Credit Card Sized PCB Stylophone

In this Instructable, I will show you how to build a credit card-sized PCB Stylophone.

For those who don't know, the Stylophone is a miniature analog synthesizer that you play using a stylus. It was invented by Brian Jarvis back in 1967. This project puts that classic instrument right in your pocket!

1. PCB
2. LMC555 - 1
3. PAM8302 - 1
4. TP4057 - 1
5. MMBT3904 -1
6. SMD Led 0805 yellow - 1
7. SMD Led 0805 Green - 1
8. Ferrite bead - 2 (Link to buy)
9. TYPE-C 16PIN USB Female port - 1
10. On/Off slide switch (SS-12D07G4) - 2 (Link to buy)
11. Alligator clips - 2 (Link to buy)
12. Silicon wire 22AWG - (Link to buy)
13. M2 8mm screw - 4 (Link to buy)
14. speaker - 1 (Link to buy)
15. 3.7v 300mah Lipo battery - 1 (Link to buy)
16. 3D printed case

All SMD capacitors and resistors are 0805 size

Capacitors

1. 10uf 16v tantalum - 1
2. 33nf - 1
3. 220pf - 2
4. 1uf - 2
5. 100nf - 5
6. 10uf - 3

Resistors

1. 100R - 2
2. 560R - 1
3. 1k - 2
4. 1.5k - 2
5. 1.6k - 1
6. 1.8k - 2
7. 2k - 1
8. 2.2k - 2
9. 2.4k - 2
10. 2.7k - 2
11. 3k - 2
12. 3.3k - 2
13. 3.6k - 1
14. 3.9k - 2
15. 4.3k - 2
16. 4.7k - 2
17. 5.1k - 2
18. 10k - 2
19. 24k - 1
20. 68k - 3
21. 10M - 1
22. 4.7k SMD Pot - 1 (Link to buy)
23. 10k SMD Pot - 1 (Link to buy)

For this project, I used the Stylophone circuit by drj113 as the main reference. You can check out his amazing Instructables for a deeper understanding of how the original circuit works.

My version is slightly different. I added a vibrato function (vibrato creates a wobbly effect), used a different amplifier, and also added a small battery charging circuit. The main oscillator section is still based on the design of drj113.

I built this project using components I already had on hand, so there is definitely room for improvement.

I used small SMD (surface-mount) potentiometers for tune and volume, which require a tiny screwdriver to adjust. For an easier-to-use version, I recommend using side-mounted dial (thumbwheel) potentiometers instead. Similarly, side-mounted switches might be better.

I designed the PCB using EasyEDA. I will share the project link, so you can copy it and tweak it based on your own component availability and preferences.

https://oshwlab.com/electronics220903/pcb-stylophone

The front of the PCB looked a bit empty after I placed all the components. To give it a unique style, I added some fun doodle art to the empty spots. This is totally optional, but I think it makes the final project look cool!

After designing the PCB, the next step is to get the board manufactured. You can use any PCB manufacturer you prefer for this project. For my build, I used Lion Circuits. They were kind enough to sponsor the PCB fabrication for this project, which helped bring this Stylophone idea to life.

I selected a Black solder mask with ENIG finish. ENIG not only looks premium and clean, but it also provides better conductivity for the stylus contact pads.

Lion Circuits also sent me few White solder mask PCB versions as well, which look pretty cool too.

After inspecting the PCBs, I started soldering all the components. In my build, I soldered everything by hand, but you can also do reflow soldering if you have the tools. Many PCB manufacturers also offer assembly service, which can save a lot of time if you don’t want to solder SMD parts yourself. (Check out Lion circuit's assembly service)

When hand soldering, make sure to pay close attention to component polarity:

Tantalum capacitors have a line marking the Positive (+) side.

SMD LEDs usually have a small green mark which indicates the Negative (-) side.

After completing the soldering, clean off the flux residue using IPA (Isopropyl Alcohol).

Next, I soldered two wires to the speaker and then connected the speaker to the PCB. The speaker I used is a simple toy-grade speaker 16ohm 0.25w, so the sound quality is not very high. You can upgrade to a better speaker if you want a cleaner sound output.

After that, I soldered the battery wires. Be extra careful during this step. Battery wires are very close to each other and can cause a short circuit if the solder joints touch.

For the stylus, I used two alligator clips. First, remove the plastic sleeves from the clips and solder a silicone wire (around 20 cm long 22AWG) to them. After soldering, slide the sleeves back on.

I chose silicone wire because it is much more flexible compared to normal PVC wire, which makes it easier and more comfortable to play the Stylophone.

Then I did a quick test to make sure everything was working properly. During testing, I noticed that I had made a small mistake — the vibrato switch was inverted. I corrected this issue later in the EasyEDA design file. Then I proceed with designing a simple case, because the exposed battery doesn't feel safe.

Next, I opened Tinkercad and designed a simple case for the Stylophone. And 3d printed it.

Next, I glued the battery and the speaker onto the PCB. I used CP-0001 glue for this. After that, I placed the PCB inside the 3D printed case and secured it using 4x M2 screws.

And that’s it! Our Stylophone build is complete and ready to play.

Before using it, I fully charged the battery. There are two indicator LEDs on the board — Yellow for charging and Green for fully charged. One thing I noticed later is that the LEDs are on the bottom side of the PCB. It would be more convenient if they were placed on the top side.

Now for the fun part! I’ll admit it, I’m a total beginner when it comes to music. I thought this would be easy, but it’s really not! This project gave me a whole new appreciation for musicians… it takes real skill.

Even so, it feels incredibly rewarding to play music on an instrument you built yourself from scratch. I did manage to play a few basic riffs in the end, even if they sounded a little questionable!