Interfacing Circuits with Microcontrollers

Interfacing circuits with microcontrollers. In this article, I have discussed various elements and circuits interfacing with microcontrollers. These circuits are useful for those who want to work on embedded system projects but don’t have knowledge of electronics and embedded electronics. The following circuits will help you in the design of embedded system hardware circuits.

Transistor Interfacing Circuit

Figure below shows how to interface a transistor with a microcontroller. Diode D1 is used to avoid back EMF voltage in the case of an inductive load, such as a motor, as shown in the diagram below. In this circuit, transistor is used as a switch.

transistor interfacing with microcontroller
transistor interfacing with microcontroller

Relay Interface with Microcontroller

There are many applications where you need to interface a relay with a microcontroller, such as in high-power applications where you want to operate high-power loads like motors with the help of control signals from a microcontroller and power input from another power source. In such situations, we need a relay to separate the low-power control signals generating device from the high-power load, as shown in the figure below:

realy interfacing with microcontroller
relay interfacing with microcontroller

LED Interfacing with Microcontroller

I know, it is very easy to connect one LED with a microcontroller using a resistor, but one should be careful before connecting a current limiting resistor with an LED. Every microcontroller has a limit to sink and source current from its input/output pins. PIC microcontrollers can sink or source current up to 30mA. One should take care of current limits while selecting the resistor value. For example, if the current limit is 30mA and you want to calculate the resistor value, you can easily calculate it using Ohm’s law:

V = I * R;

We know maximum input and output voltage from microcontroller pin is about 5 volt and already know value of current i.e 30mA. So by using above relation

R = V / I = 5 / 30  mA = 167.76

So one can use standard resistor value of 200 ohm.

LED interfacing with microcontroller
LED interfacing with microcontroller

LCD Interfacing with Microcontroller

Diagram below shows a 16 * 2 LCD interfacing with a microcontroller. D0-D8 are data pins used to send data to the LCD. The rest of the pins are control pins used to perform various LCD commands like writing on the LCD, clearing the LCD screen, shifting the cursor to any position, and adjusting the text position on the LCD. A variable resistor is used to adjust the contrast/light of the LCD.

LCD interfacing with microcontontroller
LCD interfacing with microcontroller

L293D Motor Driver IC Interfacing with Microcontroller

L293D is a DC motor driver IC. It serves the purpose of an H-bridge up to 1 ampere. It is used for the direction control of DC motors, especially in university-level robotics. The interfacing circuit is shown below:

Motor driver IC L293D interfacing with microcontroller
Motor driver IC L293D interfacing with microcontroller

if you need any interfacing circuit , feel free to comment on this post.

5 thoughts on “Interfacing Circuits with Microcontrollers”

  1. Can you provide schematics for L293D Motor driver IC interfacing with microcontroller and with servo which is controlled by two push buttons left and right.
    Thank You sir

  2. can you provide schematics for L293D Motor driver IC interfacing with microcontroller and can you add servo motor which is control by push buttons left and right.
    Thank you sir


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