As an introduction, mini project is a part of syllabus in ELE 526 where need cooperation among members in a group to think for how to solve about the tittles given. Our group has been given tittles of “SCHMITT TRIGGER SWITCH”. In reality, Schmitt trigger is used when interfacing an analogue signal to digital signal. One of its functions is to detect level of sensed. When the input signal reached to a given level, it will switch from its low state to high state. Transistor is a component used as a transistor switch and able to control high power devices such as lamp, motors and digital electronic device. Two types of transistor are NPN and PNP which both of them are different on how the current flow. For an ideal transistor switch, between collector and emitter current resulting too zero means off state and on state while the resistance reach zero and have maximum current flow.

In this project, it is required for the schmitt trigger circuit detect an input signal between ranges of 4V to 8V.After an input signal have been detected, that value also can be used to control light emitting diode (LED) through a switch. Switch in this circuit have been replace by a NPN transistor. Then, this transistor was ON the light emitting diode (LEDs) as the value detected decrease to 4V and OFF the LEDs when increase to 8V.




  The circuit consist different type of component use to make sure the LED will light up when the input voltage is 4 V. Led will turn off when the input voltage reach 8V. The component use in this circuit is:

  1. power source

  2. resistor (15.4k,10k,6.8k)

  3. op-amp UA741

  4. transistor

  5. relay

  6. light emitting diode (LED)

  Inverting op-amp is use in this circuit because the input voltage (Vin) is connected at negative terminal op-amp. The op-amp is connected by using Schmitt trigger. Schmitt...