The Evolution of My Annunciators

For almost two weeks, I have been working on printing, adjusting, and building three kinds of annunciators. The project began eight years ago with a plastic 3D-printed box with two LEDs, but it has now progressed to several designs that include a custom-made PCB.

I want to share the latest design for the Master Caution, Fire Warning, and Stab Out Of Trim (SOOT) indicators. This version was created utilising authentic components for reference, resulting in a product that closely resembles the original. However, I must disclose that while the front parts appear identical, the rear components differ significantly.

To provide lighting for the units, I used two 6x6x7mm tactile LEDs with a diffuser lens behind the main coloured lens. While filming the build today, we discovered why the OEM uses white filament/bulbs instead of coloured ones for a good reason. Our testing showed that achieving a completely even glow over the unit was impossible using coloured LEDs. On the other hand, white LEDs are the brightest and produce a diffused, evenly illuminated caption that relies on acrylic colour for the caption colour. Therefore, using a 120 OHM resistor with all captions illuminated by white LEDs ensures that the brightness of all captions is equal when they are all illuminated simultaneously.

I am pleased with the outcome of the illuminated switches. They are equipped with three pins each- Ground, LED, and switch- for operation. I utilized Dupont male header pins, but HX or JST can be used instead if you prefer a different pitch for your simulation. For secure attachment to the panel, each annunciator has a back shell. The only drawback of my design is that it lacks the same microswitch feel or click as authentic aircraft switches. While the real switches move 3mm, mine only moves 0.83mm before operating. Nonetheless, this may be a minor disadvantage.

Like the aforementioned annunciators, the Korry 318 Replica also features two led tactile switches that are mounted to a custom PCB with pre-soldered SMD diodes. This design allows for a push-to-test function or push-button operation, and a resin-printed body for a flawless finish. Once installed onto the 737SS MIP, they look incredible. To ensure that these multipurpose Korry function like the real thing, they feature four pins instead of the standard three.

Creating these units was a challenging process. The PCBs are quite small, as are the diodes, and fitting all of the necessary components into the limited space took several attempts. Ultimately, I decided to use prebuilt PCBs, which were more expensive but provided the best results.

The final design for today is the one in which I have developed two versions of the standard square korry, which is widely used in aviation. One is a dual-colour split-level Korry, and the other is a single-colour unit. The latter comes with a small PCB, which minimizes wiring requirements for the user's convenience.

This particular unit features four pins for connection and was initially created as a replacement for KD2 switches in my MCP designs. I had no idea that this design could be useful to other sim builders in various applications when I first released it. However, it has gained popularity, particularly among AIRBUS airliner builders who often order it in blue and orange. Additionally, I have used these Korrys in many different designs, including my Apache design, making it a versatile and multipurpose option.

All the necessary annunciator components are available on our webshop. We offer digital designs including STL and CAD files as well as PCBs for those who wish to create their own. Additionally, we provide all the electrical parts for DIY assembly. For those who prefer a pre-made option, we now offer a more expensive alternative for immediate use.

We have successfully completed this section of the MIP and it's time to move on to the next one. During the past few weeks, we have learned that while some units benefit from a PCB, not every situation requires it. In retrospect, using a PCB as a beginner is a wise decision rather than wiring hundreds of connections on an FMC. Moreover, it enhances the overall appearance of the sim, making it look more professional.

That's all I have to share in this blog post. As always, take care of yourself and feel free to contact me through our Discord channel if you need any assistance.

Karl