TR-595E: 001 CIRCUIT ANALYSIS

FUSION360. YAY OR NAY?

Arky (aka Nicholas Doucette) has uploaded all his files into his Github account. His TR-595E was created mostly from AutoDesk’s Fusion360. I am amazed at the Fusion360 suite of tools. But the monthly subscription is a stopper. At my Country’s weak currency, I would be paying 4.4 times.

Fusion360’s capabilities lies in the 3D modelling and EDA (Electronic Design Automation) and, I suppose, integrate them seamlessly for the purpose of manufacturing. It is good to have, but I do have my own solutions which I am comfortable with. I use EaglePCB for my Circuit and PCB design, InkScape for my Artwork and well, Photofiltre for this Website. I only need to learn up Blender (not just SketchUp) to start my journey into 3D.

THE 555/4017 CIRCUIT

Ever since I set my eyes on the MkVII Tricorder in Star Trek the Next Generation, I was, and still is, attracted to their blinking and sequencing lights. Years later, through books and Internet (although still in its infancy), I guessed that most if not all, circuits were based on the 555/4017 pair as there was a distinct pattern. If you Google it, there would be a lot of that circuit nowadays. You can use it to create simple running lights, a K.I.T.T. or Cylon scanner and control other stuff.

Here is a good animated example from www.iamtechnical.com which I hope would be able to let you understand how fantastic this simple circuit is. Here, the Author has configured the circuit to behave almost like the front sensor array of the Tricorder.

Basically, the 4017 IC (also, please observe anti-static precautions) is a CMOS Decade Counter. It uses clock pulses to count the LEDs from 1 to 10. Depending on the shape of the clock pulse, the duration of the LED switched ON will also change. So, the 555 Timer IC is the most suitable chip to do that unless you want to use a single microcontroller, which can replace the whole circuit. There are more Clock Pulse generator circuits such as the RC (Resistor/Capacitor) circuit, simple flip-flops using transistors and even (more interestingly), pulses from other circuits which gives a weird timing sequence.

Anyway, for the first step into this Project, let’s explore the files from Mr. Duchette’s Github Repository. Usually, there are three PCBs in any TNG, DS9 and Voyager Tricorders which are mainly responsible for lighting LEDs and their sequencing.

By logic, you will know a device is doing its job when there are flashing indicators and animated screens. The more it has, the ‘busier’ it is. And so, using this argument, the Mk IX/X and the Engame Tricorders are the ‘busiest’ Tricorders.

TOP PANEL PCB

The TR-595E’s top panel, if we were to follow the design logic of the MK VII, IX and X, shows the Tricorder’s power status, its activity and so on. And on the right panel, it would have a animated 4-LED sequence, sweeping from left to right. The TR-595E has a rather nice looking yellow bar instead. There is a reasoning to this since the moving 4 LED might distract the user from the wonderful animated LCD screen.

THE ORIGIN OF THE TR-595E? (FUN SPECULATION)

OK, let’s take a break.

Just like the ‘Blood Oath’ Episode Tricorder, it is the very first Tricorder with an actual working LCD screen. Due to the technology at that time, the LCD screen was quite bulky and so, the rest of the lights where possible, are just electronics. In theory, this is a variant of the TR-580 and you can say that the TR-595E is a branched off evolution from it.

Take a look at the image below. Notice that apart from the big LCD screen, all the Tricorder controls, especially my favourite ALPHA, BETA, GAMMA & DELTA are gone and only the lower flap are still ‘functional’.

https://twitter.com/i/status/1265810808782696454

THE OFFSPRING OF TR-580 and OSX?

So this got me thinking. What if the TR-595 was from the same designer even though both models are 20 years apart and from different timelines? Let’s say, you combine the TR-580 variant’s Big Screen with some lower interface controls off the OSX, and put them into the Mk IX body. Would that be the TR-595E? Ha ha ha ha.

I love the TR-595E, especially its Lower Interface flap where the 4-function LEDs has been relocated. It is a long shot but I am still hoping there is space at the bottom of the LCD to fit the GEO, MET & BIO buttons. Then it would confirm the theory! Ha ha ha ha!

LOWER INTERFACE PCB

The TR-595E’s Lower Interface are the Tricorder’s controls and although it has the, um, allegedly 4-LED ALPHA, BETA, GAMMA & DELTA animation, it is not described in the decals. (So, yeah, I would have to modify the decals)

This section is powered from the same 3.7v Lipo battery located in the main body. The pair of metal hinges serves as the ‘wiring’. If there was a third metal hinge, command can pass through from the Lower Interface and changes the animation on the LCD.

You can shape the square wave of the 555 timer by changing the values of R1, R2 and C1. Long ago, there was a software written by one Mr. Andy Clarkson (http://555-timer.clarkson-uk.com) but his Website is down and he has lost the original source code for this software. So, if you really want to download and run the software, you would most probably need a Win95 PC.

THE SINGLE CURRENT LIMITING RESISTOR

Coming back to the circuit, take a look at the current limiting resistor R3. By normal convention, you will need one current limiting resistor for each LED but here, R3 is doing most of the work. Mr. Ducette is very innovative here because since only one LED comes on at a time, the resistor is able to support this. In all datasheets and circuits, this is the first time I have seen this theory in action. Don’t worry as the resistor will not get warm as the current is very low, about 10mA per LED. Not only is this brilliant, he has save three resistors and in terms of production cost, that would be some savings.

CURRENT LIMITING RESISTOR CALCULATION

This is how I got the 10mA for the green LED, here is my calculation below. I usually use this to calculate the value of the current limiting resistor per LED but for here, it is used to calculate the current instead. So, I swapped R3 with LED Current to get the answer.

I was wrong to assume that all the LEDs in his Tricorder are running at 20mA each. The 150 Ohm resistor values was a red herring for me.

So, in summary, all the electronics within the TR-595E are powered from a single 3.7v LiPo battery and the LEDs are running at 10mA. There was no need to use 5 volts.

FRONT ARRAY PCB

This is the most exciting part of the Tricorder (according to… me). This is the front sensor array which, if you were using a Tricorder, a Star Trek Offic.. er, Fan, would know. With so much LEDs in there, it would be very difficult to ignore.

The front array design from the Mk IX/X uses TWO scanning arrays. You still have the normal MkVII green array but the additional array is located at the bottom. And so, the following image is the circuit for that.

There are two 555/4017 circuits, running on different slightly different speeds. The two circuits are identical except for the capacitors connected to the bottom of the 555 ICs. Capacitor C1 uses 4.7uF while C3 has a value of 2.2uF. Notice how Mr. Duchette uses single resistors for all the 4017 outputs, D17 and D18 LEDs. So, you only have to solder 15 SMD resistors instead of 29. This is a revelation to me.

I have ordered the Front Array PCB after downloading from Mr. Doucette’s Github Repository. His Gerber Files for the PCB are ready to work with JLCPCB.com. And they are so beautiful!