This tutorial covers the low cost DHT temperature & humidity sensors. These sensors are very basic and slow, but are great for hobbyists who want to do some basic data logging. The DHT sensors are made of two parts, a capacitive humidity sensor and a thermistor. There is also a very basic chip inside that does some analog to digital conversion and spits out a digital signal with the temperature and humidity. The digital signal is fairly easy to read using any microcontroller.
NEW PRODUCT – DHT22 temperature-humidity sensor + extras. The DHT22 is a basic, low-cost digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin (no analog input pins needed). Its fairly simple to use, but requires careful timing to grab data. The only real downside of this sensor is you can only get new data from it once every 2 seconds, so when using our library, sensor readings can be up to 2 seconds old.
Simply connect the first pin on the left to 3-5V power, the second pin to your data input pin and the right most pin to ground. Although it uses a single-wire to send data it is not Dallas One Wire compatible! If you want multiple sensors, each one must have its own data pin! We have written an Arduino library with example code
Compared to the DHT11, this sensor is more precise, more accurate and works in a bigger range of temperature/humidity, but its larger and more expensive
Comes with a 10K resistor, which you will want to use as a pullup from the data pin to VCC.
NEW PRODUCT – DHT11 basic temperature-humidity sensor + extras. The DHT11 is a basic, ultra low-cost digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin (no analog input pins needed). Its fairly simple to use, but requires careful timing to grab data. The only real downside of this sensor is you can only get new data from it once every 2 seconds, so when using our library, sensor readings can be up to 2 seconds old.
We have written an Arduino library with example code
Compared to the DHT22, this sensor is less precise, less accurate and works in a smaller range of temperature/humidity, but its smaller and less expensive
Comes with a 10K resistor, which you will want to use as a pullup from the data pin to VCC.
NEW PRODUCT – Waterproof DS18B20 Digital temperature sensor + extras. This is a pre-wired and waterproofed version of the DS18B20 sensor. Handy for when you need to measure something far away, or in wet conditions. While the sensor is good up to 125°C the cable is jacketed in PVC so we suggest keeping it under 100°C. Because they are digital, you don’t get any signal degradation even over long distances! These 1-wire digital temperature sensors are fairly precise (±0.5°C over much of the range) and can give up to 12 bits of precision from the onboard digital-to-analog converter. They work great with any microcontroller using a single digital pin, and you can even connect multiple ones to the same pin, each one has a unique 64-bit ID burned in at the factory to differentiate them. Usable with 3.0-5.0V systems.
NEW PRODUCT – Magnetic contact switch (door sensor). This sensor is essentially a reed switch, encased in an ABS plastic shell. Normally the reed is ‘open’ (no connection between the two wires). The other half is a magnet. When the magnet is less than 13mm (0.5″) away, the reed switch closes. They’re often used to detect when a door or drawer is open, which is why they have mounting tabs and screws. But these also have a sticky-foam-tape back so you can also place them in locations you cant attach with screws.
DS18B20 Digital temperature sensor + extras. These 1-wire digital temperature sensors are fairly precise (±0.5°C over much of the range) and can give up to 12 bits of precision from the onboard digital-to-analog converter. They work great with any microcontroller using a single digital pin, and you can even connect multiple ones to the same pin, each one has a unique 64-bit ID burned in at the factory to differentiate them. Usable with 3.0-5.0V systems.
The only downside is they use the Dallas 1-Wire protocol, which is somewhat complex, and requires a bunch of code to parse out the communication. If you want something really simple, and you have an analog input pin, the TMP36 is trivial to get going.
We toss in a 4.7k resistor, which is required as a pullup from the DATA to VCC line when using the sensor. We don’t have a detailed tutorial up yet but you can get started by using the Dallas Temperature Control Arduino library which requires also the OneWire Library.
These are often used for air conditioners, water lines, and other places where they can get damp. The PVC coating of the wires is good up to 105 °C so this isn’t good for very hot stuff.
We even toss in an additional 1% 10K resistor which you can use as calibration or for a resistor divider.
NEW PRODUCT – Wii controller (Nunchuck / Wiichuck). This is a generic Wii Nunchuck controller, we haven’t tried it with a Wii but it does work great with the Video Game shield, and all the microcontroller code we tried. There’s a 3-axis accelerometer inside as well as a resistive 2-axis joystick and two buttons. You can grab the data over two i2c data lines. There’s tons of example code for all sorts of microcontrollers for these guys!
To make the maze I used a box of MDF 25cm x 25cm and lid of another box in MDF 20cm x 20cm, which was mounted to the maze itself with bits and pieces of a handle sticks “giant” (5mm in diameter), a abandoned toy from my 3-year-old daughter. Four pieces of plywood served to make the middle frame. In this framework has been set the first servo axis that has stuck in the middle of one side of the cover 20×20 and is responsible for movement in the Y axis. The second servo, which is responsible for movement in X axis, is attached to the larger box and has its axis stuck on one side of the intermediate frame so as to be perpendicular to the first servo.
