This is a very different project that aims at creating an Arduino based shield for battery-operated sprinkler. Although the work on creating an Arduino based controller for the sprinkler is in development stage, this one is ready to buy shield. The shield is designed to work with battery-operated sprinkler waves. The valves inside utilize a latching solenoid, which just draws power when you open or close the valve, and does not draw power in the event that it stays in the same state. Therefore, they are very efficient and are ideal for battery operated controllers.
Moreover, the shield can also be stacked with other shield such as WiFi to provide web control. There’s an on-boost converter which helps in generating high voltage require to open or close the valve. An H-Bridge has also been made by using 4 MOSFET switches to generate voltage in both polarities (Ex: -9V and 9V). Overall an exciting application of both analog as well as digital electronics. If you are interested in the shield you can buy it or even make it yourself with the help of manual available on the project website.
Frequency is very important parameter of any signal. No matter if you are generating or synthesizing signals, you most likely need to measure its frequency. When signal frequency is bellow 40kHz and amplitude is near 5V then you can build frequency counter on Arduino with standard LCD screen. If measure signal is 5V (or 3.3V) level then you can feed it directly in to Arduino input. In other cases you need to use limiting circuit like amplifier or voltage divider. But this small project assumes that voltage is fed directly to microcontroller input.
In this example signal comes to digital pin 12 where function pulseIn() counts number of pulses during specified time. Program itself is only few lines of code, and hardware is straight forward so putting it to work condition is only a matter of minutes.
There are many situations when you want to turn on the lights but switch is out of reach. Normally you could use some sort of remote control or even better – do this without additional hardware. This is where old good clap helps.
CsabaP have built an Arduino based clap activated LED strip. The original idea was taken from knock activated drawer lock where drawer opens when secret knock pattern is recognized. Building blocks are pretty simple including Adafruit Trinket, white light LED strip, microphone module, and other necessary parts. Setup is pretty simple, but it can be great help in many areas.
HDC1000 is small (8BGA) digital temperature/humidity sensor from TI which can be interfaced through I2C. Despite its small size, few newt features makes it really attractive. For instance sensor on package is located on the bottom so it’s not exposed to dust. Also there is a dedicated DRDYn pin which signals when new reading on chip is ready. This way you can build pretty effective applications where sensor itself can trigger MCU interrupt which could also wake it from sleep only when needed. Obviously for hobby projects 8BGA package may be little too small to work with. So for prototyping some sort of breakout board is needed. Francesco have built breadboard compatible breakout board which have necessary pins, I2C address selection and pull-up resistors ready to use it as compact building brick.
Sensor can be used with almost any microcontroller powered from 3,3V (sensor is also 5V tolerant). It can be successfully used with Raspberry Pi or Arduino. Arduino in this case is more attractive choice because there is a Library for it where with few lines of code you can get readings of both – temperature and humidity. Library is still in early development stage. It seems that so useful DRDYn isn’t yet supported. Also temperature and humidity readings are taken with different requests when it is possible to get all data at once. So hopefully library will be updated soon before adapter boards will reach larger audience.