Sensor Technology for Health and Fitness Applications


By Jon Gabay @

Determining the state of our health has always been a matter of finding a way to monitor and measure the body’s most basic functions. Before instrumentation, visual indicators were used that allowed us to know, for example, what our body temperature should be, what a healthy pulse is, and what an acceptable respiration rate is.

Today, with an aging population more people now need some sort of portable health monitoring, which could take the form of devices that, among other things, dispense medication at regular intervals, stimulate the heart, or measure blood sugar levels and inject insulin. This article looks at medical- and fitness-sensor technology—contacted and contact-less, placed on the skin, subcutaneous, or internal—that now or soon will be available to design engineers. All parts, tools, and data referenced here can be found on the Digi-Key website.

Sensor Technology for Health and Fitness Applications – [Link]

Website is Down Detector


by jckelley @

If you work in a company that has a website, you know how important it is that the website always be up and running. That’s why you constantly see “99.99999% reliability!” all over the fancy server hosting sites. A website can’t make money if the system is down, so knowing when that happens and reacting quickly is super important. In this Instructable, we will use the LinkIT ONE board to make an alert system that will play a loud alert siren and send us a text message. This way no matter where we are, we can respond as fast as possible!

Website is Down Detector – [Link]

How to Make an Internet Speed Analyzer


This is an internet speed Analyzer based on Raspberry Pi:

This application will run speedtest-cli against’s servers using cron. It will then email the results daily and weekly.

Also – using e-paper hat – you can utilize the buttons to run the speed-test manually and display the results to the screen.

To use the device you will need a few bits installed to your Raspberry Pi. You can see the full list below, but if you just want to get started, see the simple instruction below:

How to Make an Internet Speed Analyzer – [Link]

Lie Detector and Biofeedback Arduino Based


by masteruan @

This tutorial will explain how to build a machine for biofeedback. But first a bit of theory.

What is biofeedback?

Biofeedback is the process of gaining greater awareness of many physiological functions primarily using instruments that provide information on the activity of those same systems, with a goal of being able to manipulate them at will. Some of the processes that can be controlled include brainwaves, muscle tone, skin conductance, heart rate and painperception.
Biofeedback may be used to improve health, performance, and the physiological changes that often occur in conjunction with changes to thoughts, emotions, and behavior.

Lie Detector and Biofeedback Arduino Based – [Link]


Wrist Mount Digital Altimeter

This project is a simple wrist mount digital altimeter which is a device used to determine altitude. This design uses atmospheric pressure to calculate the altitude of its location. The lower the atmospheric pressure, the higher the altitude. The project is comprised of a microcontroller (MCU), an 84×84 pixel graphic LCD and a barometric pressure sensor.

The barometric pressure sensor used in the design is the MS560702BA03-50 from TE Connectivity Measurement Specialties. It consists of a piezo-resistive sensor and a sensor interface IC. Its main function is to convert the uncompensated analogue output voltage from the piezo-resistive pressure sensor to a 24-bit digital value, as well as providing a 24-bit digital value for the temperature of the sensor. It is optimized for altimeters and variometers with an altitude resolution of 20cm. The MS560702BA03-50 measures the atmospheric pressure on its location then converts it to a 24-bit value through its internal ADC. The sensor reading is then transmitted to the MCU through SPI. Then the MCU calculates the altitude by using the pressure reading. The calibration of an altimeter follows the equation z = cT log (Po /P), where c is a constant, T is the absolute temperature, P is the pressure at altitude z, and Po is the pressure at sea level. The calculated altitude is then displayed through an 84×84 pixel graphic LCD which is mostly found on old phones. The circuit is powered through a 3.3V battery.

The altimeter is used to aid navigation and is mostly used in skydiving, mountaineering and hiking applications. It is usually hand-held or in wrist-mount form for the ease of use. Altimeters can also be found in aircrafts such as planes and helicopters and others that needs altitude indication.

Wrist Mount Digital Altimeter – [Link]

Motorcycle custom instrument panel


Josh from Colorado build a nice dashboard for this motorcycle based on ATMega128 and EPSON S1D13700 LCD Screen:

Since the GSXR is now a street fighter the factory gauges won’t do, and I wanted something I could log air/fuel ratios with so I can jet the bike. I went a little overboard making a new dash.

