So I recently decided to add a small feature to my casual simpit. Because I lack any real DIY abilities, I've opted for a "glass simpit" approach, where I use a 24" center-mounted touchscreen (together with Helios) for all of my switches and knobbery. It works well enough for most of what I want to do, especially with the fantastic Helios profiles that are available for Falcon 4 BMS, DCS A-10C, etc. Together with some simple printed overlays I've created for the Warthog throttle quadrant panel, I find that I don't really need anything more.
Except for one thing: the ejection handle. This is something that doesn't belong on the
HOTAS, and I hated to dedicate a precious quadrant panel switch to it. On the other hand, when you need to go, you need to go. I've had a decorative yellow-and-black ejection loop clamped to my seat for a few years, and I got it into my head to somehow make it functional. Turns out that it was much less complicated than I thought, even with zero electronics experience and very rudimentary construction abilities. So I thought I'd share with the group: this is a simple addition that only takes a few hours to make.
ELECTRONICSThe concept here could not get any simpler: pull handle, and send a joystick button press to the computer. Then, map that joystick button to the "eject" command in your sim of choice. All we need is some kind of USB interface board to emulate a joystick. There are a bunch of different alternatives for the beginner here. One is Leo Bodnar's series of boards (since we only need one digital button, the low-end button-box board will do). Another is to buy a cheap gamepad, crack it open, and harvest its board.
I ended up ordering something called a "Teensy++ 2.0", which is a fully programmable board that is about half the size of a stick of gum. Best of all, it's really cheap ($24), so you don't really worry too much about making mistakes. For this reason it's very popular among the "Maker" hobbyists.
You'll also need a switch to send the button press. I had toyed with a bunch of Rube Goldberg schemes, most of which involved pulleys, cables being tied to throw switches, one-ton Acme weights, and piles of birdseed. However, while browsing Sparkfun.com, I found a pull-chain on/off switch (the kind that you see on ceiling fans) for $1.50. This seemed to be the most direct way to implement the required pulling motion. However, I wasn't thrilled about the toggle problem -- because you pulled once for "on" and again for "off", I would somehow have to make sure that the chain was reset to the "off" position every time I started a new flight.
Because I had never soldered anything before, I also bought a breadboard to connect everything together. The Teensy went into the breadboard, and I connected one wire of the pull chain switch to one of the Teensy's digital input pins, and the other to the Teensy's "ground" pin. (These wires were of the stranded type, they didn't fit very well into the breadboard holes, so I had to use alligator clips to connect those stranded wires to a solid-core copper wire that I could jam into things.) Then I plugged a USB cable into the Teensy's onboard mini-USB port which automatically powered the whole thing up.
The Teensy board is fully compatible with Arduino, which is an open-source hardware platform that is very popular among the Maker hobbyist crowd. In English, this means that you can write these laughably simple "programs" and have them loaded on to the onboard memory of the Teensy. In this way you can write microcode that will cause lights to blink, inputs to be read, and signals to be sent. Arduino was intended for artists and designers and other non-techie types, so the "programming" involved is simple and painless. Using the included example code, it was easy to piece together a program that monitored the designated input pin: pull the chain once, and the pin read "1"…pull it again, and it read "0". Magic!
There was still the toggle problem, though. I didn't want the eject button to be pressed down with one pull, and released with another. Instead, I wanted an eject command to be sent every time the chain was pulled, whether it was switching from ON to OFF, or from OFF to ON. Here's where the easy programmability of the Teensy proved to be really valuable: I wrote some simple logic that would store the results of the last pin reading in memory. The next time the controller polled the input pin, it would compare the new reading with the old reading. If there was no change, the program did nothing. However, if there was a change -- regardless of 1 to 0 or 0 to 1 -- the Teensy would press and release the joystick button. This way, the physical toggle switch was converted into a momentary switch in software.
I took the whole unwieldy breadboard and plugged it into my gaming machine. Windows wouldn't recognize it at first, but when I reset the device setting to "Serial-Keyboard-Mouse-Joystick" instead of "Keyboard-Mouse-Joystick" (don't ask), the Teensy popped up as a game controller. Pull the chain, and Windows dutifully reported Button #1 on this controller being pressed and released.
