How to - Make a $25 Oscilloscope

I bought this $25 oscilloscope DSO 138 Kit online to use in electronics projects. Many electronics enthusiast
recommend getting a cheap oscilloscope for a first time user.

$25 Oscilloscope DIY Kit - DSO 138

This particular scope is both a kit that you can solder yourself and in the end a usable tool. Unfortunately, it only has 1 channel and the LCD screen is rather small. However for $25, shipping included, it was worth trying.

If you’re looking to buy your first DSO and don’t yet have that Dave Jones YouTube money, the DSO 138 might just be something to consider.

Adding Solder Paste / Placing SMD Components

I decided to buy the without the SMD components soldered on the board so that I can do some surface mount soldering. Once I got the package unpacked, I started to apply solder paste to the pads. Afterwards, I put some extra flux in areas where I thought it was needed. With the solder paste in place, it was time to place all of the surface mount resistors and the chips using tweezers.

Reflowing the SMD Parts

I started by slowly preheating the board with my hot air gun. Some of the resistors decided to fly about. In retrospect, I probably should have reflowed the board in an oven. With the board hot enough, I reflowed the components and adjusted accordingly.

Adjusting Pieces and Shorted Pins

Any component which tomb stoned or any pins that were shorted I corrected using my soldering iron. With the SMD part complete, I set about to prepare the through hole components. I soldered these in place and subsequently clipped the leads off.

Soldering LCD Headers and Verifying Voltages

After most components were soldered, I then completed the headers for the LCD screen and various larger connectors. It was now time to solder the headers to the LCD screen.

With the soldering complete, it was time to plug in the DSO 138 and verify that the build was successful by verifying the voltage at test pads on the board.

Cleaning the Solder Flux Residue

Once everything looked like it was working, it was time to give the board a good clean using isopropyl alcohol to remove any excess solder flux.

Veryfing the Functionality of the Oscilloscope

Finally, it was time to test the functionality. I quickly put together a PWM circuit using a 555 Timer and a potentiometer. The oscilloscope seems to work ok, it displays the PWM signal fine. I also tested the scope using the built in sine wave signal.