Input Devices

Input Devices

By Saheen Palayi | 13 April 2021 | FAB Academy 2021

week 10 assignment is to measure something by adding a sensor to a microcontroller board that I have designed and then read it


we are just back after the easter break.I come late this week following a advice from the LAB instructor I decided to do this input Devices week and the upcoming output Devices week in a single design.So I planed to make a tiny tachometer my experience in electronics made it easier to design the final out put

Attiny Tachometer


A Tachometer is a device to measure RPM of a mechanical rotating part or device.It has a sensor input and a microcontrollers and a out put device like a Display then a power source to power the circuit


Input devices

Based on my knowledge and some research I made this block diagram.for this week I only exploring the sensor part rest will complete in upcoming output Devices week.

From the diagram u can see I planned to use a photo PhotoTransistor and an IR LED to detect obstacle that reflect the light and then I also using a OLED Display for showing the RPM

Photo Transistor

It's a electronics Active component more like a Transistor but instead of a base pin it has a face which detect Infrared light.We can control the collector-emitter current flow by adjusting the IR light Intensity that we given on the front face of the transistor


Input devices

The above picture shows the symbolic representation of an NPN type PhotoTransistor and also the component photo of THT and SMT types.This available on both NPN and PNP type but NPN is the commonly used one

Infrared Detection circuit

For the Tachometer I need to design a Infrared Detection Circuit which include an IR LED and a PhotoTransistor then couple of resistors

week 10 Group assignment is to probe an input device's analog levels and digital signals


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