I had a Planar 160×80 EL graphic display that’s been in my parts bin for years that I’ve always wanted to use, and this was perfect. Unfortunately it doesn’t have a controller so I had to interface it to the CPU with an Epson S1D13700 graphic controller. The display indicates speed from a GPS module, air/fuel ratios from the wideband O2 sensor, engine temp, battery voltage, time from GPS, and RPM. I used a light sensor to sense ambient brightness levels and dim the display by changing TC/R in the graphics controller. The refresh of the display is high enough to allow a large dimming range without flickering.

Motorcycle custom instrument panel – [Link]

Open Badge: The LED Badge


Rohit Gupta published a new build, the OpenBadge

The major elements on the PCB were:
– LED Matrix
– A MSP430G2553 microcontroller brain
– A ULN2803 Darlington Driver to sink the current
– A USB connector to charge the battery
– A SBW connector to program the MSP430
– A Switch to change the message
– A Li-Ion battery from a Discarded Phone
– Current limiting and Pull up resistors
– Decoupling Capacitors
– A REG1117 Regulator for MSP430

Open Badge: The LED Badge – [Link]


Portable GPS Data Logger

glg2 has build a portable GPS logger based on ATMega328 mcu:

I have built a GPS Logger and it works very well to trace the drove route for two years. By the way, the navigation solution computed by GPS receiver itself has an excellent accuracy without DGPS because an intentional offset added by US goverment has been stopped several years ago. The position error seems to be some meters under clear sky. It is a suffcient accuracy to trace the movement of walk. However that GPS logger was designed for only car use so that I re-designed a portable one.

Portable GPS Data Logger – [Link]


DIY milliohmmeter



This is an example of a simple and cheap milliohmmeter that can be made by every maker. The core of the circuit are a current source (LT3092) and a current sense (INA225): a costant current flows through the milliohm resistor under test and the voltage at the current sense output gives the value of the resistor (V=R*I).

The milliohmmeter can be used as a stand alone instrument by adding a MCU with at least 10 bit ADC and a LCD display or it can be used togheter with a DMM.

DIY milliohmmeter – [Link]

Anti-Drowsiness Alarm

This reference design is an anti-drowsiness alarm, which aims to keep the drivers alert by disrupting one’s drowse. According to the study by U. S. National Highway Traffic Safety Administration (NHTSA), drowsy driving is the primary contributor of at least 100,000 auto crashes a year. Statistics shows that most crashes caused by drowsy driving occur from midnight to 8:00 am. During these times, a person often goes to sleep since it is dark outside.

The light dependent resistor (LDR) and the transistors (Q2 and Q3) serve as switch that prevents the oscillation of CD4060 binary counter. When the LDR is exposed to light (i.e., daytime), Q3 conducts while Q2 does not. This makes the RESET pin of CD4060 high to prevent it from oscillating. At night, Q3 does not conduct while Q2 conducts and pulls the RESET pin of CD4060 to ground. This starts the oscillations of CD4060 as indicated by the flashing of LED6. The internal oscillator of binary counter CD4060 oscillates at a frequency based on the values of R8, R9 and C3. The sensitivity of the LDR can be adjusted by the potentiometer R12. When the Q13 (pin 3) output of CD4060 becomes high, the RESET pin (pin 4) of the NE555 becomes high and it starts oscillating. Its pulse rate can be slightly adjusted using the potentiometer R6. The pulsed output of NE555 is then fed to the clock input of CD4017. The CD4017 is a decade counter with ten outputs, but only one of its outputs is high at a time and all the other outputs remain low. The output from NE555 serves as clock for CD4017. As a result, the Q1 output of CD4017 becomes high at the first positive edge from NE555 after 50 seconds. After 6 minutes, the Q6 output goes high and LED4 glows for one minute and the warning buzzer sounds. If the circuit is not reset using push-to-switch 1977737-1 after hearing the warning beep from PZ1, the counting of CD4017 continues and at the end of the 10th minute, the Q9 output becomes high to activate CD4093.

This circuit is designed to keep the drivers awake while driving at night. This is done by sounding intermittent beeps and by emitting flashing light. As long as Q9 output of CD4017 remains high, CD4093 oscillates and the piezobuzzer beeps and the white LEDs flash with a frequency determined by the values of R3 and C1.

Anti-Drowsiness Alarm – [Link]