Programmable relay switch using PIC MCU (revised version)

Programmable relays are key elements in numerous automation applications such as automatic street light control, watering and pump control, HVAC, home automation, power plants automation in industries, etc. This article describes a DIY programmable relay switch using PIC16F1847 (PIC16F628A can also be used) microcontroller. It is a revised version of my previous PIC-based relay timer project with added features and some improvements in the circuit design part. Like my previous version, it also allows you to set both ON and OFF times. The maximum time interval that you can set for ON and OFF operations is 99 hours and 59 minutes. The new version features cyclic option, which means you can choose to run it in a continuous loop of ON and OFF cycles. The timer can be programmed through 4 push switches. The programming menu, relay status (ON or OFF), and number of cycles completed are displayed on a 16×2 character LCD. The timing resolution of this relay timer is 1 minute. The timer also saves the previously-set ON/OFF times and the cyclic option in its internal EEPROM so that it can retain these values after any power supply interrupt. The firmware for this project is provided for both PIC16F1847 and PIC16F628A microcontrollers.


Programmable relay timer switch

Here are the summary of the features that this programmable relay switch has:

  • On-board +5V voltage regulator (operates at 9-15V DC input)
  • OFF and ON time setup for the relay operation
  • Option for cyclic run (maximum 100 cycles, after which the timer stops automatically)
  • Stores ON/OFF times and Cyclic option from previous setup into internal EEPROM
  • ON/OFF timing range: 0 to 99 hours and 59 minutes with 1 min resolution
  • Interactive user interface using 4 tact switches and a character LCD
  • On-board buzzer alarm
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The World of TI’s Tiva C MCUs

Most of us who work with electronics know the name of Texas Instruments (TI) as a manufacturer of several important digital and analogue ICs as well as fancy sophisticated scientific calculators. However many people don’t know that TI is also a manufacturer of some of industry’s best microcontrollers. TI’s portfolio of micros is pretty large. ARM micros are getting popular day-by-day and on that family of micros TI has some of the best devices one can imagine. One such family from TI is the Tiva C series. Enter the TM4C123x Tiva C micros – one of the best possible combination of high-end hardware ever integrated with an ARM Cortex M4.


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This DIY bicycle GPS can convert any bike into smart bike by adding navigation support. This bike GPS connects to the user’s smartphone GPS via Bluetooth and receives the navigation data from a GPS application on the smartphone. The project uses an Arduino board and a Neopixel LED ring. The destination is set on the GPS application on the smartphone and the directions are shown on the LEDs.

DIY GPS bike

DIY GPS bike

In this project, we will use a GPS application available on Android or IPhone, OsmAnd, a mapping application and navigation with access to free data OpenStreetMap. This application is available offline, that is to say that one can use this application without using the cellular data (3G or 4G).

We use an Arduino micro type microcontroller as it is quite simple to use and is inexpensive. It is connected with a Bluetooth headset.

This headset is the link between the Arduino board and telephone. To indicate the direction to the user, we use a ring of 24 LEDs connected to the Arduino board. These are Neopixel LEDs, they are the most efficient LEDs. We can control the color and light intensity of the LEDs.

Microchip Announces a new Graphical User Interface Composer Tool

Microchip announces MPLAB Harmony Graphics Composer, a free development tool for engineers to easily develop and design professional graphical user interfaces.
Microchip Technology Inc. (NASDAQ: MCHP), a leading provider of microcontroller, mixed-signal, analog and Flash-IP solutions, today announced the MPLAB® Harmony Graphics Composer (MHGC), a modern and flexible graphical user interface (GUI) composer tool. MHGC is a free development tool for developing GUIs for all PIC32 microcontrollers through Microchip’s Harmony Configurator and MPLAB X Integrated Development Environment (IDE). The software allows anyone to create branded content using the Harmony Graphics Library, in conjunction with their custom assets, to create GUIs in a What-You-See-is-What-You-Get (WYSIWYG) design model, without complex and cumbersome coding.
MPLAB® Harmony Graphics Composer (MHGC)

MPLAB® Harmony Graphics Composer (MHGC)

Si4844 and Arduino make a full-featured AM/FM/SW radio

Raymond Genovese from All About Circuits has shared his idea of making a full-featured AM/FM/SW radio using SiLab’s Si4844-A10 radio chip, which is the first analog-tuned digital-display digital CMOS AM/FM/SW radio receiver IC integrating the complete receiver function from antenna input to audio output. It works with Host MCU through I2C-compatible 2-wire control interface.


AM/FM/SW radio using Si4844 chip

The idea of a single chip radio is intriguing. The prospect is especially interesting to me because, frankly, I envy the analog skills I associate with building a radio receiver. When I browsed the circuit literature in the area, I came across the Silicon Labs collection. One of their chips, the Si4844-A10 caught my attention. This receiver has AM/FM/SW capability with all the bells and whistles and it is designed to work with a microprocessor. Best of all, the support components required are mainly associated with the microprocessor display and control functions with only a small amount of antenna support needed. I couldn’t resist taking the plunge.

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