The latest tasks spreadsheet is up. Alhough some testing/debugging remains, the highlight is completion of building the panel. After moving a couple of non-essential tasks to later sections, there are now just seven (7) build/install items left to complete before first engine start. Of those seven items, three (3) are more than 50% done already. Progress happens!

The latest editions of the remaining tasks spreadsheet and electrical spreadsheet are in the Checklists and Design, Electrical subsections of the Library, Project Documents collection.

The task list reflects good progress on items before first engine start as well as significant progress on tasks before inspection. The electrical sheet has lots of new stuff, primarly additional interconnect detail which frankly, is a bit of a crutch to hang onto data necessary for final schematics... which will get done at some point. In the meantime, essential keys to that puzzle are in the tables of connections.

The electrical spreadsheet has become more than a repository for just electrical info, and now includes a growing number of things like tips on installing and/or removing panels and other components, equipment serial numbers & install dates, etc.

After fielding several questions about how and why the LED indicators on the panel were designed and built as they were, I decided to write a small article to answer these questions. It's a work in progress and will have more pictures later on... but for those who may be curious right now, the whole scoop, including part numbers and sources, is in the Library.

 [...a work in progress, as I plan to add more photos, etc.]

Friend and fellow Rebel builder Terry Dazey was the latest of several people to inquire about details of the LED indicators. My response below covers most of the details of the why, what, and how. Terry asked:

Maybe I missed a link in your web Rebel photo description, but I am curious what is the part number and where did you purchased the small, colored LED annunciator lights as shown on your left wing panel? I like 'em.

Well, that's a story. After way too much cogitation and research, and after trying several things, I ended up with the design and parts I did because I had the following requirements:

A) I wanted a semi-flush appearance, B) I wanted wide angle visibility, C) I wanted a couple of the LED's to be self-blinking, and D) I wanted them to be replaceable, because even LED's do sometimes burn out.

Although these goals were met, the tradeoff, at least as I did it, was to give up getting out-of-the-box-robust mechanical strength, and I had to beef up the parts I has chosen with lots of heat shrink. In detail....

First, the basics: in a nominal +12 VDC circuit (more likely north of 13.8 VDC with an alternator running) an LED must have a resistor ahead of the LED, in series with it, to act as a current limiter. Without the limiting resistor, the internal resistance of an LED is too small to self-regulate at that voltage, and excess current will promptly burn out the LED. LED's come in different colors, which are derived through use of different elements (metals and minerals) in the LED. The current handling (internal resistance) characteristics of the different materials also vary, which means different colors of LED's will often require different values of external resistors. Common values range from 470 ohms to 1K ohms or more.

A bare LED has small stiff wires coming out of a plastic bulb. The wires are fragile, and can be easily broken off where they enter the hard bulb. It's not easy to solder resistors on one of these wires without breaking it, or overheating the LED, much less solder a longer wire onto the resistor. Consequently, manufacturers have come up with various standard, and not so standard ways to mount the fragile LED wire leads, including use of external ceramic "sockets" into which the bare LED wires are plugged, and encasing the whole thing is a larger volume of plastic, etc. In addition, there are different ways the physical mounting or encasing can be built to include the necessary (at 13.8 VDC) resistor. Most amateur builders will not buy bare LED's, but rather one of these kinds of preformed, pre-wired LED assemblies that include at least a resistor and extended wires. [See photo below for views of the parts I used, as well as a couple alternatives.]

I used the preformed "hobbyist" 5MM LED assemblies available in various colors from SuperBrightLEDs. The trouble with those is mechanical -- the resistor is soldered right onto one of the stiff and fragile LED leads, then attached to longer flexible stranded hookup wire. The resistor and hookup wires continue to hang onto the very fragile junction between themselves and the glass "bulb" of the LED -- there is no external casing to cover and connect both the bare lead, and the resistor and stranded hookup wire extensions. Until the LED assemblies I chose are beefed up with multiple layers of heat shrink, such that I could finally enclosed both the mount (see below) and the heat shrink laden wires together as one unit -- the fragility remains. SuperBrightLED's pre-wired LED assemblies include blinking RED ones. (http://allelectonics.com also has blinking ones in other colors.)

