sensing the imperceptible

Temperature Sensor - LM335A

Digital Temperature & Humidity sensorshtt

p://w

ww.el

echo

use.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=g

srvT2

odicI

http:/

/www

.spar

kfun.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=d

Fq7B

F_kju

s&fea

ture=

relat

edsensing the imperceptible:

temperature

Temperature sensors read environmental tem-perature with varying degrees of accuracy. They are availabe both in digital and analog versions as well as Celsius and Farenheit.

A standard digital temperature sensor is the LM335A. It is a very easy-to-use analog temperature sensor. The LM335A works like a Zener diode with a breakdown voltage proportional to absolute tempera-ture at 10mV/°K. Hook up a resistor from 5V and GND, and the LM335A will output an analog voltage of 2.98V (298 Kelvin is 25C or room temperature). The output of the sensor is linear, and when calibrated at 25°C the LM335A has typically less than 1°C error over a 100°C temperature range. The sensor can operate continuously from −40°C to 100°C.Calibration of the sensor requires a pot connected across the sensor, with the wiper of the potentiometer connected to the adjustment pin of the LM335.

There also exists a combined temperature and humidity sensor, although it is a bit more expen-sive. Some temperature sensors come soldered to a mini breadboard and are called Temperature Sens-ing Bricks that can be used without an Arduino Board. Most of the available temperature sensors are under 10$, depending on whether or not they have attached circuitry and those paired with humidity are much more expensive.

CH.09 CH.08 CH.07 CH.06 CH.05 CH.04 CH.03 CH.02 CH.01

Barometric Pressure Sensor

Barometric Pressure Sensor

http:/

/www

.spar

kfun.c

omRe

levan

t you

tube v

ideo w

ebad

dres

shtt

p://w

ww.sp

arkfu

n.com

Relev

ant y

outub

e vide

o web

addr

ess

sensing the imperceptible:

barometric pressure

A barometer measures barometric pressure, also known as atmospheric pressure. The Barometric Pressure Sensor MEMs - SCP1000-D01 This is the very fi rst absolute pressure sensor on the market to use MEMs technology to grant 17-bit resolution. Un-der ideal conditions, this sensor can detect the pres-sure difference within a 9cm column of air. Breakout board available below!

VTI’s SCP1000-D01 digital absolute pressure sensors are intended for barometric pressure measure-ment and altimeter applications for 30kPa...120kPa and -20°C...70°C measuring ranges. The pressure and temperature output data is calibrated and com-pensated internally and the communication between the SCP1000 and its host micro-controller is realized using an SPI interface.

SCP1000 is comprised of a VTI’s 3D-MEMS capacitive sensing element, a dedicated low power CMOS interface ASIC with on-chip calibration mem-ory, 4 preset measuring modes and a LCP (Liquid Crystal Plastic) MID (Molded Interconnect Device) housing. The component is a surface mountable de-vice incorporating a circular vertical wall for easy wa-terproof sealing.

A less expensive barometer is the MPL115A1, which is a digital barometric pressure sensor that uses MEMs technology to give accurate pressure measurements between 50kPa and 115kPa.

HS1101 Humidity Sensor

HIH-4030 Humidity Sensor

http:/

/www

.spar

kfun.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=n

cPay

JZyN

_whtt

p://w

ww.pa

ralla

x.com


humidity

Humidity sensors detect relative humidity and are often combinded with temperature sensors. A common stand alone humidity sensor is the HS1101 humidity sensor. Based on a unique capacitive cell, these relative humidity sensors are designed for high volume, cost sensitive applications such as offi ce au-tomation, automotive cabin air control, home appli-ances, and industrial process control systems. They are also useful in all applications where humidity com-pensation is needed.

Also availabe are humidity sensors already sol-dered to boards. An example is this breakout board for Honeywell’s HIH-4030 humidity sensor. The HIH-4030 measures relative humidity (%RH) and delivers it as an analog output voltage. You can connect the output of the sensor directly to an ADC on a microcontroller; and, thanks to the sensor’s near linear voltage output, the data is very easy to process. Voltage applied to the supply pins should be within 4-5.8VDC, and op-timally at 5V. The sensor will typically only consume about 200μA. This product comes as shown in the picture, with the HIH-4030 soldered onto the break-out board. The pins of the 3-pin header are spaced by 0.1”.

