Introduction
As you may remember, I’ve created a case and backlight for the Hispapanel Miscellaneous panel of the F-16.
The MISC panel is located immediately to the left of the left MFD, hence, is accessible to the pilot by using his left hand. It control various systems, which can be summarized as Master Arm, and autopilot.
The panel is working great, but the well, quite intricated backlight led circuit prevent me to take advantage of low cost magnetic held switches, for this reason I chose to rebuild from ground the MISC panel. The panel update gravitates around the custom PCB I designed.
Panel disassembly
The first thing I had to do was to tear down the MISC panel, so to reuse all the components and clean the panel.
In the figures below the tear down process is summarized.
PCB design
The PCB embeds a 16 I/O satellite to be integrated with the pscockpit system. It comes with backlight led circuit based on SMD components, so lot less soldering lot less wires. It comes with the holes to fit the switches LED, and pushbuttons (RAFI 19H, and red button). The shape of the PCB has an offset with respect to the hispapanel and is 100% compatible with it. To design the board I relied on easyEDA, as the name suggest this web service is ultra easy, and allows to design a PCB starting from scratch, and taking advantage of a huge components library. To be fair I had to model the RAFI19H push button, with its pad/holes position and 3D model, but apart from that I just used COTS.
One of the features I appreciate most of easyEDA, is that it then allows you to share the project with jlcpcb, a great and cheap service to print the PCB, it also features SMD for very reasonable price (I took advantage of it to solder all the resistors and backlight LEDS). Just to let things clear, I’m a simple user of jlcpcb, I have no partnership whatsoever.
The board provides duponts connector for each switch, pushbutton or LED (with the exception of the RAFI button which is soldered directly to the board). Moreover it provides a couple of extra pins to be used with the low cost magnetic held switches.
Electrical layout
The panel is relatively simple, the only exception is that its components require multiple voltages (+5V for almost everything and +12V for the solenoid). For this reason a +5V source feeds the panel and microcontroller (as well as the magnetic held switch protection board), a different +5V source feeds the LEDS circuit, while +12V feed the solenoid.
Assembly
The assembly of the board was simple, as it is almost plug and play with the duponts connectors. In the pictures below, a couple of details of the assembled board.
The starting component are the naked PCB, almost naked, as they come with the leds and resistors SMD already soldered. The pass through component soldering is standard, and the relay protection circuit is simply plug&play. In the assembly I only took advantage of two layers of hispapanel plexi (namely the middle one and the engraved one), in this way the overall thickness is smaller, and the red pusbutton emerges a bit. The only component actually screwed to the panel is the ECM led light, while all the other are firmly secured on the PCB.
RC delay circuit
I connected to the MISC pcb the two magnetic held switches, having care of interfacing the relay board between the MISC and the solenoids. I configured everything in the pscockpit software, following this post (in particular, as briefly explained before, I configured the magnetic held switches as momentary).
When it came to the testing phase, everything was smooth both solenoids were working as expected. With a bit of surprise, when I ran the simulator, and was expecting both solenoids to be fired, only one was actually working.
This puzzling behavior made me believe that I’m really close to the limits of the system (either as far as PSU or boards power).
Psfalcon is a great piece of software but there is no option to delay an input, therefore I thought on adding an hardware delay. There is though the possibility to bind the switch position to the coil power. Unfortunately I could not take advantage of this option, as the coil is cheap, and if armed for a long time it will eventually break (in case the switch position is not reached). Anyway, as way around I designed a small pcb with a 555 timer delay circuit so as to make the digital signal to the solenoids last longer. The board takes advantage of two 555 IC, and a couple of NPN transitors (to invert the digital signal coming from the psfalcon software, which is normally low, while the 555 trigger expect a normally high signal).
A brief video of the effect of the timer delay circuit (in its breadboard version), on one LED (the other is fed directly with the pscockpit signal) is shown below.
The capacitor / resistor combination (470uF and 470 ohm), allows to have a ~0.2s long signal, enough to engage successfully the solenoids, even with the momentary coil option activated in psfalcon.
As a final note, the relay board only uses one ground for the input signals, it leaves one unused on the pcb board.
The additional ground can be handy in case one feeds the 5V and GND from a different power supply with respect to the psfalcon mainboard. So, to use the additional ground to connect it to the psfalcon mainboard, and provide common ground to the mainboard and satellite(s). You can find the gerber files in the repository.
Final assembly
For the final assembly I didn’t use any spacer, this allows to expose more the Alternative Release button. The panel /pcb stack is secured by means of a couple of M3 (black) screws and nuts. Finally I took care of adapting a bit the case (in particular in the lower part), so to ensure the (now bigger) panel.
Soon I’ll post some photos of the finished panel!
giovannimedici 
How is it going. I bought the MISC Panel from you and it looks great. Do you have a case for it? Or can you make one? I am building a makeshift pit and have the front panel.
Dear Erik, that’s unexpected 🙂 I don’t sell anything, I’d bet you bought it from hispapanels. No I don’t have a case for it. But I’m happy that your MISC panel is looking great !
Thanks