Tag Archives: detector

iEAT – A Powerful Keychain Detector To Detect Food Allergens

For kids and adults with food allergies, having meals from restaurants or hotels can sometimes be very risky. Even when ultimate care is taken, freshly prepared meals can accidentally become cross-contaminated with an offending food and trigger an allergic reaction. Every year many people end up in the emergency room due to food allergies. Researchers of the Harvard Medical School developed an affordable device called iEAT for detecting allergens, which can reduce the anxiety of the people prone to allergies.

iEAT - A Portable allergen-detection system
iEAT – A Portable allergen-detection system

Conventional methods to detect the hidden allergens require massive laboratory equipment. They are slow and also do not work on a low concentration of allergens. Ralph Weissleder, Hakho Lee, and their colleagues at the Harvard Medical School wanted to make a more practical, consumer-friendly alternative. They reported in the journal ACS Nano the development of a new portable allergen-detection system that features a keychain analyzer for detecting allergens in food anywhere, anytime.

The portable allergen-detection system called integrated exogenous antigen testing or iEAT is small enough to fit in your pocket and it costs $40 only. The iEAT consists of a handheld device to extract allergens from food and an electronic keychain reader for sensing allergens. Then, the result is wirelessly sent to a smartphone. The prototype is able to detect five allergens within 10 minutes, one each from wheat, peanuts, hazelnuts, milk, and egg whites, even if they are in very low concentration.

The main device uses a disposable sample collector which is inserted into the small-sized main unit. The device is so sensitive that the scientists were able to detect gluten in foods advertised as being “gluten-free”. For example, the device detected gluten in salad and an egg protein in beer. Although the prototype was primarily designed to sense five allergens only, the researchers say the device could be expanded to test for many additional compounds, including other allergens and non-food contaminants such as pesticides.

Nuclear physics applied in smoke detectors

by robertgawron.blogspot.com:

Not many people know, but in some smoke detectors, radioactive materials play an essential role. Today I will present one of those devices, and my -successful- attempt to reverse engineer it and get the circuit diagram.

Nuclear physics applied in smoke detectors – [Link]

IRis – An Infrared Sensor using Photodiode amplification Circuit


[devttys0] designed a sensitive IR detector for capturing weak infrared signals. He shared in detail how he designed the circuit, beginning from the basic components, walking through solving the problems and finally ended up with a complete working circuit.

Craig Heffner/[devttys0] built this circuit for a friend’s Defcon talk, Blinded by the Light, the talk concerned about the emitted IR signals from the IR proximity detector in our devices like mobiles, and how we can identify the type of the device/OS using these signals.

Craig wanted to build a general purpose IR detector to capture and analysis the raw IR transmissions where IR receivers is designed to sense the modulated IR signals at 36-38 kHz. “But there is so much more to the world of IR than this” Craig said.

The first basic idea in the design is to use transimpedance amplifier which is basically a current-to-voltage converter.
When photons strike the photo diode, it will actually emit charge carriers, so the output of this sensor is a current. The output voltage (Vout= Ip*Rf) is linear in respect to the current.


The major problem with this particular configuration is the unwanted high frequency oscillation, so a capacitor was added in parallel with the feedback resistor.


The next problem solved by Craig, is the saturation of the amplifier in high and low side by adding some bias resistors just to keep the reference voltage of the positive input of the op-amp at just under 200 millivolts.

To prevent saturation in high side he added three diodes, in fact three JFETs configured as diode, in the feedback path. The reason of using JFET configured as a diode is that it has less leakage current than normal silicon diodes, so when the voltage exceeds 3*0.7=2.1V then they short the feedback resistor, this point is important in our design because it has a current flow from photo diode.

The last thing to solve in first stage of the design is the problem of constant current from ambient light, which will generate a DC component in the output. So Craig added a high pass filter in the output.


Now the circuit will still have some analog signals in output, noise and some negative spikes. So he cleaned things up by using a comparator with a Schottky diode in the non-inverting input to omit the negative pulses less than 0.2 Volt.


