Hi Low Detector SMD Instructions

Hi Low Detector SMD Instructions

Table of Contents


What is the Hi Low Detector SMD Trainer?

The Hi Low Detector SMD Trainer is a dual op-amp circuit that compares an input voltage to two different voltage levels; one representing too high and one representing too low. The two potentiometers represent the different high and low voltage levels, and the two on-board LEDs light up when either level is detected. The output of the Hi Low Detector is inverted, meaning that the Hi output switches low when the input is too high, and the low output switches low when the input is too low.

Use this kit to test out your soldering skills!

What can you do with the Hi Low Detector SMD Trainer?

Besides the obvious use of SMD training, the Hi Low Detector can be used in applications where a signal needs to be maintained at some level. For example, a greenhouse can use a temperature sensor to open windows if it gets too hot, but what about if it gets too cold? With the Hi Low Detector, the low output could be used to control a heater, thereby giving a greenhouse complete control over its temperature.

Another fantastic use of the Hi Low Detector is as a water tower controller. If the water level in a tank becomes too great, a safety valve can be controlled to drain some of the water. If the water level becomes too low, the same circuit can control a pump to refill water.


Component List

ComponentPCB ReferenceQuantityLooks Like
0805 100R ResistorR11
0805 1K ResistorR2, R32
0805 10K ResistorR4, R5, R6, R74
0805 100nF CapacitorC11
100K PotentiometerRV1, RV22
0805 Red LEDD2, D32
1N5817 DiodeD11
Red WireVCC1
Green WireVIN1
Blue WireOUT2
Black WireGND2


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 Hi Low Detector, you must 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
  • Transistors
  • Resistors
  • Capacitors (ceramic)
  • LEDs
  • Diodes
  • Potentiometers
  • Wires