Arduino scratchpad - just some rough notes and observations.
1) Real time clocks and the arduino.
I've been tinkering with the Arduino since the autumn of 2013 and have tried out various peripherals - temperature, humidity and light level modules etc. - all good fun.
The only one I've had trouble with is the DS1307 RTC (Real time clock). The first one I bought drifted by about 2 secs an hour, an annoying error when one is used to high accuracy from even the cheapest digital watches. I bought a second unit (they're not expensive) and even tried fitting another clock crystal from Maplins but the inaccuracy was still there.
I then tried a DS3234 module and finally got the accuracy I was after. These are a superior module with temperature compensation. The first unit has been working in a unheated outhouse during a British winter controlling some outside lighting and has kept very accurate time. I now buy very cheap ones from ebay based on the DS3231 a sister chip that (I think) just lacks the alarm capability of the DS3234 but seems highly accurate too.
2) Arduino Nano and Multi Expansion Board Shield.
I've been using the Arduino for a few months now, trying out the UNO, Mega, Nano and Pro-Mini. I do my prototyping on a UNO and move them when completed to a combination of the Nano and the Multi Expansion Board Shield.
There are two advantages to this:- cost and convenience. The cost of a Nano is around £x.xx and that of the shield about £x.xx on ebay.co.uk. The convenience comes from the pinouts on the shield. On a recent lighting project I could connect up three I2C devices to the shield ( a 2004LCD display, a DS2131 real time clock module and a BH1750 digital light sensor ) with ease.
The usual cop-out : -
Apologies for any mistakes, but whilst I'll take every care to keep things accurate, I cannot take responsibility for any errors.