To see the full details of the design you can see the video below, and also you can reach the design files (SCH & PCB) over Github.

In addition, you can see the references pointed by Craig in his site analogzoo.

Arduino Lightning Detector


This is an Arduino tutorial on how to detect lightning from far away.

In this tutorial, we will build a lightning detector using an Arduino Uno, a few resistors and some jumper wires. Most lightning detectors often cost too much for the normal hobbyist, however this does not mean one cannot enjoy lightning detection and the physics behind it. In this tutorial, using a surprisingly simple circuit we will be able to detect lightnings from around 10-20 km away, which is to say the least impressive.

Arduino Lightning Detector – [Link]

Internet-Connected Migrane or Allergies Detector


adafruit has published an IoT  Migrane or Allergies Detector. This project uses Feather HUZZAH ESP8266 wireless microcontroller board to pull a forecast from the accuweather.com web site, then distills this to its barest essence: good news or bad news?

An ambient information display is an indicator which conveys meaningful data non-verbally. Unlike a computer screen which must be actively read, an ambient display needs no mental “mode shift” to interpret, and often just sits in one’s peripheral vision. The low fuel light on a car’s dashboard is an example of an ambient display.

Internet-Connected Migrane or Allergies Detector – [Link]

Website is Down Detector


by jckelley @ instructables.com:

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]

Lie Detector and Biofeedback Arduino Based


by masteruan @ instructables.com:

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]

DIY WiFi gas detector with text alerts


Stefan over at Hackster.io has written an article detailing his DIY Wi-Fi gas detector that sends SMS alerts:

Hey guys, back with another little project that I’ve been fiddling with for the past week. With kids around, every parent is thinking how to make their home safer for the little ones and for everybody in general. One of the most dangerous thing in the house can be the stove and since we have a gas-powered one, I always wondered why there are no simple gas detectors that can be used around the stove, just to alert instantly that gas may be leaking.
Well, that was the moment when I decided to build one of my own. Having a Particle (Spark) Photon lying around, I decided to use that as a foundation for the project. I like the fact that they are very small and cheap, and also can be flashed over the Wi-Fi. Having that settled, I needed the gas sensor and some kind of alerting system.

DIY WiFi gas detector with text alerts – [Link]

Passive Infrared Detector Circuit

The infrared (IR) is invisible radiant energy, electromagnetic radiation that we cannot see with our eyes, but we can sometimes feel on our skin as heat. The infrared light falls just outside the visible spectrum, beyond the edge of what we can see as red. Most of the thermal radiation emitted by objects near room temperature is infrared.

The circuit uses a MCP6032 microchip operational amplifier. The MCP6032 operational amplifier (op amp) has a gain bandwidth of 10kHz with a low typical operating current of 900nA and an offset voltage that is less than 150uV. The MCP6032 uses Microchip’s advanced CMOS technology, which provides low bias current, high-speed operation, high open-loop gain and rail-to-rail input and output swing. The MCP6032 operates with a single supply voltage that can be as low as 1.8V, while drawing less than 1uA of quiescent current. The MCP6032 is available in standard 8-lead SOIC and MSOP packages. It also includes, a PID20 integrated circuit and a few electronic components. The size of the output signal of PID20 is determined by the task at pins 3 and 4. The output signal at pin 3 is compared with a reference voltage equal to half the supply voltage. The reference voltage is taken from the voltage divider R2-R3-R4-R5. When approaching an object warmer than the surrounding environment, or to remove an object colder than the environment, the output voltage increases. The variation of the sensor output will be compared, the IC2a and IC2b, located voltage of 0.5V under and over voltage reference respectively. Depending on the output, one of the comparators calculates and activates T1.

This basic circuit is used in night-vision devices with infrared illumination, which allows people or animals to be observed without the observer being detected. The infrared light is also used in industrial, scientific, and medical applications as well as in consumer devices.

Passive Infrared Detector Circuit – [Link]