DIY Oscilloscope: JYE Tech’s DSO 138

The first time I touched an oscilloscope was in college. I was taking a second semester physics course. And while the course labs made pretty heavy use of oscilloscopes, I, like many of my classmates, learned just enough about them to get by. I’d walk through each lab assignment twisting dials and pushing buttons until I got something on the screen that resembled what I was supposed to see. And that was about it. Any amount of understanding that I actually had fell out of my brain once the semester was over.

As a software professional, the first time I encountered an oscope was while working for a very popular (at the time) mapping software company. The company was developing a new edition of its handheld GPS device and the LCD panel they had been using was officially end-of-lifed. Our hardware folks were having a hard time picking a replacement. It came down to two panels – one from Sharp and one from Epson. I was tasked with implementing a software driver for the Sharp, while someone else got the Epson up and running. For two solid days, I sat in my cube next to an oscope that I really, really hoped I wouldn’t need to use. I spent most of my time banging around on SPI code and reading documentation. However, I’d occasionally hit a wall. That meant putting on my best sad puppy dog face and shuffling as pathetically as I could into one of the hardware guys’ offices to ask for some oscope help. In the end, I managed to get the driver working. But the experience wasn’t great and it bruised my ego somewhat. (As a bonus kick-in-the-fruitbasket, the company opted for the Epson panel.)

I really wish I could say that was an isolated incident. But the truth is that story has more or less repeated itself a few times throughout my career. The companies, colleagues, and products have changed, but the need to use an oscope continues to pop up.

A few months ago, I was watching an old episode of “Know How”. The episode was primarily about a cheap DIY entry-level oscilloscope kit from JYE Tech – the DSO 138. It looked super simple and a lot of fun to play with. There were no built in function generators and no fancy math functions. There were just a few buttons and switches to learn. It also appeared easy to assemble.

As I watched the episode, I relived each of my horrible oscope encounters. I felt slightly embarrassed to have come this far in my career without having some level of comfort with oscopes – even the DSO 138 intimidated me on some level. So I pulled the trigger and bought the kit.

About The DSO 138

As I mentioned above, the DSO 138 is an entry-level, DIY oscilloscope kit from JYE. Let me bold and italicize that phrase one more time – entry-level. It can only handle signals up to 200 KHz. It samples at a maximum rate of 1 million samples per second. And it’s limited to a maximum peak input voltage of 50 V. If your primary use case is audio applications or testing PWM signals, this kit should be just fine for you.

The kit arrives as a bare PCB board along with a 2.4” LCD, a bag of assorted components, test leads, and some assembly instructions. This being a kit, of course, means that you have to solder everything up. And depending on which flavor of the DSO 138 you get, you may or may not have to solder a few surface mount components as well. I’ll have more to say about this in a minute.

The scope is built around the STM32F103C8, which is an ARM-based microcontroller from ST. The STM32F103C8 has a 72MHz CPU, 2 12-bit ADCs (12-bits is the max resolution of the oscope, incidentally), 20KB of SRAM, and 64KB or 128KB of Flash (not sure which version was selected for this kit). It also comes pre-flashed with firmware for this project, so you don’t have to worry about doing it yourself.

The board features two options for power – a traditional barrel connector and a JST connector. There are 3 slide switches – one is for controlling in the input type and the other two are used to select range and sensitivity. Four buttons are used to control various on-screen parameters. A fifth button provides a reset. There’s also a USB connector included in the mix. It’s curious, however, because the USB connector doesn’t actually seem to have a purpose. It’s optional to install and the accompanying documentation says, “It was provided for future or user own use.” I haven’t been brave enough to see if I can power the board from it.

The board also features a built-in 1KHz 3.3V test signal, which you can use to verify that things are working as they should.

Purchasing the DSO 138

You can obtain the DSO 138 from a number of online retailers such as Amazon, Banggood, Ebay, etc. When purchasing the DSO 138, you should probably make sure you buy it from an approved seller. There are a number of counterfeit kits floating around. And JYE doesn’t mince words when it comes to them. They call out sellers by name both on their website and in their firmware splash screen. I purchased mine from an Amazon seller name NooElec, which is apparently on the “approved” list.

For reasons I describe below, I ended up buying two kits at two different times using the same Amazon link. And I got two different flavors of the DSO 138 – the 13803K and the 13804K. The only difference between these two versions are the surface mount components. The 13803K comes with all of the surface mount components presoldered. The 13804K has the ST chip presoldered and nothing else, which means you’ve got more soldering to do.

I thought I had bought the 13803K the first time, but the 13804K showed up on my doorstep. Unless the idea of soldering surface mount resistors strikes fear into your soul, it’s not that big of a deal. Incidentally, this was my first time with SMDs and I had no problem at all.

