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

Non-IR LEDs as Sensors

All of us know that IR Leds are widely used as sensors in different type of bots. However this project aims at using normal Led’s as sensor. Due to the semiconductor properties of LEDs they are capable of detecting light in the same or close to the wavelength they would normally emit. However the problem is the voltage produced is so less, that accuracy gets compromised. The algorithm is really easy to implement. According to the algorithm you first make all the analog input as output and pull all the pins to low so all led’s light up.  One by one you one pin analog input while making the other sets of led’s glow as a normal gpio pin.  After you have read all the input, adjust the PWM of blue led based on the amount of light that was measured and this process continues forever. It’s a must do project if you have started to learn Arduino as it will expose you with the concept of PWM and ADC. Continue reading

Digital clock with discrete diodes

Building digital clocks is some sort of “Hello World!” project to most embedded hobbyists. And you can find tons of them with various displays and microcontrollers. But there is always a room for something different and unusual. So if you have spare 130 LEDs you can do same easily. The guy, who calls himself Syst3mX in instructables, has built a digital clock by using discrete LEDs and Arduino. He made something similar to seven segment display where distinct LEDs are aligned and controlled like it. Of course lighting up such a bunch of diodes requires more power so each segment is driven by transistor. The overall effect looks really great Continue reading