Now for the assembly. Looking at the edge of the panel, with the finish side to the left, and proceeding left to right, first there is the plastic, cylindrical (Fresnel) lens, cylindrically shaped with one end open. The lens "cylinder" goes through the panel opening, and snaps in place. On the back side of the panel, a white plastic ring "spacer" is slipped over the lens barrel. It's sole purpose is to take up space. (See photo below) Then the LED assembly (LED, resistor & extension wires) is gently pressed into the back of the lens barrel. Fnally, the black plastic ring retainer is press fit over the wires and the last part of the lens barrel, and clamps the lens around the LED body, locking it in place so it won't slide out of the lens barrel. Additional layers of heat shrink are then added carefully, until the fragile leads are protected all the way from LED body to the extended hookup wires. It's good to order several extra LED's of each color... some may break in this process, and they're not terribly expensive.

The LED mounting pieces came from Mouser Electronics. Representative part numbers are:

Red lens     593-3000R (other colors have a different last letter)
White spacer ring     593-SPC125
Black plastic retainer ring     593-RNG268

All these individual parts are very cheap. Get extras. The biggest expense is shipping. I should also note that it's not advisable to use a plain white LED behind these colored lenses. A plain white LED will tend to wash out the color of the lens a great deal. Better to match the LED color with the same lens color. All that having been said, as it turned out, the only place I needed blinkers was the oil pressure and stuck starter LED's, both RED.

There are several other, more out-of-the-box-robust assemblies available, including ones from SteinAir, RadioShack, etc. Unfortunately, the LED's with hard plastic cases from SteinAir sit quite high off the panel, definitely not flush, and have a limited viewing angle. Radio Shack has some nice plastic-encased LED's that are nearly flush, but they also have a narrow viewing angle. I wanted the co-pilot to have almost as good a view of these lights, especially the annunciator LED's above the left EFIS, as the pilot. That requirement led to the Fresnel lenses I used -- which also happened to lie very flush. The photo below shows a collection of the parts I used, and the RadioShack and SteinAir alternative styles. Of course, there are others too.

This picture shows, clockwise from top, 1) a "hobbyist" LED/resistor/wires assembly from SuperBrightLEDs.com, 2) another one where the resistor and red wire have snapped off the LED bulb, 3) red Fresnel mounting lens, 4) green Fresnel mounting lens, 5) black retaining rings, 6) white spacer rings, 7) one of the fully encased LED assemblies from Radio Shack, which does mount relatively flush, and 8) one of the fully encased LED assemblies from SteinAir. The latter two alternatives are mechanically robust, but suffer from a relatively narrow viewing angle, and the SteinAir model is not flush.

For more info, search on "LED" on the web site. Most of the relevant info will be on the first page of search results.

An updated electrical spreadsheet has been posted. New items, reflecting recent work, include quite a bit more on panel interconnects, updated details about flap controller & switch(s) installs, and various kinds of miscellaneous notes -- most about wire terminations, why and where they are.

Documentation for the FPS-Plus Reflex controller from Aircraft Extras.

While working on final switch hookups for the left side panel over the last couple of days, it's been essential, not mention convenient to record the details of the final switch hookups, focusing on the wiring and operation of things, while checking and re-checking. Perhaps the most complex switching accompanies the mult-modal, multi-layered electric flaperon system. Some new documentation has been added to the Design and POH sections of the Library to explain the wiring and operation of the system. These are works in progress, and will be improved from time to time. Although the notes added today are text, I'll be adding more and more to the documentation sections of the web site, including schematics of various kinds, as details are finalized "on the ground."

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