One of the things that irks me during the design of the Playmates Toys MkVIII Tricorder or the actual replica, is that I cannot get uniform lighting on the four ALPHA, BETA, GAMMA & DELTA indicators. I can use SMD LEDs, push it deeper by a few milimeters and stick a diffuser in the front. The result would be almost uniform light but at the cost of its brightness. Since the turn of the Century, this has led me to always looking for that ‘perfect’ LED. My choices evolved from big (almost actual prop) through-hole LEDs to various variations of SMD ones. And each new chosen LED led to new board revisions, which explains why I have not finalised my design for close to three decades. And fyi, this is revision .
There are Four Lights!
Today, I would like to highlight the four rectangular openings of the ALPHA, BETA, GAMMA & DELTA indicators located at the left-hand side of the Tricorder screen. In the original prop, I surmised they must have used HP’s LED array or similar these were the only LEDs that can give uniform lights due to their diffused epoxy lens. They are quite rare now (and I only saw them around the 90’s) perhaps were only used as intended, which was as panel indicators.
Nowadays, it is hard to get them and even if so, the cost is far from ‘manufacturing’ price and they’re actually too big for the Playmates toy Tricorder. To overcome this issue, apart from searching for that elusive LEDs, there are two way which I can think of. But my main aim is to design the circuit board as thin as possible to allow for space for other electronics such as the sound player, the Lipo battery and its charger, and so on:
I can design to have four 0805 SMD green LEDs to sit flush within the Tricorder’s opening. As the plastic is thin, even if I secure it with a 0.8mm double-sided tape, I will still be able to see four bright mini dots or hotspots in a straight line. It can be quite obvious even if I put a diffuser between them and the sticker decal.
The other solution would be to pair the two 5x5x7 square LEDs together but because of their design, the PCB needs to be sunk 7mm into the Tricorder’s body. Again, when it lights up, there is a possibility you will detect two faint hotspots even if their lens are diffused.
(Image courtesy of gmleds.com)
The Phosphor Converted Green
More than a few years ago, I discovered a nice SMD LED called the 5730 (5.7mm long and 3.0mm wide). However, it was too bright (due to its water clear lens for non-white colours) and came with a very different shade of green. And in some cases, I need to use reflow soldering for better results since underneath the led, there is a middle solder pad for heat dissipation. All the more I discarded the idea. But just a few days ago, I discovered that there is new version of the 5730 LED called the Phosphor Converted version. Basically, there is a phosphor coating which converts the emitted blue LED light into another colour.
Summary
With every newly discovered LED, I was always drunk and full of excitement that this (current LED) would be the perfect solution to the Tricorder. I know I am a little fussy when it comes to lighting when a simple 0805 LED would do. There will come (multiple) a time where my mind would compare the lighting of that Tricorder with what I’ve seen on the screen. It might not be noticeable to others but dots of LEDs would make the Toy still look like… a toy.
Update 11.07.2025
Just about 20 minutes ago, during my Lunch hour, the LEDs landed on my Hands and I am so excited!
