Oscilloscope Project

I've found a use case for an oscilloscope. Dad has a nice, industrial scope from the 1960s, but being the size of a weekender suitcase, and weighing just as much, It was a little more than I care to have lying around the house. The next solution is the oscilloscope app for Android (of which there are quite a few). But when I found this one, I just couldn't resist. I picked it up from China (direct), and it only cost $21.00 plus shipping. Hard to beat that price, and to make things better, it's a kit, so I get to build it. This scope is a JYETech DS0138 scope.

Tools

I ended up using the following tools:

• Soldering iron (instructions call for a 20w. I used a 30w, and it worked just fine - I just took care not to linger, especially when working around the processors.
• Solder - good to have two sizes. I used one that was ~1mm in diameter, and the other ~2mm. The larger works really well for most components. The 1mm size was really useful on the USB and slider switch leads as they are really small, and close together.
• Multi-meter - I use a Fluke, but for this project, just about anything would work.
• Small Phillips screwdriver
• Wire cutters
• Small needle-nose pliers
• Solder remover (optional) - This should really be part of any project to aid in desoldering, if you make a mistake)

You will also need a 9v power supply (center positive), and for testing, something that can generate a signal (a cell phone with a tone generator app works really nicely), and a male-male 1/8" audio cable.

Building

Step one is taking stock of the contents (building kits is time consuming enough - no need to get knee deep into the build phase, only to find out there's a piece missing). Everything was there. There are two kits like this available from various Chinese resellers. The first is strictly the oscilloscope (board and LCD display). The second includes the Plexiglas case for $4 - $6 more (I opted to get the case, also).

One of the things to watch out for when inventorying components is that the resistors are VERY small, and they are all 5-band coded. This means it's very difficult to read the colors to validate the correct values. I ended up measuring them all with my multi-meter, rather than trying to read the color codes.

Next, we start soldering components. As a rule, secure resistors, diodes, jumpers and small capacitors first. These tend to sit lower on the board, and are more difficult to reach if there are larger components surrounding them. Next, hit the larger components on the inside of the board, and finally larger components and connectors on the edges of the board.

Once complete, you'll have a nearly finished board like this:

At this stage comes testing. This is really important. The instructions have you perform voltage tests before soldering over a set of jumpers. Important to follow the instructions so you don't damage the processors or display in the event something is not wired correctly.

Finishing

This was actually the hard part. You're provided 4 bolts with 8 standard hex bolts, and 4 rounded nuts (for the top). Use the 8 hex nuts to set the heights of the boards, and the 4 rounded nuts to secure everything together.

The case was shipped with three pieces of Plexiglas that were smaller than the two top/bottom pieces. You will need all three pieces. The one with the most holes goes under the display, and the display bolts on to it. The other two act as spacers (filling up the empty space between the display board and the top cover).

The time comes in making fine adjustments to the heights of each hex nut. If they are too low, you risk cracking the Plexiglas. If too high, the buttons will not stick out of the top. While yo are working on this part, take care, as the Plexiglas is rather brittle, and can crack easily.

Once you get the height set, you can start adding the Plexiglas layers. After the three inside layers are in place, drop in the red switch extensions (they must come before the top layer). Bolt on the top, and you're finished.

I added some labels to the finished product to make it easier to read.