Am2302 vs dht22

From my perspective these sensors are the same. The DHT11 on the other hand is a little cheaper but only intended for indoor use. The sensor is already calibrated by the manufacturer.

How to Use DHT-22 Sensor - Arduino Tutorial

It is almost plug and play. Unlike some temperature sensors, each of these temperature and humidity sensors requires its own data line.

So connecting several sensors on a single one-wire bus is not supported because the sensor does not have an address. In this how-to I will use 3. The sensor contains an 8 bit micro-controller. The sensor has an average power consumption of only 0. The low power consumption is achieved by going into sleep mode periodically.

A new sensor value can only be obtained every 2 seconds. See Datasheet. Wire the sensor as shown in the following picture. The first sensor pin is 3. The resistor is used as a pull-up resistor. Run sudo apt-get update and sudo apt-get upgrade -y to ensure your system is up to date. The temperature and humidity refers to a time of the day. For the data to be correct, your timezone must be set correctly.

When you execute date you should see the local time. If not, then you can set the correct timezone in sudo raspi-config. To install it, get the dependencies with sudo apt-get install -y build-essential python-dev git and then download and install the library with.

The first argument is the sensor type, it can be 11 or 22 or Actually the sensor can be queried from any Python script with just two lines of code. You can try this by starting Python interactive with sudo python then in the interactive mode type. To allow time-series analysis or visualization of the temperature and humidity, the values must be stored.My previously published results compared six AM a.

Here I repeat that experiment using the same apparatus and techniques but replace two of the sensors with alternative models, a DHT11 and a Sensirion SHT My conclusion was that in my experiments they did not, but they did deliver surprisingly good performance and very good value for money for most non-safety-critical, domestic DIY projects. The next obvious question is whether my tests would show a more expensive device to be better. Since I was re-running the experiment I also included the even cheaper and lower specification DHT The numbers in the following table appear on datasheets and are typically quoted by retailers.

The Sensirion datasheet on the other hand is detailed and comprehensive providing accuracy as a function of humidity as well as details of recommended calibration and linearization procedures. Note how Sensirion's absolute accuracy claims are less strict and more believable than those normally quoted for the DHT devices.

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Manufacturers' Specification. UPDATE: Since first writing this page a much improved data sheet has recently appeared which contains both clearer translations to English and more detailed specifications and plots. Accurately and repeatably measuring relative humidity is notoriously tricky. I am no expert in hygrometers.

I just devised the best experiment I could based on my reading of several papers on the topic and using a few items of household equipment I had lying around. Though five are mentioned, only four were under test at any one time. Sensor B failed during the experiment and was replaced by E. Apparatus setup is as previously described.

All sensors were powered from a 5V d. New software needed to be added to microcontroller to read the Sensirion device and was based on Markus Schatzl and Carl Jackson's Sensirion Arduino library. The reference calibration sources are still the same too, eleven saturated salt solutions and distilled water. Data were all collected in a similar manner to before with the sensors being allowed to stabilise for a few hours with each solution.

At more than ten times the price the SHT71 is unsuprisingly far superior to the others. It is both smaller and feels more solid. Note that the SHT71 has 1. I mounted mine in a 2. Figure 1. DHT11 looks similar to the AM Though somewhat smaller, it also has 0. The SHT71 has 0. The SHT71 consistently responded to changes the fastest, registering a change in a few seconds.The DHT11 and DH22 are both temperature and humidity sensors, but what's the difference between the two?

Let's go through the important differences, and how they may affect which one you choose for your next project. Both units use a capacitive humidity sensor and a thermistor to measure the surrounding air, and output a digital signal on the data pin no analog input pins neededto be easily read by a microcontroller. They are basic and slow, but great for small scale projects that require basic data logging. As you can see, the DHT11 has a much lower price point, but at the cost of range and accuracy.

Both sensors are easy to hook up, but collecting the data can require some careful timing. Both are also fairly sluggish, in that you can't query them more than once every second or two, so sensor readings can be up to 2 seconds old 1 second with the DHT If accuracy is important for your project, and you don't mind the higher price, go for the DHT Otherwise, the DHT11 should be good enough! Get started here! This site is best viewed in a modern browser with JavaScript enabled.

