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

Arduino based pulse rate meter

Our pulse is direct indicator of physiological condition. It may be used to determine workout condition, health status, or even indicate when you are lying. You’ve probably seen that intensive care patients almost always have small thing on their finger which takes reading of of blood oxygenation and so the pulse. ASCAS in his instructable have built simple pulse meter device that connects directly to Arduino. He had put some effort to make sensor itself. He was looking for suitable clamp that would fit on finger and could carry detector circuit. He found that coat hanger has what it needs. He drilled small hole where he glued a red LED and on opposite side he placed LDR. Then he focused on software. He wanted to see pulse visually, so he wrote a Processing code to capture data from Arduino and display in nice graph. Continue reading

Building a pulse meter using ChipKIT

chipKIT is a great PIC32 based Arduino like development board designed by digilent. They have made quite a bunch of them since last time I have checked. Additionally they are taking care of numerous shields that allow quick and easy interfacing and developing cool things. Embedded-lab has been doing a nice chipKIT tutorial series. This time they are building a pulse meter using several building blocks – chipKIT Uno32, Basic I/O shield and Easy pulse sensor along with their Easy Pulse sensor board. Everything plugs in nicely while leaving soldering iron cold. Pulse waveform is captured with on Analog input and displayed on I/O shield graphical LCD. Program also calculates Beats Per Minute (BPM) value. Continue reading

Hacking Your E-Bike is Just A Piece of Cake!

You have an old-fashioned exercise bike that can’t show up any data when you’re peddling and exercise with it? You wish to make a little modification on it with a multi-meter connected to cables out of the exercise bike? Oh well, it’s time to have some fun with your exercise bike now… First thing first, find one cable from the front “wheel”, where it’s a cable that going up to the “computer”. Differential the handlebar sensors and the pulse meter, which the pulse meter works with reading the change in resistance of your skin. Then, you’re hooking the multi-meter to the cable from the wheel. You can set your connection to beep, when there was a connection detected by the multi-meter. You must make sure that both of them are beep, either you’re moving the pedals or the wheel is moving. After that, you cut the wire in two and hook those up to the Arduino. Remember to solder the largest resistor, which you can find in the electronic scrap box on one of the cables. Continue reading