Humidity sensors are a little more expensive than temperature ones, particularly if they are at-tached to a board.

CH.09 CH.08 CH.07 CH.06 CH.05 CH.04 CH.03 CH.02 CH.01CH.09 CH.08 CH.07 CH.06 CH.05 CH.04 CH.03 CH.02 CH.01

USB Weather Board

Weather Meter

http:/

/www

.spar

kfun.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=N

HkaZ

8O-R

9Ihtt

p://w

ww.sp

arkfu

n.com


weather

Weather sensors exist that combine several different sensors in a single unit. One example of this is the USB Weather Board. We take the sensi-tive SCP1000 barometric pressure sensor, add the TEMT6000 ambient light sensor, match it with a sensitive SHT15 humidity sensor, and we give you weather over USB! Ok, so it doesn’t really predict the weather, but you can immediately tell what the current pressure, humidity, ambient light level, and temperature is. Graphed over time you can watch weather fronts move in and the rain come down. This new version uses and ATmega328 instead of the ATmega168. Code is interchangeable between the two. Serial output is a single visible ASCII string at 9600bps.Features:* Powered over USB or externally* Absolute barometric pressure accurate within +/-150 Pascal* Relative humidity accurate within +/-2%* Temperature accurate within +/-0.3 degrees C* Ambient light sensor (analog level)* Serial output 9600bps 8-N-1* Measurement rate of 1Hz* Sensors are isolated from all potential heat sources* Firmware allows for temperature compensation

The utube video at left also shows how you can use Arduino to pick up the data from a weather station module, like the Weather Meter at left, which costs about $125.

Thermal Anemometer Thermistor

INSPEED VORTEX ANEMOMETER

http:/

/www

.insp

eed.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=X

mkRH

Lfwqb

0htt

p://w

ww.m

oder

ndev

ice.co

m/


wind

A sensor for detecting wind is called an an-emometer. Based on original research, “The Wind Sensor” is a thermal anemometer based on a tradi-tional technique for measuring wind speed. The tech-nique is called the “hot-wire” technique, and involves heating an element to a constant temperature and then measuring the electrical power that is required to maintain the heated element at temperature as the wind changes. This measured electrical input is then directly proportional to the wind speed. Hot wire an-emometers are available in hand-held packages re-sembling multimeters, but this is the fi rst small sensor suitable for electronic experiments.

Our wind sensor has an offi cial name of TAT for “Thermal Anemometer Thermistor”, a nod to the fact that the hot-wire in our sensor has been replaced by a solid state sensor called a thermistor.

The TAT will work fi ne outdoors but for higher wind speeds the spinning cup style anemometers will probably excel, just because the electrical input avail-able to the TAT is limited somewhat by its supply volt-age. The board has an op-amp on it that will work with a supply as high as 12 volts, but it was really designed for, and is calibrated at the factory for, fi ve volts.

Another sensor is this rugged anemometer with dual digital display handles speeds from 3 mph to over 125 mph. Comes with exterior grade wire. The Pole Mount anemometer is great for home or mobile use where AC power is not available. It costs $79, Pole not included.

CH.01 CH.02 CH.03 CH.04 CH.05 CH.06 CH.07 CH.08 CH.09 CH.09 CH.08 CH.07 CH.06 CH.05 CH.04 CH.03 CH.02 CH.01

Image Caption

Infrared Proximity Sensor Long Range

http:/

/www

.spar

kfun.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=la

G8p6

DXoe

M&fea

ture=

relat

edhtt

p://w

ww.sp

arkfu

n.com

http:/

/www

.youtu

be.co

m/wa

tch?v

=ELe

OApO

C7Hw


ifrared

There are long and short range infrared sensors for detecting proximity as well as emitting and detect-ing IR sensors. The common sensors are pictured at left and range from $2-$15. The detectors and emit-ters can be purchased individually or as pairs. These sensors are often used for line following robots, for example the MIT Handy Board Microcontroller. See http://www.leang.com/robotics/info/articles/linesen/in-dex.html

