Tag Archives: PIC12F683

Add a reminder to your washer

Most washers don’t have a built-in reminder. Mine doesn’t have either and a lot of time I have forgot my clothes inside it after they are done. The wet clothes smell really bad if they are left inside the washer for a while. If you have a similar issue with your washer, you might want to build this project which adds an audible reminder to the washer that will beep when the clothes are done.

Reminder for washer

This project is based on an accelerometer that continuously senses the vibration of the washer when it is running. When the clothes are done, the washer stops and so does its vibration. The PIC12F683 microcontroller turns on an alarm when the accelerometer doesn’t get any movement for a preset time interval.

Temperature and relative humidity display with adaptive brightness control

The objective of this project is to illustrate a technique of implementing adaptive brightness control to seven segment LED displays. It consists of a closed loop system that continuously assesses ambient light condition using an inexpensive light-dependent resistor (LDR) and uses that information to adjust the brightness of the display. For the proof of concept, the technique is applied to construct a digital temperature and relative humidity meter that adapts the brightness of the seven segment LED displays to the surrounding lighting conditions. There are 8 seven segment LED displays used in this project and they are all driven by one MAX7219 chip. The ambient temperature and relative humidity are measured using the DHT11 sensor. The microcontroller used in this project is PIC12F683, which is a low-pin-count (8) device from 8-bit PIC microcontroller family. Auto-adjusting the brightness of the seven-segment LED display with surrounding illumination enhances the readability in all ambient lighting conditions.

Temperature and humidity display with auto-brightness control

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Digital logic probe for troubleshooting TTL and CMOS circuits

A logic probe is considered as a stethoscope for engineers and technicians for debugging digital logic circuits that consists of logic gates, memories, registers, etc. A digital multimeter (DVM) can also be used for such analytical purposes but it gives you the numeric value of the voltage at a point instead of the logic state. Depending on whether the circuit is based on TTL or CMOS components, the voltage levels for logic 0 and 1 could be different for each family. DVM users, thus, have to calculate logic levels from the measured voltages, which consumes time and delays the troubleshooting procedure. A logic probe, on the other hand, does all these functions automatically and shows meaningful logic states at test points. In this project, we will discuss about making a digital logic probe that is applicable to both TTL and CMOS circuits and uses minimal components.

Logic probe for CMOS and TTL circuits

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Connecting multiple tact switches on a single input pin of a microcontroller

Normally one tact switch requires one digital input pin of a microcontroller. Some designs implement keypad style multiplexing to get multiple switches on fewer inputs. However, there exist other techniques that allow you to connect many switches on a single input pin of a microcontroller. This tutorial demonstrates one such technique as applied to PIC12F683 microcontroller. In this example, there are four LEDs and four tact switches connected to the PIC12F683 microcontroller. While each LED is controlled through an individual I/O pin, the four switches are connected to one ADC input pin of the PIC12F683 microcontroller.

Connecting multiple tact switches to one input pin of PIC micro

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Expanding the number of I/O lines using Microchip MCP23008

A microcontroller comes with a limited number of general purpose input and output (GPIO) ports. However, some applications may require more ports than are available on the microcontroller. In such a case, GPIO expanders can be used to increase the I/O capability of the microcontroller. MCP23008 is one such device (manufactured by Microchip Technology) which provides an easy I/O expansion using 2-wire serial interface. This tutorial illustrates how to add an extra 8-bit I/O port to PIC12683 microcontroller (which has only 6 I/O pins) using MCP23008. A seven segment LED display and a tact switch will be connected to the extended port. The PIC12F683 microcontroller will count the switch presses and display the counter value on the seven segment LED  module.

MCP23008 port expander interfaced to PIC12F683

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