Introduction: NOMAD From Original Star Trek Series With Light and Sound Effects

About: If you've got a problem, Yo, I'll solve it ! -Robert Matthew Van Winkle

If you are a fan of the original Star Trek series, you know what NOMAD is.
It appeared in episode #37 "The Changeling".

NOMAD is essentially a hybrid of an old earth space probe that collided with an alien space probe. The resulting hybrid probe gets its programming and mission corrupted in the process, and then goes on a genocidal quest to destroy "biological infestations" that it deems to be imperfect.

This has always been one of my favorite episodes of the original series. In many ways it is the quintessential classic Star Trek episode. If you have never watched the original series, and have to pick one episode to watch, I suggest this one.

Some highlights from this episode include:

FOUR red shirts get smoked!
McCoy gets to deliver his classic line "He's dead, Jim!"
Spock performs a mind meld.
Scotty gets killed, and then resuscitated.

NOMAD's lines are all great. Almost everything he says is a quotable classic. Here’s a few of his best:

"Non Sequiter. Your facts are uncoordinated."
"Insufficient response"
"I contain no parasitical beings."
"I am NOMAD. I am Perfect"
And the list goes on...

I thought it would be really cool to have a model of NOMAD. Ideally I'd like to have a super accurate full scale model, but I don't really have that much motivation. I primarily wanted a model that matched the overall appearance and proportions of the original prop. I started out intending to build a one half scale model, but after finding other sources of information it turned out my scale is more like 1:1.5.

This instructable covers the construction of the model and the sound and light effects.  Step 7 "Results" contains a link to a YouTube video of the model and the effects in operation.

There are actually very few others who have attempted to build a NOMAD replica, at least that’s what I could find through the first 10 pages of various Google searches. I have added a step at the end titled “Resources” containing links to the examples I found.

Step 1: General Construction

I made the model as a number of individual sections, which are later assembled into the complete model. Each of the sections has a hole through the center. This allows the upper and lower sections to be connected to the main body via a threaded rod or bolt that passes through each section stack.

I've numbered each section, starting at the bottom, as shown in the diagram. The second picture shows all the sections disassembled and primed before the final painting. Note the hole in the center of each piece used to connect the sections.

The steps which follow contain the general details of how each section was made. Some of the sections are fairly trivial, just simple cylinders or discs. Others took more effort, such as the truncated cone like sections and the main body box. The cone like sections were made on my 7 X 12 mini lathe. 

If you are not familiar with the mini lathe, I would highly recommend looking into it, if you are interested in that kind of thing.  An excellent place to get started is at .  This site have excellent tutorials, reviews, and how to guides for the mini lathe.

For the most part, the sections are made from pine lumber, plywood, or MDF. I used almost entirely scrap pieces I had on hand.  As you may well know, lumber that is referred to as 2 by, like a 2 by 4, is actually only 1.5 inches thick. Also, lumber referred to as 1 by is actually only 0.75 inches thick. If I refer to 2" or 1" lumber, I am implying the actual dimensions of 1.5” or 0.75”.

Step 2: Summary of Each Section and Its Construction

Section 1

This section consists of an octagonal box with a 1/2" thick plywood disk on top.
The octagonal portion is made from 2" pine lumber, with 1/2" plywood pieces for the top and bottom. The bottom of the box section can be removed to tighten the bolt that holds the lower sections to the main body. The picture shows this section with the bolt protruding from the top.

This section ended up having several differences from the original prop. If you look closely at screen shots from the episode and the more detailed plans at the link in the resources step, you will see that this is actually a 12 sided piece instead of an 8 sided piece. Also, the width of mine is a bit too small relative to the rest of the model.

Section 2

This section is a truncated cone shape. It was turned on a mini lathe. The piece was too thick to make from a single piece of stock lumber, so a 1.5" thick piece of pine was glued to a 0.75" thick piece of pine, to achieve the desired thickness. I used this approach of gluing together pieces of material to get the desired thickness on most of the other pieces that were turned on the lathe, as they were generally too large to be built from single piece of 1.5” material. This worked well, as I could build up the raw piece using standard thicknesses of material. If the overall length is too large, the excess can be easily removed with the lathe.

To create a piece of stock from other thinner stock in this manner, coat the entire area of one of surfaces of the pieces to be joined with wood glue, then clamp the pieces together over night. The result is very strong, with the glue bond being actually stronger than the wood itself.