Another IR application is to measure temper-ature. Melexis’ MLX90614ESF-BAA is an infrared thermometer designed for non-contact temperature sensing. An internal 17-bit ADC and a powerful DSP contribute to the MLX90614’s high accuracy and reso-lution. It has a huge number of applications including body temperature measurment and movement detec-tion. The MLX90614 provides two methods of output: PWM and SMBus (i.e. TWI, I2C). The 10-bit PWM output provides a resolution of 0.14°C, while the TWI interface has a resolution of 0.02°C. The MLX90614 is factory calibrated in wide temperature ranges: -40 to 85°C for the ambient temperature and -70 to 382.2°C for the object temperature. The measured value is the average temperature of all objects in the Field Of View of the sensor. The MLX90614 offers a standard accu-racy of 0.5°C around room temperatures

TCS230D Color Sensor

ColorPal

http:/

/www

.para

llax.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=W

bmYc

dXjvJ

M&fea

ture=

relat

edhtt

p://w

ww.el

echo

use.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=K

yQOy

wvM1

RE&f

eatur

e=re

lated


color

The TCS230D Color Sensor is an example of available technology for sensing color. The TCS230 programmable frequency converter color light/red, green and blue fi lter integrates in single chip, so it can be realized without ADC each color channel 10 more resolution. Chip contains a cross-connection 8 x 8 photoelectric diode array, each one of 16 diode pro-vides a color type, red, blue, green and remove all four types of optical information can maximize reduce inci-dent light inhomogeneity of radiation. With the color of all 16 photoelectric diode are parallel connection, work through the programmable foot to dynamically select color, to increase the accuracy and simplifi ed optical circuit. The chip USES 8 pin SOIC surface encapsula-tion, suitable for measuring the colorimeter.

Another option is the ColorPAL from Parallax. It is a miniature color and light sensor which, through its RGB LED, doubles as a color generator. For sens-ing color, the ColorPAL uses its LED to illuminate a sample, one color component at a time, along with a broad-spectrum light-to-voltage converter to measure the light refl ected back. The amount of light refl ected from the sample under illumination from each red, green, and blue LED can be used to determine the sample’s color.


human body IR Pyroelectricity sensor

Human infrared sensor module

http:/

/www

.elec

hous

e.com

Relev

ant y

outub

e vide

o web

addr

ess

http:/

/www

.elec

hous

e.com

Relev

ant y

outub

e vide

o web

addr

ess


ir heat detection

There is something called an IR Pyroelectricity sensor which uses IR to dectect changing heat levels and therefore the presence of a human being. The RE200B CAN-3 human body IR Pyroelectricity sensor is one such sensor available cheaply from elehouse.

They also make another kind of IR sensor attached to a breadboard; also used to detect hu-man presence. Using PIR pyroelectric sensor, low power consumption, the authors 50uA wide range of static, DC voltage circuit small volume 4.5 --20V size38*28mm32 * 24 mm) can repeat/unrepeatable choice is simple to use and triggered power + - sig-nal output induction distance seven meters induction Angle 110 degree.

Pyroelectric infrared switch is a passive infrared switch which consists of BISS0001 ,pyroelectric infra-red sensors and a few external components. It can automatically open all kinds of equipments, inculding incandescent lamp, fl uorescent lamp, intercom, auto-matic, electric fan, dryer and automatic washing ma-chine, etc.

It is widely used in enterprises, hotels, stores, and corridor and other sensitive area for automatical lamplight, lighting and alarm system.


Thermocouple Type-K Glass Braid Insulated - K

Thermocouple Amplifier AD595-AQ

http:/

/www

.spar

kfun.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=m

8tHF7

55K6

ohtt

p://w

ww.ad

afruit

.com

http:/

/www

.youtu

be.co

m/wa

tch?v

=IMd

zfVsh

FFg&

featur

e=re

latedsensing the imperceptible:

heat

One way of detecting air and surface tempera-tures is with a thermocouple. Thermocouples are best used for measuring temperatures that can go above 100 degC. This is a bare wires bead-probe which can measure air or surface temperatures. Most inexpen-sive thermocouples have a vinyl covering which can melt at around 200 degC, this one uses a fi berglass braid so it can be used in high temperature measure-ments such as heaters and ovens.