Something to keep in mind with this kit as well is that it doesn’t come with a case. If you intend to use the DSO 138 on a semiregular basis, you might want to consider purchasing a case. (This is especially true if you use leaded solder when putting it together. :-)) A company named Smartcoco makes cheap clear acrylic cases for the DSO 138 which can be found on Amazon. Unfortunately, it doesn’t come with instructions, so you’ll need to turn to YouTube for help


The DSO 138 assembly process is fairly straightforward. The directions are actually quite good. As in all electronics projects, you should always start out soldering the components with the lowest profiles and then work your way up to the taller, beefier components. It took me approximately three hours to finish soldering the main board (which includes a pee break and at least 2 soda refills).

If you do end up getting the 13804K and you’ve never soldered an SMD before, don’t panic. As I said before, I had never soldered SMD prior to this either. If my fat fingers and shaky hands can do it, so can yours. There are plenty of YouTube videos that provide tips and tricks for this. Just watch a couple of them prior to getting started and you’ll be just fine.

One minor annoyance about this project is that the through-hole resistors are blue (at least they were in my kit). The blue color totally messed with my ability to discern the colors of the resistor’s bands. I had to measure each resistor one by one to figure out what was what. There are only 23 resistors included, so it wasn’t terribly painful. And I suppose you should always measure these things anyway as a way of double-checking. “Measure twice, solder once,” as they say.

I did make the horrible mistake of doing some soldering while tired and feeling rushed. As a result, I soldered the pin connector to the wrong side of the LCD board. Whoops! This, of course, meant that I wasted a LOT of time trying to desolder it without destroying the solder pads or the pin connector…both of which I did anyway.

If, like me, you do screw up the LCD pin connector, you can find a replacement at AccuDIY. However, you’ll probably pay more than you should in getting it. The LCD is listed at $7.60 at the time of this writing. Shipping on that item was over $10 for me – way too steep for such a part. It actually made more sense for me to purchase an entire second DSO 138 kit in case I screwed something else up too (which I didn’t, thankfully. ;-)).

After I finished assembling everything, I did a quick test with the built in 1KHz 3.3 V test signal. That checked out ok. I then did a lengthier test using my favorite signal generator – my Sansa MP3 player. I fired up a Foo Fighters tune and watched the display dance around for a while.


I’ve still got some work to do in learning the DSO 138. When purchasing this kit, I also picked up a cheap high frequency signal generator kit. At the time of this writing, I haven’t assembled it yet. But once I do, I’ll probably write a short article about it as well.

What do I think about the DSO 138 thus far? It’s definitely worth the $25. Assembly was fun and gratifying. For low frequency signal sources, it seems to be fairly accurate. And the electrical noise level is surprisingly low. I definitely recommend it to everybody. Even electronics gurus will find one of these handy to keep in the toolbox (it’s portable!).

But as LeVar Burton says, “You don’t have to take my word for it”. Check out the DSO 138 review done by GreatScott!

Fatshark 600TVL Camera Holder for Diatone FPV250 V2

A couple of years ago, I built a 250mm quadcopter using a Diatone FPV250 V2 frame. This particular frame came with some sort of FPV camera holder that doesn’t actually seem to hold anything. So for a very long time, I resorted to zip-tying down my FatShark 600TVL camera. Inevitably, the camera would shift during flight. Sometimes the camera’s orientation would be weird but fine. Sometimes it wouldn’t be so great, often making it hard to even land.

I recently decided to do something about it. Using 3DSMax, I created three different frame-supported camera holders based on a design I found from a guy named Thomas Sevaldrud, which created a 600TVL holder for the ZMR250 frame. Kudos to Thomas for designing such a nice, and well-fitting, 600 TVL camera surround. I basically took his camera surround piece and added in custom frame mounts. All pieces were 3D printed using Shapeways’ “Strong and Flexible” plastic.

Design #1

At first glance, this design seems really nice. However, the tolerances on the gaps between the prop blades and the cage posts are pretty tight. It turns out that one of the props comes into contact with the camera holder. Not great if you actually want to fly the thing. Also, I realized that the camera is quite vulnerable in the event of a crash. The last thing I want is for my FPV system to be a casualty of my bad flying.

Back to the drawing board.

Design #2

This design works much better. The camera sits fully within the cage and the holder posts aren’t in any danger of being knicked by a prop blade. However, with design #2, my worry was that the camera holder was taking up valuable real estate inside the cage. I still have some tidying-up I’d like to do with my other components. So I wondered if I could do better, keeping the camera holder mounted using the front frame posts instead.