Section 3

This is the 8 sided main body box. It was one of the more time consuming parts to build, but it is also straightforward.

Notice the 3 groups of small holes drilled in each side as shown. I actually drilled all of these with a drill press. In order to make the uniform pattern of holes, I first drew up each of the hole patterns, printed them out on paper, and taped the pattern to the plywood at the proper location. I then drilled through the paper at each spot on the pattern. These three distinctive groups of holes are present on all four of the larger sides of the body. Drilling all those holes on each of the four sides was tedious, but I was pleased with the result. I suppose that if you don't want to drill all those holes you could just make some kind of a decal of the hole pattern instead, but I wanted to have lights inside that would shine through the holes.

One side of the box is removable to access the inside, as is visible in the photo of the unassembled parts. Note the hole in the center, used to connect the pieces together with a bolt.

Section 4

The top of the main body box in the original prop has several small pieces on it. I did not attempt to recreate these details exactly, as I felt they were secondary in importance to the overall model. I did try to replicate the general appearance of these items, but I know that I omitted many fine details. One of the links in the resources step contains plans that are very detailed, if you want to go that far.

These small detail pieces were mounted on a sheet of 1/8” MDF. This whole assembly then mounts on top of the main body box.

Section 5

This section is just a cylinder, made from 2 thicknesses of 1/2" plywood.

Section 6

This section was probably the most challenging part. This is the large "head" section. I actually made this as three parts, and attached them together when complete. The diameter and length of this section as a whole exceeded the capabilities of my lathe, so I couldn't simply turn it on the lathe all as one large piece. Rather, I had to machine three separate pieces, and stack them up and glue them together after they were all complete. This was challenging because I had to make sure that the diameters matched up from piece to piece, without any visible discontinuities.

There are three “probes” or antennas on this section the original prop that NOMAD would extend and retract in the episode. My model does not have extendable probes. Instead, they are depicted in the retracted position. I created these details with finishing washers, 10-24 threaded studs, and 10-24 T-nuts. The studs have a wood screw thread on one end, and 10-24 thread on the other. They are threaded into the wood, and then the finishing washers are placed on the stud and finally the T nuts are threaded onto the posts. Refer to the pictures below for details.

Sections 7

This section is just two disks, made from ¼ “and ¾” plywood.

Section 8

This is another truncated cone type of section, made on the lathe from a single 1.5" thick piece of pine lumber with a disk of ½” plywood attached on top of that.

Section 9

This section is a set of 5 disks made from 1/8" thick MDF.

Section 10

This is another truncated cone type of section made on the lathe.

Section 11

The final section in the model is an antenna like piece on the very top. It is made from 3/16” and 1/8” dowels of different lengths. There is a small vane like piece on the very top of the center dowel, which I made from 1/8” MDF. The center dowel piece fits into a corresponding hole in the top of the section 10.

Step 3: Finishing and Painting

The grain on the wood pieces can be kind of coarse. Even after sanding, there are holes in the surface and visible grain. On the plywood pieces, the rough grain on the ends of the pieces cannot be really sanded smooth. To fill in these imperfections, I used wood putty. I just smeared it over the area as needed to fill any voids, and then sanded it smooth to the desired shape after it was dry.

After the sanding and puttying was to my satisfaction, I first primed all the pieces with brown rusty metal primer.

The final color of most of the pieces is grey. My paint mix doesn’t match the color of the original prop, but I thought it was close enough.

Some parts on the original prop are obviously made from metal. The main body looks to be made of aluminum sheet metal, and the section just below the antenna on the very top also appears to be made of metal. I used aluminum paint for both of these sections, and the result looks fairly good.

Step 4: Sound and Light Effects

I wanted the model to have some of the effects as shown in the episode.  The sound and light effects componenes are all housed in the main body box.  A block diagram of the effects system is shown below.

The sound effects are produced by recording dialog from the episode onto an MP3 player.  The audio is produced by playing back the recordings through an amplified speaker.

The light effects are generated using custom circuitry that I designed to drive arrays of LEDs that are visible through the holes in the side of the model as shown in the diagram below.

The following two sections cover the lighting and sound effects in more detail.

