Have you ever want to DIY an Aquarium controllers to help you Changing the water for the fish tank. This mini pump really sucks! This pump operates at 3V~9V and has enough suction for most small projects. Use this pump to make a fountain or waterfall, even water your plants!
If you are searching an ultrasonic ranging module, the HC-SR04 is good choice: Its stable performance and high ranging accuracy make it a popular module in electronic market. It's cheaper than an IR range finder with similar range accurancy and distance.