An amplifi er can be used along with a thermo-couple, for example, the Analog Devices Thermocou-ple Type-K Amplifi er. Attach a thermocouple, 5V pow-er, and a decoupling capacitor and you’ve got 10mV/C output! The Thermocouple Amplifi er AD595-AQ is perfect for high temperature application. The 10mV/C analog output interfaces nicely with 10-bit ADCs found on many types of microcontrollers.


DETECTOR/AMP UV

Photodiode

http:/

/sear

ch.di

gikey

.com

http:/

/sear

ch.di

gikey

.com


uv sensing

A photodiode is a type of photodetector capable of converting light into either current or voltage, de-pending upon the mode of operation.

Photodiodes are similar to regular semiconduc-tor diodes except that they may be either exposed (to detect vacuum UV or X-rays) or packaged with a win-dow or optical fi ber connection to allow light to reach the sensitive part of the device. Many diodes designed for use specifi cally as a photodiode will also use a PIN junction rather than the typical PN junction.

A photodiode is a PN junction or PIN structure. When a photon of suffi cient energy strikes the diode, it excites an electron, thereby creating a free electron and a (positively charged electron) hole. If the absorp-tion occurs in the junction’s depletion region, or one diffusion length away from it, these carriers are swept from the junction by the built-in fi eld of the depletion region. Thus holes move toward the anode, and elec-trons toward the cathode, and a photocurrent is pro-duced. http://en.wikipedia.org/wiki/Photodiode

Two different kinds of UV sensors are available at digikey.com and are pictured at right.


from Technology Daily

CMOS IR Camera Module - 500x582

http:/

/www

.spar

kfun.c

omRe

levan

t you

tube v

ideo w

ebad

dres

shtt

p://w

ww.te

chma

gdail

y.com

/categ

ory/s

cienc

e/pag

e/40

http:/

/www

.instr

uctab

les.co

m/id/

Infra

red-

IR-W

ebca

m/


ir heat detection photography

Infrared radiation can be used to remotely de-termine the temperature of objects (if the emissivity is known). This is termed thermography, or in the case of very hot objects in the NIR or visible it is termed pyrometry. Thermography (thermal imaging) is main-ly used in military and industrial applications but the technology is reaching the public market in the form of infrared cameras on cars due to the massively re-duced production costs.

The instructables link at right shows you how to modify a standard webcam to catch the infrared spec-trum rather than the visible light one.

Sparkfun offers this is a high-quality black and white CMOS camera module with high-power infra-red LEDs to light up the night. Power the CA-84AC module, hook up any display, monitor, or LCD screen with an RCA input and get vivid black and white video at 500x582 resolution even in completely dark envi-ronments. Module is easily mountable and should be powered close to the 12V spec. Comes with high qual-ity optics, all the on board circuitry to output RCA sig-nal, and cable harness.



Lie Detector circuit

Ambulatory Blood Pressure Monitor

http:/

/www

.phoe

nix.tc

-ieee

.org/0

04_P

iezo_

Film_

Bloo

d_Flo

w_Se

nsor

/Ph

oenix

_Piez

oPuls

e.htm

Relev

ant y

outub

e vide

o web

addr

ess

http:/

/detec

tor-se

nsor.

blogs

pot.c

omRe

levan

t you

tube v

ideo w

ebad

dres

s


body sensing

This detector circuit is for detecting a Lie. The lie detector circuit diagram consists of three transis-tors, a capacitor, two lights or LEDs, fi ve resistors, and a variable resistor.

This Lie Detector circuit is based on the fact that a person’s skin resistance changes when they sweat (sweating because they’re lying). Dry skin has a resis-tance of about 1 million ohms, whereas the resistance of moist skin is reduced by a factor of ten or more.

