Heart rate is one of many important physiological parameters. It can be an indicator of workout intensity, stress, and even decease. With heart rate information you can do many interesting signal processing experiments like detecting its variations, or even fuse with other physiological data. There are several ways of getting heart rate data. One well known method is by using LED and its light pass variations through finger (pulse-oxymetry). Ohhitch have tried to attache piezo sensor to finger and found out that it detects heart rate very well.
Piezo sensor was connected to Arduino analog input which reads voltage differences due to blood flow pressure changes. This is enough to get reliable data. Simple Arduino code reads analog value and applies simple thresholding procedure which calculates heart rate in bpm.
Bitcoin is an online currency which uses peer-to-peer technology for payment transfers. Its price is varying over time and if you have some investments in Bitcoins, you should keep an eye on it. Rui Santos suggests using ESP8266 programmable WiFi module to check Bitcoin price. The idea is pretty simple. He programmed WiFi module as HTTP client which regularly requests Bitcoin price by using JSON API.
ESP8266 is fairly to program. All you need is to flash it with NodeMCU firmware which then allows programming module with LUA script which is somewhat similar to Arduino concept. With only few lines of code you can connect to internet, control GPIO and do other crazy things. This following script can be used as base for other HTTP client projects like weather, finances or other extraction.
Oscilloscope is one of most important test devices in electronics. If your needs are not very high, you can go with any cheap or DIY scope. But in the end I would recommend getting standard bench oscilloscope. It saves time and eventually money. If you currently have low budget for purchasing scope, then take a look at this following scope project where vaupell builds it with Arduino Mega and TFT display.
Scope project is mostly glued out of two sources where one deals with Arduino scope functionality and another with TFT display. The end result looks great and serves the needs.