The other day my father and I were discussing about the problems of living in a third world country. Because of the social inequality, there is little security on the streets. Also one major problem is that no one is secure, even the 1% richer, because there are know cases of robbers getting inside homes even on private neighbourhoods. We ended up thinking about putting a home security system in our house. The problem is those are very expensive and, in general, they just ring an alarm to scare potential thieves, but they don’t actually warn you in real-time that your house is being invaded. A complete system would be even more expensive. So I got the idea to make my own Arduino based home alarm. I just had to buy a GSM shield for the Arduino Uno, because all other parts I already had.
Last post I started a discussion about some of the most common real-time clocks out there, and people gave some feedback to update the article. At the end, I chose the PCF8563 from NXP to use on the first smd version of my smartwatch (Arduino compatible). Of course all RTCs are fairly accurate, some more than the others, and as we’ve seen, from 2 to 20 ppm, but the real deal for this project was to use a module that consumes the least power possible, and on this IC is from 0.5uA (standby) to 200uA (I2C interface active).
Well, this is my very first post on this blog. First of all, let me introduce myself. I’m a Brazilian engineer graduated in mechatronics in a university called USP (or University of São Paulo). I don’t expect for you to know it, but for people that works in academics, it is a well known university, that was ranked 39º best of the world on the year 2009. However, English is not my primary language, because here we speak Portuguese. So expect some spelling mistakes.
On this first post, I’m going to describe some of the RTC modules available on the market, and how to use them. The advantages and disadvantages about each other and also their usage to make one of my projects, that is an arduino based smartwatch, with accelerometers, compass, altitude and pressure sensor. For this purpose, I had to search for the module with the least power consumption possible. For most of this I have to thank Dennis, another member on Instructable that helped me on my first steps with RTCs.