Another way to sense things in the body is this piezo pulse sensor. The purpose of the piezo fi lm pulse sensor project is to identify and build a reliable, low power, low cost blood fl ow sensor. The sensor is intended for two proposed designs for the ambulatory blood pressure monitor (ABPM). They are: (a) an os-cillometric cuff design (as a Korotkoff sound sensor) and (b) the blood fl ow velocity design.

There are many other body sensors as in those used in medical devices, but there are not so many of these commercially availabe to use with Arduino.


Polar Heart Rate Module - RMCM01

Polar Heart Rate Monitor Interface

http:/

/www

.spar

kfun.c

omhtt

p://w

ww.sp

arkfu

n.com


human pulse

This Polar Heart Rate Module - RMCM01 can be used to detect the human heart beat. This is a OEM module for the Polar Heart Rate system. This device works with any Polar heart rate strap to pickup the electromagnetic pulse and output a 1ms pulse indicating a heart beat has occurred.Features:* Multiple interfaces: USB, Logic-level serial and I2C* Dual heart rate processing algorithms: averaged and raw* Uses the RMCM01 Polar OEM receiver* Compatible with coded and non-coded Polar trans-mitters including T31, T31C, T61C and Wearlink®* 32-entry heart rate data history buffer* Four 8-bit ADC inputs* Up to a 5 channel digital input/output utility port* Simple command/response interface* Programmable power-on default operation* Only works with one transmitter (HRM) in range

An accesory to this module is Polar Heart Rate Monitor Interface. This is a wonderful evalua-tion board cooperatively designed by danjuliodesigns and SparkFun. The Heart Rate Monitor Interface (HRMI) is an intelligent peripheral device that con-verts the ECG signal from the Polar Heart Rate Monitor (HRM) into easy-to-use heart rate data. It implements a sophisticated algorithm for computing an average heart rate even with noisy or intermittent data from the transmitter.

Alcohol Gas Sensor MQ-3

Piezo Respiratory Belt Transducer

http:/

/www

.spar

kfun.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=E

NO0M

lXLV

2c&f

eatur

e=re

lated

http:/

/www

.adins

trume

nts.co

m


breath

One way of sensing breath is to measure ac-tualy breathing rhythms. The Respiratory Belt Trans-ducer contains a piezo-electric device that responds linearly to changes in length. The transducer comes with a 6 meter cable and is MR Safe. It measures changes in thoracic or abdominal circumference dur-ing respiration. These measurements can indicate inhalation, expiration and breathing strength and can be used to derive breathing rate. The transducer may be used to characterize breathing patterns. The trans-ducer is a solid-state device that requires no excitation and connects directly to a BNC on any PowerLab. It is comfortable to wear, rugged, reliable and washable. It is suitable for use on animals of various sizes (from cats to horses) as well as humans.

Another way to sense human breath is through the detection of certain components. The Alcohol Gas Sensor MQ-3 is an alcohol sensor suitable for detect-ing alcohol concentration on your breath, just like your common breathalyzer. It has a high sensitivity and fast response time. Sensor provides an analog resistive output based on alcohol concentration. The drive cir-cuit is very simple, all it needs is one resistor. A simple interface could be a 0-3.3V ADC.

MQ-7 Carbon Monoxide Gas Sensor

MQ-5 Gas Sensor

http:/

/www

.elec

hous

e.com

http:/

/www

.elec

hous

e.com


chemicals

Another way to sense human breath is through the detection of Carbon Monoxide which is present in a person’s exhale. This sensor has a high sensitivity and fast response time. The sensor’s output is an ana-log resistance. The drive circuit is very simple; all you need to do is power the heater coil with 5V, add a load resistance, and connect the output to an ADC.

Other chemicals which can be detected using various sensors are methane, natural gas, liquid gas, kerosene, isobutane, propane, liquefi ed petroleum gas, and hydrogen. Many of these sensors assert that they have the ability to ignore noise such as alcohol and smoke in trying to detect other specifi c gasses. One such sensor, shown at bottom right, can detect natural gas , liquid gas, and kerosene but avoids the noise of alcohol and cooking fumes and cigarette smoke.

