Author Archives: R-B

How to measure capacitance with a microcontroller?

Microcontrollers are widely used in measuring various physical variables. The techniques involved in the measurements could be different for individual variable type and are mostly based on the characteristics of the variables to be measured. This tutorial describes some methods for measuring the capacitance of a capacitor using microcontrollers. The techniques use the characteristics of the capacitor itself and are therefore universal and can be easily implemented with any microcontrollers.
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Where do I buy my electronics components from?

I have been living in Southern Virginia for past 3 years and I haven’t seen any retail store to shop for electronics components that are needed for my projects, except the Radioshack stores. I don’t prefer to go to Radioshack as the prices are much higher than my budget. A few years ago, I discovered an online store named Futurlec. I was surprised with their prices, their stuffs were really cheap and of good quality. I made 4 orders in the first year, and I was very happy with what I got. The only problem was they shipped their items from Thailand and the shipping was slow. I got my stuff usually in 3-4 weeks, which was not bad for me as I was not in rush to complete my projects. Read more

Heart rate measurement from fingertip


Heart rate measurement indicates the soundness of the human cardiovascular system. This project demonstrates a technique to measure the heart rate by sensing the variation of the blood volume inside a finger artery, which is caused by the pumping action of the heart. It consists of an infrared LED that transmits an IR signal through the fingertip of the subject.  A part of this infrared light is reflected by the blood cells. The reflected signal is detected by a photo diode sensor. The changing blood volume with heartbeat results in a train of pulses at the output of the photo diode, the magnitude of which is too small to be detected directly by a microcontroller. Therefore, a two-stage, high gain, active low pass filter is designed using two Operational Amplifiers (OpAmps) to filter and amplify the signal to appropriate voltage level so that the pulses can be counted by a microcontroller. The heart rate is displayed on a 3 digit seven segment LED display. The microcontroller used in this project is PIC16F628A.

Heart rate measuring device using PIC16F628A

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VGA monitor tester

If you are a computer technician and want to avoid the need of a PC on your desk to generate test rasters, this is something you need to build. This is an embedded monitor tester that you can use to test if a VGA monitor is working or not. You don’t need a bulky computer on your working desk anymore.

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