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The code, which can be seen below, was adapted from code found on this site: http://www.windmeadow.com/node/42
I replaced the piece of code that prints the values on the screen for control of the servos. To improve the stability of the code make an average of the last 20 readings, adjust the scale and apply the results to the servos.
NEW PRODUCT – Touch screen (Nintendo DSL digitizer). Want to poke at your projects? This resistive touch screen can be used with a stylus or fingertip and is easy to use with a microcontroller. You can put it over a paper overlay for a touch control panel or attach it to an LCD to DIY a touch-activated display.
2.2″ x 2.75″ (55mm x 70mm) overall dimensions, 1.5mm thick
3.2″ diagonal active area, 80mm
600 ohms across X pins, 300 ohms across Y pins
4 wire resistive display, on a 0.5mm FPC connector
Use any microcontroller with 2 digital pins and two analog input pins
UPDATED PRODUCT! Medium 6V 2W Solar panel 2.0 Watt. These panels come to us from Voltaic Systems, makers of fine solar-powered bags and packs. These are waterproof, scratch resistant, and UV resistant. They use a high efficiency monocrystalline cell. They output 6V at 330 mA via 3.5mm x 1.3mm DC jack connector. The substrate is an aluminum / plastic composite, specifically designed to be strong and lightweight. They can easily stand up to typical outdoor use including being dropped and leaned on. They’re very high quality and suggested for projects that will be exposed to the outdoors.
New! These now comes with 4 plastic mounting screws which makes it easy to attach the panel, even to fabric!
IR detectors are little microchips with a photocell that are tuned to listen to infrared light. They are almost always used for remote control detection – every TV and DVD player has one of these in the front to listen for the IR signal from the clicker. Inside the remote control is a matching IR LED, which emits IR pulses to tell the TV to turn on, off or change channels. IR light is not visible to the human eye, which means it takes a little more work to test a setup.
There are a few difference between these and say a CdS Photocells:
IR detectors are specially filtered for Infrared light, they are not good at detecting visible light. On the other hand, photocells are good at detecting yellow/green visible light, not good at IR light
IR detectors have a demodulator inside that looks for modulated IR at 38 KHz. Just shining an IR LED wont be detected, it has to be PWM blinking at 38KHz. Photocells do not have any sort of demodulator and can detect any frequency (including DC) within the response speed of the photocell (which is about 1KHz)
IR detectors are digital out – either they detect 38KHz IR signal and output low (0V) or they do not detect any and output high (5V). Photocells act like resistors, the resistance changes depending on how much light they are exposed to
NEW PRODUCT – PIR motion sensor with cable! This is now back in stock and comes with a cable! PIR sensors are used to detect motion from pets/humanoids from about 20 feet away (possibly works on zombies, not guaranteed). This one has an adjustable delay before firing and we include a 1 foot (30 cm) cable with a socket so you can easily reposition the sensor or mount it using the two drills on either side. Runs on 3.3-6V. Digital signal output is high/low. For a full tutorial with wiring diagrams, code examples and project ideas, PIR sensor tutorial page!
We needed a datalogger that provided a timestamp, and that would last 2 weeks in the woods. Using a laptop would require a generator or humongous battery. This Instructable shows how to make a datalogger from an Arduino and datalogger shield connected to a TelosB wireless sensor board and a battery that is large, but not wheelbarrow large. Your data goes onto a SD memory card on the datalogger for pickup later (whenever you have to change the batteries on all the wireless radios in your network, for example). The main challenge is getting the serial signal out of the TelosB before it gets translated into USB. We could probably have reprogrammed the TelosB to output the serial on another pin, but why program when you can solder?
You can get going quickly – saving data to files on any FAT16 or FAT32 formatted SD card, to be read by any plotting, spreadsheet or analysis program. We even have a tutorial on how to use two free software programs to plot your data The included Real Time Clock timestamps all your data with the current time, so that you know precisely what happened when!
Please note that this item does not come with an Arduino (you’ll need one to use with the shield), or an SD card. It does come with the RTC battery, however. The kit is un-assembled, You’ll need some basic soldering skills to put it together, but even if you don’t have much experience you can get it done in under 1 hour.
SD card interface works with FAT16 or FAT32 formatted cards. 3.3v level shifter circuitry prevents damage to your SD card
Real time clock (RTC) keeps the time going even when the Arduino is unplugged. The battery backup lasts for years
Included libraries and example code for both SD and RTC mean you can get going quickly
Prototyping area for soldering connectors, circuitry or sensors.
Onboard 3.3v regulator is both a reliable reference voltage and also reliably runs SD cards that require a lot of power to run
NEW PRODUCT – Thermocouple Type-K Glass Braid Insulated – K. 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 inexpensive thermocouples have a vinyl covering which can melt at around 200 degC, this one uses a fiberglass braid so it can be used in high temperature measurements such as heaters and ovens.
Printable catalog (PDF)
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