Step 5: Lighting Effects Details

If you watch the episode, there are two lighting effects in use. The upper two patterns of holes in the main body have red or red orange light shining out, which flickers on and off in sync with the voice. The lower square pattern of holes in the body has 5 individual green lights behind it which quickly flicker on and off in a seemingly random pattern. The 5 lights are arranged so that one is in each corner of the square and the last one is in the middle of the square, like the pattern of dots on the “5” side of a dice.  The light effects and their locations are shown in the diagram below.

For the voice sync effect, I created a PIC microprocessor circuit which samples an audio signal and sets a digital output high when the amplitude of the audio signal is greater than a threshold. This signal is then used to control the gates of FETs which in turn activate several strings of red and yellow LEDs. These LEDs are positioned such that they shine through the upper two hole patterns in the body. This effect is essentially the same as a “light organ”.

For the five random flashing green lights, I created a PIC microprocessor circuit that sets the five outputs either on and off as it continuously loops through a set of states stored in the program. Each of the five outputs on the processor control a FET that controls a string of LEDs corresponding to one of the five green lights on the model. The pattern of states generated was chosen randomly, to give the flickering effect like that seen in the episode.

Circuit Description

The function of the two effects circuits is as follows. Refer to the schematic.

J2 is the power supply input. A 12 volt battery pack consisting of 8 AA cells powers all the lighting effects.

The +5V supply is produced by voltage regulator VR1. D1 is a diode on the input to the regulator that prevents the circuit from being damaged if the power input is connected with the wrong polarity. Capacitors C4 and C5 filter the power supply input to the regulator. Capacitors C6 and C7 help stabilize the output of VR1.

U2 is the processor used to produce the green light sequencing. C3 is a decoupling capacitor on the VDD pin of U2. Q1-Q5 are FETs used to drive the five strings of green LEDs. R5 - R9 are current limiting resistor for each of the LED strings.

J1 is a 1/8" jack used for audio input. C1 capacitively couples the audio into the analog input of op amp U3.  R1 and R2 form a voltage divider which biases the input at ½ of VDD, so that the audio input signal swings above and below ½ VDD instead of above and below ground. This is needed because op amp is powered from the "single ended" supply (0 volts to 5 volts).  R20 and R19 set the gain of the amplifier. 

The equation for determining the AC gain of the op amp circuit is GAIN= (1 +  R20/R19).  So, with the values shown in the schematic for R20 and R19, the gain will be 6.  C7 casues the gain at DC and very low freqencies to be 1.  As a result, the output of the amplifier is the AC portion of the input multiplied by the AC gain, plus the DC offset established by R1 and R2.  For the values shown, the output will be the amplified signal riding above and below 2.5 volts.  C8 is a decoupling capacitor for the VDD pins of the op amp.

U1 is the processor used to produce the voice sync effects. The analog to digital converter input of the processor has an input range of 0 volts to VDD, so the output of the op amp is can be connected directly to it.  C2 is a decoupling capacitor on the VDD pin of U2. Q6 and Q7 are FETs used to drive the banks of red and yellow LED strings used for the voice sync effects. R10-R18 are current limiting resistor for each of the LED strings. R4 is a potentiometer used to set the audio input level at which the processor sets the output high. R3 is a pull down resistor that keeps the LEDs off while the output of the microprocessor is floating just after power up.

The two light effects circuits were built onto a single solderless breadboard. The LEDs themselves were assembled onto a perf board, with the LEDs arranged in groups to align with the hole patterns on the model. The breadboard with the microprocessors, FETs, and the rest of the circuitry is mounted on the back of the LED board. Refer to the pictures below to see the breadboard and LED board assemblies.

The completed breadboard and LED board assembly is shown in the pictures below.  This assembly is attached to one of the inside walls of the main body box.

Step 6: Light Effects Software Files and Overview

Two separate PIC 12F683 microprocessors generate the light effects, one for the flashing green lights, and the other for the red and yellow lights that flash in sync with the voice effects.

Both programs were written in assembly using Microchip’s MPASM tool that is free on their website.

The assembled *.hex file and *.asm source file for each program is included here, along with a high level flow chart showing how each program operates. The *.asm files also contain many comments throughout explaining the program operation.

The general operation of each program is as follows.

Flashing Green Lights

The program running on the processor that generates the flashing green light effects just retrieves the LED settings from a table of 20 different states. Each state is displayed for 300 milliseconds, and then the next state is looked up from the table and displayed, and so on. The program loops through the table forever, giving the appearance that the lights are flashing randomly.