But when I loaded Falcon 4 BMS, started instant action, and pulled the chain, I got a metallic click -- no good. I belatedly remembered that Falcon 4 requires three presses of the eject button. I added some lines in the Teensy code so that it would send not one press, but the required three presses (eventually I got the timing down so that it was 2 presses of 0.1 sec each, separated by two 0.1 sec releases, followed by a 2.0 sec press-and-hold…I think this is faster than I could hit CTRL-E manually). All of this trial-and-error was as easy as typing the code, plugging the Teensy in, pressing the "reset" button on the Teensy to reload the microcode, and then plugging the Teensy back into the simpit PC.
After about three hours of effort, the electronics worked -- pull the chain, and we'd hit the silk. Now I just needed to build the physical enclosure.
HARDWAREI did some measurements of the underside of my Obutto Ozone's seat, and picked up a few things from the store. First was a small plastic project box with a removable lid, from the local Fry's Electronics. The second was a 6" length of 1.25" PVC pipe, from the plumbing department of Lowe's. The idea was to arrange them like so:
First I drilled a hole in the lid of the project box.
Then, I used successively larger bits to widen the hole to 3/8", which was the diameter of the pull-chain switch. Oops -- wrong kind of drill bits for plastic. Tore a nice ragged edge into the desired hole. No matter -- stuff the pull-chain switch in there anyway, nobody will notice!
Next, glue the PVC pipe to the project box lid, centered around the hole. What kind of glue? Well, what kind of glue do we have? Gorilla Glue! Does it work on plastic? No idea, let's try it.
Seems to be sticking. Good enough. Set aside, let it dry.
In the meantime, I started my soldering career. Without getting into a lot of details, it was an inauspicious beginning. I was too ashamed to take pictures. Eventually I got everything stuck together that was supposed to be stuck together, without burning the house down. To cheer myself up I drilled another hole in the plastic enclosure. Yep, those are definitely the wrong drill bits. Oops.
So this is what the interior arrangement roughly looks like -- pull switch screwed (er, jammed) into the 3/8" hole in the lid, wired to the Teensy board, with USB plug leading out the side hole. I soldered the wires together (remember the stranded wire vs. solid-core wire?) and was so proud of the results I wrapped everything up in electrical tape. Electrical tape is fantastic.
Oh, right, I forgot to deal with strain relief or grommets or whatever for the USB cable. And how is the Teensy supposed to be secured? This is bad. Electrical tape to the rescue!
Quick, screw it closed before anybody sees. Shut up.
OK, here's the fun part. With the switch installed, the chain runs up out of the pipe, where we need to attach the pull handle. (The pull handle itself is a yellow bungee cord, wrapped in (of course) electrical tape, and cut to size). There are many reliable ways to attach a pull chain to something like this. I chose none of them. Instead: electrical tape.
Fine, but looking a little flaccid.
Fortunately I found some "rope clamps" at the Home Depot, which lends a nice mechanical illusion obscuring the fact that everything in this device is a big ball of electrical tape.
Nothing improves something like hitting it repeatedly with a hammer.
Here is what the assembly looks like installed. In addition to the rope clamps, I have affixed a horizontal metal plate to the back of the handle. The purpose of this plate is to keep the ejection handle from disappearing into the pipe, and at an appropriate height for convenient pulling. I considered many different ways to hold the device down against the upward pulling motion, including clamping it to the frame, placing spacer blocks between the top of the project box and the bottom rail of the seat, etc. I ended up using simple dead weight. It turns out that 8 lbs. is more than enough to keep the box flat on the floor. Right now I'm using a dumbbell (not shown), but am looking into a more permanent solution (maybe that will fit inside the box itself).
So, that's my latest improvement. I'm already thinking about the next one; since I've effectively circumvented the safety feature of requiring three separate eject commands to initiate ejection, it seems only wise to build a seat arming lever…
(this never ends, does it?)
