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Reading hear rate with piezo sensor

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. Continue reading

Simple Arduino based pulse sensor

Heart rate or pulse is one of important diagnostic and monitoring parameters in human body. If you are doing exercises you may also need to monitor heart rate in order to determine its effectiveness. Ohoilett shares pretty simple circuit that may be used to detect pulse. The idea here lies on simple method which is based on measuring passing light through the finger. In biomedical engineering this is called photoplethysmography. During one heart period blood is pumped through the body, so capillary volume increases and decreases periodically. By shining light through the finger we can detect its variation and so heart rate. In order to have reliable data wee need to condition incoming signal to Arduino input level. So there are couple operational amplifiers used where first one takes current signal from photodiode and converts it to voltage. This stage is called trans-impedance amplifier. Then signal is passed through high pass filter which is made of RC circuit. And last stage is gain stage, which amplifies signal to Arduino input level. All is left is to detect signal peaks within… Continue reading

Scanning your vitals with medical tricorder

Smart medical devices are coming closer to our daily lives. Times seems are passing when the only device we used at home was mercury based thermometer or manual blood pressure meter. Those devices are more or less automatic. Things are getting even better with wearable electronics. A simple wrist watch can monitor your pulse, pressure and temperature. MarkusB has been inspired by SciFi movies where heroes from Star Trek could self-diagnoze medical conditions within seconds. So he started a medical tricorder project. The device he built is able to measure temperature on the forehead with infrared thermometer and PPG (Photoplethysmograph) pulse/heart rate on ear lobe. He found that reading only those two parameters he could read lots of medical parameters. To call a device tricorder there is one more sensor needed. So he intends to add respiration sensor to read breathing rate by using mask and pressure sensor like MPXV4006GP. He built a custom Arduino board with OLED display. Microcontroller does some intense calculations to evaluate medical parameters out of readings. Of course it cannot be considered as reliable medical… Continue reading

Graphing heart rate with Arduino

If you enjoy exercises probably it is interesting to analyze some parameters like heart rate. The easiest way is to purchase heart rate monitor like wearable Polar chest strap that sends data wireless. Anyway commercial solutions usually don’t offer much flexibility like transfering data to computer or have full access to data log. So Wolf decided to tweak around with polar transmitter. For this he used a separately purchased receiver from SparkFun that simply picks up heart beat pulses sent wireless. When connected to Arduino this becomes really wide open for modifications. Right now it simply displays averaged heart rate data on 2.8” LCD screen. Also heart beat data is logged to microSD card in a CSV file. Lack of RTC chip makes it quite difficult to keep track of history so there is a space for improvements. Hopefully we will see more durable and accurate version. Continue reading