Transistor Flasher SMD Trainer Instructions

Transistor Flasher SMD Trainer Instructions

Table of Contents


What is the Transistor Flasher SMD Trainer?

The Transistor Flasher SMD Trainer kit is designed to test your skills at SMD soldering and provides you with a small circuit that blinks two different LEDs. The frequency of the blink is determined by the value of the electrolytic capacitors and the charging resistors, meaning that the rate of blinking is fixed. To learn more about the transistor flasher and how it works, you can check out the instructions for the Transistor Flasher kit from MitchElectronics which also includes the internal circuit diagram of the 555 itself.

Use this kit to test out your soldering skills!

What can you do with the Transistor Flasher SMD Trainer?

Besides the obvious use of improving your skills with soldering SMD parts, there are numerous uses for the kit. One potential application is to use the flashing LED as a night locator that can be attached to the back of a bag. Simply put, these kits can be ideal for quickly locating others at night during hikes in a similar fashion to tail and wing lights on planes. 

On that note, the Transistor Flasher SMD Trainer can also be used on model RC planes that want to replicate the blinking lights used to locate craft at night. The SMD LEDs, albeit small, are brighter than you’d think, and can thus be used as a visual aid at a great distance during the night. 

The Transistor Flasher kit is also excellent for pulsing circuits that need to turn something on and off at regular intervals. One such example is a clock source for digital logic circuits that need a regular pulsing voltage (however, if using the transistor flasher with logic circuits, make sure the logic circuit operates at the same voltage as the transistor flasher otherwise you will likely damage the logic circuit).


Component List

TransisPCB ReferenceQuantityLooks Like
2N3904 BJT NPN TransistorQ1, Q22
680R ResistorR1, R42
5.6K ResistorR2, R32
100uF CapacitorC1, C22
3mm Red LEDD1, D22
PP3 ConnectorVDD, GND1


Construction Tips

3D Printable Jig

To help keep the board stable when soldering, you can download a free STL model of a basic jig that can be 3D printed with all common 3D printers. Watch out for the mounting hole pins as they may be vulnerable to snapping if using a low infill density, low wall thickness, or thick layer heights. Additionally, do not use hot air to solder the PCB when using the jig as you will melt the jig.

SMD Construction Guide

To learn more about how to solder SMD components, read through the MitchElectronics SMD Soldering Guide found in our resources section

Component Order

When soldering the Transistor Flasher kit, you will need to pay attention to the following chapters in the SMD soldering guide (which can be seen here). You should also solder the components in the order shown below.

  • Transistors
  • Resistors
  • Capacitors (Electrolytic)
  • LEDs

Make sure that the LED, transistors, and electrolytic capacitor are oriented correctly as they are polarised components. Inserting the LED in the wrong orientation will result in no light, and components such as the resistors can be soldered in any orientation.

Finally, ensure that you connect the battery connector correctly with the red wire connecting to the + terminal, and the black wire connecting to the – terminal.