555 Monostable SMD Trainer Instructions

555 Monostable SMD Trainer Instructions

Table of Contents


What is the 555 Monostable SMD Trainer?

The 555 Monostable SMD Trainer kit is designed to test your skills at SMD soldering and provides you with a small circuit that blinks for a period of time once pushing the button. The length of time the LED remains on is determined by the value of the electrolytic capacitor and the setting of the potentiometer such that the smaller the size of the capacitor or resistance value of the potentiometer, the period will be smaller. To learn more about the 555 timer and how it works, you can check out the instructions for the 555 Monostable 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 555 Monostable SMD Trainer?

Besides the obvious use of improving your skills with soldering SMD parts, there are numerous uses for the kit. One potential use for the monostable is to act as a bolt lock mechanism for a door such that entering the correct code causes a bolt to briefly retract. If the door isn’t opened within a set time delay, the monostable re-engages the lock to prevent it from being left open.

Another use for the 555 Monostable is to control the spout of an automated drinks dispense. A small DC pump connected to a motor driver and 555 monostable can be configured to deliver exact amounts of fluid, and these can include water, juice, and fizzy drinks. 

Finally, the 555 monostable can also be used to control a power relay that enables a mains device to operate for a specific amount of time before automatically turning it off. For example, a games console can be connected to a monostable controller which prevents kids from playing for too long, and another example would be a sprinkler system that only remains on for a set period of time once activated.


Component List

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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 555 Monostable 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.

  • Integrated Circuits
  • Resistors
  • Capacitors (ceramic)
  • Capacitors (Electrolytic)
  • LEDs
  • Switches

Make sure that the LED, IC, and electrolytic capacitor are oriented correctly as they are polarised components. Inserting the LED in the wrong orientation will result in no light, and inserting the 555 IC the wrong way round will overheat and break. Components such as the resistors can be soldered in any orientation, and the potentiometer can only be inserted in one direction due to the use of 3 unevenly spaced feet.

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.