Design #3

This sort of blends designs #1 and #2. The camera sits back fully within the cage, and is still mounted using the front frame posts. In the design, I removed material from the frame mounts in the vicinity of the prop blades. It actually works pretty well. The only downside to this design is that I may have seated the camera holder a little TOO far back in the frame. Edges of the holder supports are slightly visible in the sides of the video feed. They don’t particularly get in the way, but they’re noticeable. I’ll fix this if I ever break it and need to reprint.


The latch is important as well. It’s what secures the camera in the holder and is used with all of the designs. (Again, big props to Thomas Sevaldrud for designing this).

The latch can be fastened to the camera holder using 2x8mm screws.


As for which design I like best between #2 and #3, I’m not entirely sure yet. It’s been too cold to fly with them. So time will tell.

If you’d like to try either of these designs out for yourself, here are the links to the STL files.

Design #2
Design #3

The inner diameter of the support posts is a bit tight and may need to be “opened up” a tad depending on your 3D printer settings. This was certainly the case with Shapeways prints. It’s not a big deal though. A 7/32″ drill bit used slowly will clean this up just fine.


Light Theremin

It was so hot and humid. It was also extremely crowded. There was barely enough room to turn around. And as usual, the idiots to the front and sides of me were either too high, too drunk, or too stupid to realize there wasn’t enough room to dance without stepping on or spilling beer all over the people next to them. I waited. And with my mind’s eye, I watched each bead of sweat travel from the nape of my neck and down my back. Did I mention it was hot?

It was August 1, 2003. Hundreds of us had packed into Bogart’s, a tiny little club in Cincinnati, OH, to see The Flaming Lips perform. We had endured hours of opening acts. When the Lips finally took the stage, the crowd tapped into its energy reserves. And it was amazing! What I had expected to be a plain ole rock show transformed into a carnival of blissful insanity complete with dancing animals, fake blood, giant balls, and an endless supply of confetti.

At some point during the show (I REALLY wish I could remember which song), Wayne Coyne began playing a theremin. Until that point, I had only ever seen theremins used for spooky, outer-spacey effects. A mood piece. I had never seen or heard one used to play an actual song, especially with a band. (Correction: Apparently that little whistle sound in the Beach Boys’ hit “Good Vibrations” is a theremin. I had no idea.) As Coyne’s arms and hands waved around in the air, producing sounds that crossed the line between melodic and psychotic, I was captivated.

I promised myself I’d try to play one someday. Unfortunately, this project is the closest I’ve gotten. 🙂

What The Heck Is A Theremin?


A traditional theremin looks like a box with one antenna popping out of the top and one out of the side. The thereminist (yes, that’s really what they’re called) moves their hands back and forth, away and towards the antennas. The proximity to one antenna controls the pitch of the sound that’s produced. The proximity to the other antenna controls the volume. The whole setup works by varying capacitance that controls a variable-pitch oscillator, which is really the source of all those crazy sounds.

Building a Cheap “Light Theremin”

A number of “light theremin” projects have appeared in my RSS feed over the past few years. And I had always intended to build one, but only recently did I actually get around to it. What follows is my take on the basic “light theremin”, as inspired by a version from Make Magazine.

Keep in mind that a “light theremin” is not a real theremin. Instead of varying capacitance, it varies the resistance of a photoresistor. And instead of an oscillator that produces pleasant sinusoidal sounds, it uses a 555 timer to generate square waves (PWM).

Below is the parts list and schematic if you’re interested. This project can be assembled in less than 30 minutes, if you’ve got the parts. And if you don’t have the parts, they can all be found on EBay for cheap.

Parts List

  • 1 555 Timer
  • 2 Photoresistors (Buy an assortment and try different ones)
  • 1 10 KOhm Resistor
  • 1 1 MOhm Resistor
  • 2 0.22uF Capacitors
  • 1 100uF Capacitor
  • 1 Speaker (Mine is a 30mm .5 Watt 8 Ohm speaker I found on EBay)
  • Optional: Assorted photodiodes
  • Optional: Potentiometer


The schematic calls for 6V DC. You can run it off of less. But as the voltage decreases, so does the volume.

Also, there are two photoresistors shown in the schematic. I had problems finding a photoresistor with a low enough resistance to use as an effective volume control. In the video below, I just used a potentiometer I had on hand. A photodiode might actually work better. At the time of this writing, I didn’t have any so I couldn’t try it.


If you have aspirations of building a performance instrument, you should probably look elsewhere. Light conditions vary from place to place. The response of this circuit can be unpredictable, even in the same room at different times of the day. Also, the audio produced is basically a square wave, which is the most obnoxious of all the basic oscillator types.

But if you’re looking for a fun project to do in an afternoon, this one is a lot of fun. Especially if you enjoy annoying everyone in your immediate vicinity. 🙂