This is a simple project to teach soldering and electronics to kids (10+ years) and beginners. I first thought of a simple two transistor LED flasher, but then decided to make it interactive by adding a touch sensitive element to it. The idea is that once made, this PCB can be worn as a badge.

Step 1: Schematic

The touch plate consists of a few closely spaced copper tracks, and when you put a finger across a track, it acts as a resistor, sending a small current into the darlington pair Q1 + Q2, which amplifies the current and switches on the bistable multivibrator circuit formed by Q3 + Q4. The circuit is powered by a CR2032 coin cell.

Step 2: PCB

I’ve uploaded my gerbers to OSH Park. You can order PCBs from them using the link below.

https://oshpark.com/shared_projects/ETjUQUC9

Step 3: Components

You can find all design files for this project, including the Bill Of Materials (BOM) and gerbers, at my github link below:

https://github.com/electronut/blinky-badge

Step 4: Soldering

Soldering blinky badge is easy. Don't be intimidated by the surface mount (SMD) components. Actually once you get the hang of it, soldering these is quicker than through-hole components. Here is a fun cartoon guide to soldering with SMD components:

http://www.siliconfarmers.com/smtmanga/