve is the overhead metering panel and the FLT/ALT displays. I've seen other builders that appear to have that sorted out but my inquiries have so far been unanswered. If anyone has some ideas please let me know!


Posts: 504
Joined: Fri May 12, 2006 11:37 am
Location: Narvik, Norway

Post by vidarf »

Christopher, thanks for the lesson on wire gauges! :) Gotta love this hobby - something new to learn all the time!

Just a quick tip: you will save a LOT of grief and anger if you purchase a decent multimeter. Just don't go for the cheapest ones. Personally, I own a FLUKE 179, which covers all the usual stuff and has great accuracy.
The most handy function it has, is that it can beep whenever it reads a closed cirquit. This is great for rotaries, since you just place the switch in the desired setting, then go to the back and measure. Once you hear a beep, you're golden. :)

Would be a shame if you had to turn on the wipers to start your engines...

Posts: 504
Joined: Fri May 12, 2006 11:37 am
Location: Narvik, Norway

Post by vidarf »

Just wanted to put this in the "vault":

I got a question regarding the interfacing of the GEN BUS switches on the 737 overhead. These are momentary action in both states, not ON/OFF switches. There is only one XML file for the various generators, made for the ON/OFF kind of switches. Here's the solution:
This is where the InterfaceIT is a real beauty. You need to do this:
1. Assign the correct interface file to BOTH inputs. Let’s assume gen1 ON is connected to input #1 and gen1 OFF is connected to input #2.
2. For gen1 ON, delete the up / off action and leave it
3. For gen1 OFF, delete the up / off action and alter the value being set (2) to 0
4. Repeat for the other areas where this setup is used.

See what I do here? As far as the SYS card regards, the GEN switch is a two-way ON-ON switch, and you have to switch the generator on or off – or InterfaceIT will leave it as it is. All I did was to spread the function over two inputs, and tell the system: “If I select gen OFF, then set the bit to 0. If I select gen ON, set bit to 2. If nothing happens, do nothing. Ignore where the switch is.”

The same approach can be used on all switches with momentary function.

A good advice: When interfacing, have the system up and running. By hovering the mouse pointer over PMSystems, you will get the name of the variable. By altering the switches with your mouse, you will see the different values for that particular switch position.
Hopefully this will be helpful to someone out there. :)

Peter, shouldn't this topic be sticky'ed? :)

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