All of these gas sensors should be used with caution as there are heat coils located within the sen-sors that get rather hot.


Arduino pH meter

Phidget Ph Sensor

http:/

/www

.activ

e-ro

bots.

com

http:/

/www

.elec

tronic

s-lab

.com/

blog/?

p=36

76


PH sensing

The pH sensor components are usually com-bined into one device called a combination pH elec-trode. The measuring electrode is usually glass and quite fragile. Recent developments have replaced the glass with more durable solid-state sensors. The pre-amplifi er is a signal-conditioning device. It takes the high-impedance pH electrode signal and changes it into alow impedance signal which the analyser or transmitter can accept. The preamplifi er also strength-ens and stabilizes the signal, making it less suscep-tible to electrical noise

There is a link at right to an open software open hardware pH meter using an Arduino/Freeduino board. In other words, this is an electronic circuit to be connected with a glass electrode pH sensor.

If you don’t want to wire your own pH sensor but just want to transmit data readings directly into your computer, you can us this phidget. Connect any stan-dard Ph probe to this PhidgetPhSensor and quickly read Ph levels into your PC.


Geiger Counter

Geiger Tube

http:/

/www

.spar

kfun.c

omhtt

p://w

ww.yo

utube

.com/

watch

?v=9

m9Of

kQ6Z

qohtt

p://w

ww.sp

arkfu

n.com


chemicals (cont.)

Need to test for nuclear fallout? This is a USB powered Geiger Counter equipped with an AT-Mega328 that can be programmed in circuit using one of the programmers below. Simply plug the unit into USB (make sure you have FTDI drivers installed), open a terminal program to the correct COM port at 9600bps, and you will see random bits being gener-ated from the random background radiation.

Geiger tubes are the sensing elements of Gei-ger counters, which are used to measure ionizing ra-diation. This tube is made of a thin-walled stainless steel and is fi lled with a mixture of Neon and Halogen gases at low-pressure.

You’ll need a large voltage to get the Geiger tube to going - 325VDC minimum, 500VDC recom-mended. If ionizing radiation passes through the tube, short pulses of current will fl ow from the negative electrode to the positive electrode to be measured or counted.


Optical Dust Sensor - GP2Y1010AU0F

http:/

/www

.lynx

motio

n.com

http:/

/www

.spar

kfun.c

om

http:/

/parts

.digik

ey.co

m


particulate

Sharp’s GP2Y1010AU0F is an optical air qual-ity sensor, designed to sense dust particles. An infra-red emitting diode and a phototransistor are diagonal-ly arrraanged into this device, to allow it to detect the refl ected light of dust in air. It is especially effective in detecting very fi ne particles like cigarette smoke, and is commonly used in air purifi er systems.

The sensor has a very low current consump-tion (20mA max, 11mA typical), and can be powered with up to 7VDC. The output of the sensor is an ana-log voltage proportional to the measured dust density, with a sensitivity of 0.5V/0.1mg/m3.


Ultrasonic Range Finder


ultrasound

Ultrasound is cyclic sound pressure with a fre-quency greater than the upper limit of human hearing. Although this limit varies from person to person, it is approximately 20 kilohertz (20,000 hertz) in healthy, young adults and thus, 20 kHz serves as a useful low-er limit in describing ultrasound.

One sensor for dectecting this imperceptible sense is the Ultrasonic Range Finder - Maxbotix LV-EZ3. The sensor provides very accurate readings of 0 to 255 inches (0 to 6.45m) in 1 inch increments with little or no dead zone!

A model often used in building robots is the Ping Ultrasonic Range Sensor which prevents robots from running into things.

Ping))) Ultrasonic Range Sensor

Compass 2-Axis Integrated Solution

HMC6352 Compass Module

http:/

/www

.para

llax.c

omhtt

p://w

ww.sp

arkfu

n.com


compass

The Honeywell HMC6352 is a fully integrated compass module that combines 2-axis magneto-resistive sensors with the required analog and digi-tal support circuits, and algorithms for heading com-putation. Rumor is that Honeywell took all the tricks up their sleeve and created the HMC6352 using the HMC1052 core, a Microchip PIC core, and a combi-nation of MOSFET and OpAmp circuitry. This chip is simple to use and gives you magnetic heading down to the last degree.

