Home automation isn’t about controlling a lamp with your smartphone. It is called “automation”. A home automation software should do things automatically. Do do this, it needs to have an idea what’s going on in your apartment (or outside). For this, you need sensors. While some sensor types are well-known you might not know what is available already on the market for a small budget. The following sensors can be integrated easily with your Arduino, EPS8266 or Raspberry Pi.
Almost everybody already did experiments with temperature sensors. The DS18B20 is a 1-Wire sensor that can be connected easily to many platforms. You will find a lot of code snippets for this sensor already. It has a 0.5 degree celsius accuracy which is more than enough for most use cases. If you only want to monitor the temperature, go for this one.
The DHT-11 and DHT-22 are two sensors that combine a temperature sensor with a humidity sensor. Both are more expensive than a simple temperature sensor. However, humidity informations might help you to do better automatisations. One use case could be turning on an air humidifier when the humidity is too low. Another would be opening windows, when humidity is too high. While these sensors also use a 1-Wire-type protocol, it is different from the 18B20 sensor. You can’t connect both sensors to the same GPIO. However as the DHT-11 has the temperature sensor already included, there is no need for an additional 18B20.
You’re plant are dying regularly because you forget to water them? Another use case for a sensor. Soil moisture sensors are available in 2 variants: the cheap sensors just measure the soil resistance. The problem with this sensor type is corrosion (over a longer lifetime). Capacitive sensors are becoming more popular and don’t show this problem as the electrodes are isolated. However, they are more expensive and a bit less sensitive. You need to experiment a bit to find the correct threshold for alarming.
You want to know if somebody is home? PIR motion sensors are also available for a few bucks and will give you information about people (or pets) moving. If somebody is just sitting or sleeping, the motion sensor won’t detect this. However, for many use cases this is just fine.
You’re not at home, but your teenage son. What do you think will happen? A party! Your neighbors will tell you tomorrow. Wouldn’t it be cool to automatically reduce the volume of your stereo system when the volume exceeds a specific level? This level might be higher at 5pm than at 11pm. A sound pressure sensor will do the job – at least until your son finds our where it is located and puts some damping onto it.
Small particles in the air can be a problem for some people – especially if you suffer from asthma. These emissions can come from various sources. Measuring the number of small particles in the air might give you an idea what might be the source and do something against it. These sensors are based on optical measurements. While this might sound complicated, sensors like this are not very expensive anymore.