#Ds3231 use as timer how to#
#Ds3231 use as timer software#

To use an alarm function, attach an external pull up resistor tied to a voltage source not exceeding 5.5 volts. As an alarm, it is an active low, open drain output. The pin is multifunction and can be programmed to either output a square wave or as an alarm. Pin 3, called SQW/INT, is the alarm output. For bread boarding and prototyping it is convenient to use a carrier board which requires some fairly detailed soldering, but that is probably the most difficult part of the project construction. Apart from the DS3231M, the circuit has only a few other components and is a fully functional I2C RTC that can be used with many microcontrollers.įigure 1. The DS3231M used is packaged as an 8-pin surface mount device. Essentially, it is a simple break-out board that will allow connections to and from the RTC. Prototype basic DS3231M RTC circuit board.įigure 1 presents a schematic for the basic RTC circuit that can be used as the building block for a time-based switch.

The general concept, and the circuits presented, however, can be easily adapted for use with any microcontroller system using I2C communications.

#Ds3231 use as timer software#

The example presented also uses an Arduino UNO board with software written specifically to facilitate programming the alarms. The RTC also contains software trimming for specific temperature compensation and even an on-chip temperature sensor.

These include relatively high precision, I2C communications, an integrated resonator and easy battery backup. The DS3231M has a number of features that make it an attractive choice. Here, a DS3231M is used to construct a simple, but fully functional, RTC building block and, further, to construct an example RTC-based switch. Not all RTC chips have alarm functions but a few that do are the DS3231 (Maxim Integrated), MCP79410 (Microchip) and ISL12026 (Intersil). The advantage of this method is that power to a device can be applied at precise times, and only for as long as needed, which is desirable for battery operation. This project explores the use of these alarm functions to implement programmable, time-based, switches. While their major function is simple time and date keeping, some RTC chips also have programmable alarm functions.

The low-price, availability and relative accuracy of these chips, however, make them a desirable addition to many microcontroller projects. It is common to see these chips incorporated into computer motherboards or any appliance requiring access to the time. The approach can also be extended to a variety of external circuits to control battery power.Ī real time clock (RTC) is an electronic time keeping device commonly available as a single integrated circuit. Typically, these circuits include a power backup capability to retain the time while power is off to the main circuits.

#Ds3231 use as timer how to#

This project shows how to construct and program a DS3231M RTC as a power cycle switch. They can also be used to power external circuits for only as long as needed, making battery operation possible in many situations. Often overlooked, real time clock alarms can be used to switch power to external circuits at precise times. Use DS3231M RTC alarm functions to make programmable, time-based, switches to power devices on and off at precise times.