Another model, the HMC6352 Compass Mod-ule, is fully integrated and combines 2-axis magneto-resistive sensors with the required analog, digital, microprocessor and algorithms required for heading computation.

The HMC6352 Compass Module provides a direct heading angle and includes internal calibration algorithms within its fi rmware. Stray magnetic fi eld protection and temperature compensation are also included.


hall effect sensor

mini hall effect sensor

http:/

/parts

.digik

ey.co

mhtt

p://w

ww.sp

arkfu

n.com


hall effect sensor

A Hall effect sensor is a transducer that varies its output voltage in response to changes in magnetic fi eld. Hall sensors are used for proximity switching, positioning, speed detection, and current sensing ap-plications.

In its simplest form, the sensor operates as an analogue transducer, directly returning a voltage. With a known magnetic fi eld, its distance from the Hall plate can be determined. Using groups of sensors, the rela-tive position of the magnet can be deduced.

Electricity carried through a conductor will pro-duce a magnetic fi eld that varies with current, and a Hall sensor can be used to measure the current with-out interrupting the circuit. Typically, the sensor is in-tegrated with a wound core or permanent magnet that surrounds the conductor to be measured.

Frequently, a Hall sensor is combined with cir-cuitry that allows the device to act in a digital (on/off) mode, and may be called a switch in this confi gura-tion. Commonly seen in industrial applications such as the pictured pneumatic cylinder, they are also used in consumer equipment; for example some computer printers use them to detect missing paper and open covers. When high reliability is required, they are used in keyboards. http://en.wikipedia.org/wiki/Hall_effect_sensor

A couple of availabe hall effect sensors are pic-tured at right.


DS1302 Timekeeping Chip

Real Time Clock Module

http:/

/www

.spar

kfun.c

omhtt

p://w

ww.pa

ralla

x.com


time

There are many chips and modules for keep-ing abolute time, also known as real time. A couple examples are pictured here.

The DS1302 trickle-charge timekeeping chip contains a real-time clock/calendar and 31 bytes of static RAM. It communicates with a microprocessor via a simple serial interface.

Only three wires are required to communicate with the clock/RAM: CE (chip enable), I/O (data line) and SCLK (serial clock). Data can be transfered to and from the clock/RAM 1 byte at a time, or in a burst of up to 31 bytes. The DS1302 is designed to operate on very low power, and retain the data and clock infor-mation on less than 1 μW.

This a custom designed module for the DS1307 Real Time Clock. The module comes fully assembled and pre-programmed with the current time (ok, so it’s our current time - MST). The included Lithium coin cell battery (CR1225 41mAh) will run the module for a minimum of 9 years (17 years typical) without external 5V power. The DS1307 is accessed via the I2C proto-col. We’ve written a test-bed to program the modules. This test-bed code should give you some insight on how to interface the module to any microcontroller us-ing our example software I2C and BCD routines.


Strait-Line Live Wire in Wall Sensor

Science Daily

http:/

/www

.amaz

on.co

m/Irw

in-60

4170

5CD-

Stra

it-Line

-Live

-Sen

sor/d

p/B0

002V

M7O4

http:/

/www

.scien

ceda

ily.co

m/im

ages

/2010

/09/10

0915

0942

30-la

rge.j

pg


live wire

Live wire sensors now come built into some higher end stud fi nders used in locating metal studs and the nails in wood studs. The live wire detectors help to locate the wiring embedded in the wall assem-bly so that you don’t cut through it.

In order to attach such a device to arduino, one may need to hack the commercial product.

This is an interesting article about using the wiring in one’s home as an atenna for powering low energy consuming sensors in the house to detect air quality, etc. http://www.sciencedaily.com/releas-es/2010/09/100915094230.htm


sensing the imperceptible

Documents