Voice Sync Lights

The program running on the processor that generates the lights that flash in sync with the voice effects samples the audio using the processors internal A/D converter. From each sample, the magnitude of the audio waveform is determined, and it is compared against a threshold value. If the magnitude is greater than the threshold, the digital output is set high, otherwise it is set low.

The threshold is adjustable via the voltage on another input to the microprocessor. The A/D input is used to read the voltage on that input, and the result is used to determine the threshold. The program also incorporates some hysteresis to the magnitude comparison process.

This program also produces two additional outputs which are not used in the light effects on the model, but may be useful for other purposes. The first is simply a digital output which is the complement of the one used to drive the voice LEDs. This output is high when the other is low, and vice versa. This would be useful if an inverted output were necessary, so that the output was low when the audio signal was larger than the threshold.

The second unused output uses the processors PWM module to produce a PWM signal which has a duty cycle proportional to the magnitude of the audio signal.

Step 7: Sound Effects Details

For the sound effects, I used a really cheap Slick MP3 player. The user interface of the MP3 player is horrible, but the playback quality is more than good enough for the model.

The headphone output of the MP3 player is used to drive an amplified speaker for a PC.  Originally the amplified speaker setup had a left and right speaker.  I use only the left speaker, the other channel output of the amplifier is instead connected to the light effects circuit to control the lights that are synchronized to the voice.

The pictures below show the MP3 player and the amplified speaker.

I was able to find some audio files of NOMAD dialog on the web. I also captured some from the episode, and edited them as best I could. The files are loaded on the MP3 player.

Step 8: Results

Overall I am please with how the model turned out. 

However, if I had to do it all over again, here are a few things that I would have done differently:

The LED displays end up looking dim from the outside.  This is due to the fact that the main body is made of 1/2" plywood, so the LEDs on the board mounted inside are not very visible unless the model is viewed straight on.  This would be much less of a problem if the sides were made of, say, 1/16" sheet metal.

I wanted the video (link below) to show the light effects clearly, so I dimmed the room lights.  However, the video ends up a bit dark and grainy as a result.

The color is not as close of a match as it could be.  I just kind of eyeballed it, and it ended up being somewhat to light of a shade of grey.  Just a bit more black mixed in would make a difference.  I could go back and repaint it, but I have decided not to at this point.

Also, as I mentioned earlier, the bottome two sections are different in shape are proportion compared to the original.  This is one area where I would have benefitted greatly by doing more research up front.

Here is a link to a short YouTube video of my model playing showing it in operation, with light and sound effects.

Step 9: Resources

Arriving at suitable dimensions for the model was somewhat of a challenge. I started out trying to estimate dimensions myself from screen shots, and actually built some parts based on my own estimates. This turned out to be very difficult.

Later on I began searching the web for any others who had built a NOMAD model. I didn’t find many, but the ones I did find are listed below. Some of the information is much better than my initial estimates. Alas, I found most of this material only after I had started building. I did go back and modify some of my earlier pieces slightly, based on the newer information.


These plans are for a 1/6" scale paper model. With that model, you cut out the pieces from paper and fold them up and glue them together.
From what I can tell, the proportions in these plans look very good compared to screen shots from the episode. One mistake is that the very bottom section is 8 sided in the plans, but that piece on the actual prop was 12 sided.

These plans are from a guy who has put together some very detailed drawings for an extremely accurate full scale version. You can download his drawings in PDF format from his web site. This is the most accurate attempt I have seen.


I found a forum called the "Replica Prop Forum". This is a site for people who try to build copies of props from various movies and TV shows. The link goes to a thread with lots of pictures and comments on the work of another person who has undertaken construction of a very detailed replica.


This site is reporting a full scale kit that is available. It looks pretty good, but they want $300 for it.

I used the first two sources above for determining the final dimensions I used in my model, but I also modified them somewhat based on what I thought "looked right" compared to screen shots, and also based on the materials and equipment I have at my disposal.

I found a couple videos on You Tube of full size NOMAD models:

This video is of a scratch built model. The poster of the video claims that a 2011 issue of "Sci-Fi and Fantasy Modeler magazine"will contain a feature on how he made it .

This video is of a model that the poster claims is from a kit purchased on eBay.

These versions kind of put mine to shame, but I think that mine turned out okay for someone who isn’t a model builder as such.

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