Quote from Hangar45 Admin on December 5, 2017, 7:45 am

(Original thread started on 02-28-13 by DonnyRay)

A Hangar45 member asked me how to get both sets of brake pedals to work in FS. While it is possible to wire up each brake pedal sensor to a separate analog input and scramble around with some offsets in software, it's much easier to do this in hardware.

 

The Lear45 braking system sums the input positions of all four brake pedal sensors. It looks at both "left" pedals and determines braking action based on which pedal is depressed the most. It does the same thing for both "right" pedals. If the pilot and the co-pilot are both mashing on the binders simultaneously the guy with the biggest feet has control of the brake signal applied to the wheels. If only one set of brake pedals are in use the LEFT and RIGHT sensors drive the brakes directly. This can be emulated with a simple summing network *because* the real airplane does this summation. It would be more difficult to model if the brakes operated in a different manner.

 

I have created a schematic of the dual-brake design that I used in my second cockpit.  Go to the bottom of this thread to download the PDF file.  Note that this scheme will *not* work with analog inputs that are biased. Most "game port" style analog inputs are biased inputs and will not work properly with this design. You need a true analog input with a minimum impedance of 100 kohms. Consult your I/O card specs for more information. 

 

NOTE:  Go to the bottom of this thread to download the L45 Dual Brake By Wire Schematic

 

(Posted by Ron Rollo on 03-01-13)

This is a very interesting approach to this problem and I would love to see this working in someone's sim someday! Meanwhile, what everyone is doing is simply running their four set of pot wires from their pedals to an interface card that can handle analog signals. Pokeys and Leo Bodnar cards as examples just to name a few. By using FSUIPC you can program as many LEFT brake pots and as many RIGHT brake pots as you want with no issues as long as you make sure of just one thing......

 

NOTE:  Before I get into the "one thing" that you have to make sure of, let me first explain that it is easy to connect up one set of pedals. You can't mess that up. In the next paragraph, when I compare the two toe brakes, I am talking about the pilots left toe brake and the co-pilots left toe brake. These are the signals that we are wanting to work well with each other. Same goes for the right toe brakes.

 

The only trick is to make sure that the pots are all facing the same direction so that FSUIPC does not get conflicting signals. In other words, one pot being backwards would be trying to put the brakes on and the other pot being correct would be at rest even though they are both physically at rest. If set up correctly, all the pots, (in our case four: left CPT, right CPT, left CP and right CP) should be at or close to 0 ohms while at rest. Then when either pedal or both pedals are pressed, FSUIPC picks up on it and applies braking.

 

If you are not familiar with FSUIPC, you will be by the time you are finished with your project!

 

(Posted by Randy Buchanan on 03-01-13)

It kinda makes me wonder why nobody ask me since the dual rudder pedal set I sent to Steve work with a USB. Plug and Play. And yes Ron the Leo Bodnar cards work great with the rudder pedals. What am I missing here?

 

I think it is funny DonnyRay that you would talk about both Pilot and Copilot stepping on the brakes at the same time. That should never happen because at that point neither pilot know what is happening. ie: Crash time. In real flying only one pilot is flying the plane. The manual always talks about communication between the PF (pilot flying) and the PNF (pilot not flying) and who is who at any given time. From the your very first lesson the instructor will make it clear to the student who is who by saying something like "I have it" or you've got it. By the way nice job on the drawing DonnyRay.

 

(Posted by Eric Tomlin on 03-01-13)

Hey Randy, this really has nothing to do with your pedal design, per se. What we have here is a retired NASA electrical engineer that has more time on his hands and a lot of "how to" knowledge/experience and if he's not coming up with something for me and Ron to take a second look at, he's not happy!

 

In this case, he has gone to the great length to design entire system logic for several aspects of our sims and is simply showing us how it is possible to create a true dual brake by wire system (and it's how his sim was made).

 

In your reference to one pilot not using the brakes when the other one is, well that's a given. But, what if there is a situation where it happens anyway, like in a real plane when there's either a misunderstanding or an impending accident, etc? The pedals being pressed the hardest are the most effective side and this is what he's made possible for others to replicate. However, you have to understand the mind of the DonnyRay- he builds his sims with more logic in there than almost any other home sim builder does. We're talking about entirely split electrical busses complete with real operating Circuit Breaker panels. This is the kind of stuff he designed for both the Shuttle and the ISS that's floating up there in space right now. It's in his blood and he cant help but to build his sim more and more complicated simply because "he can"!  He knows it drives me crazy, and he does a good job at it because I am one of those guys that LOVES systems. Just don't have the knowledge to implement like he does.

 

(Posted by DonnyRay Jones on 03-01-13)

No worries Randy. People ask me questions and I try to answer them.  Although.....I must admit....I'm not as much of a "regular" in Hangar45 as others. I'm retired from NASA but not from life. I have an active engineering consulting practice which keeps me busy. Many days I don't have time for simming at all so you won't find me here every day. But hey....I'm happy to help when I can.

 

My sim is more complex than many others because my efforts have been to model the real aircraft as accurately as possible. To the extent my time and budget allows my sim behaves like the real aircraft. FS does not model some aspects of the aircraft behavior and it models other functionality poorly. For example, there's no provision in FS for an APU that will keep the aircraft batteries charged. That's a big hole in FS, so I've built an APU emulator in hardware that is controlled via the pedestal panel and interfaced to FS via an I/O card. When my APU "runs" it prevents FS from draining the battery. (It also makes a fair amount of noise, as does the APU in the real airplane.)

 

I've used Phidget interface cards for all three cockpits I've built. I don't use game port inputs at all. The middleware that runs the Phidgets cards provides excellent functionality beyond that of most inexpensive I/O cards. Phidget cards are also USB devices, but they require that layer of middleware between the card and FSUIPC / WideFS if you want to insert hardware logic between the knobs and switches and FS. Since there are many things that FS doesn't do this allows me to extend the simulation to include things like the reverser interlocks in the thrust levers (throttle handles). Small solenoids in the handles prevent the use of reverse thrust until the squats are true, wheel speeds are up and the buckets have opened. I built that in external hardware and it drives the solenoids in my thrust levers in the same manner as the real aircraft.

 

Eric observes that my desire to model the aircraft in such detail drives him crazy. I suspect it's a short trip! Shoot...I suspect it's a short trip for all of us. How many normal people have a full-scale Lear cockpit in their house?

 

Folks are welcome to use any suggestions I post here - or not. The material I post is as accurate as I can make it, but it's not necessarily suitable for every builder. Some folks, like Eric, don't care about the APU. Many don't have real thrust levers or control wheels. I'll always try to post something that was useful to ME in my build and hope that others find some value in it as well.