Here's a breakdown of the differences: As you can see, the DHT11 has a much lower price point, but at the cost of range and accuracy.Pages: [1]. The only sensor that is suited for your needs according to the datasheet, I never built a mushroom greenhouse is the BME the SI might work but has definitely the lower accuracy in the high humidity regions. Forget the DHT22, that's cheap crap, use it for the temperature but the measuring humidity more of a joke than serious work.

This is late information, but may be useful to others who come across this in a search. Here in the Houston, Tx area we often have long periods of very high humidity. Thus far all the DHT22's I have placed outdoors under a roof so they are not subject to rain or any direct moisture have begun giving false humidity readings after a day or two.

am2302 vs dht22

It appears this is a saturation problem and basically renders them useless for anything except air conditioned spaces. Caveat Emptor. I hope to turn the units into a robust open source platform for many different types of research.

So far all of the digital sensors have failed in more or less the same way: they work OK for a couple of weeks, then suffer from rising readings for a week or so till they hit their maximum and just stay pegged there from then on.

What I believe is happening is that the conditions go condensing, and then the moisture simply never evaporates again from inside the sensor material. After a few days "dry" the sensors return to normal operation. If you used higher bit depth temperature sensors you should be able to make this old school method work for your mushroom farm provided you can keep one of the sensors dry say inside a housing? I'll have to go digging, as many of those failures were from the time period.

Because they reset to apparently normal operation after being dried out. I'm not even sure this can be called a "failure" exactly. I tried several things and nothing worked. I have the same problem now. Could you any solution? Quote from: hectorgm on Dec 26,am. Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin.

In this tutorial you will learn how to use this sensor with Arduino uno. Did you use this instructable in your classroom? Add a Teacher Note to share how you incorporated it into your lesson. 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.

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Connections are simple, the first pin on the left to V power, the second pin to your data input pin and the right most pin to ground. Try downloading the codebender plugin and clicking on the "Run on Arduino" button to program your Arduino board with this sketch.

Below you will also find codebender serial monitor, press connect button to start receiving data from sensor. You have successfully completed one more Arduino "How to" tutorial and you learned how to use the DHT sensor.

Question 1 year ago on Step 2.

am2302 vs dht22

However if I use the online uploader it indicates it up loaded successfully. I want to use this program with a LCD but if I can't compile this portion of the code I cannot add to it, any suggestions?

Reply 2 years ago. I connected everything perfectly, codes were also perfect but then i uploaded the code onto the Intel Galileo Gen2 board and found out that no humidity and temperature is measured perfectly through serial monitor. Please help me out. As long as ur furnace has some sort of electric starting and stopping mechanism electric heating system.

Otherwise you will have to think of a handy mech to turn on and off the furnace mechanically and electrically. Very thorough! Just want to mention that the DC is actually between 3. More by the author:. About: Arduino Tutorials by Codebender. So, let's get started! Add Teacher Note. Technical details: Power: V Max Current: 2. The connections are pretty easy, see the image above with the breadboard circuit schematic.

Here's the code, embedded using codebender!I will not repeat the detailed descriptions of the apparatus and methods that are given there and in Test and Calibrate DHT22 Hygrometers. I recently received some very friendly and helpful feedback from an engineer at Sensirion who told me that the one problem I experienced with my Sensirion SHT71 was characteristic of a contaminated sensor.

Looking at my previous tests e. The device performed admirably in all aspects except for this one systematic error trend. Polymer-based capacitive humidity sensors work by measuring the changing capacitance of the polymer material as it is permeated by varying levels of water vapour. It is obvious that if something other than water vapour manages to enter and gets retained within the sensor then the resulting output value will be wrong.

This risk of contamination has always been a common issue for all capacitance hygrometers and is one of the reasons they are great for low-cost devices, but typically not used as laboratory-grade reference sensors. However what I learnt from the engineer at Sensirion is that the tilt I see is the typical symptom for a device that has been contaminated by volatile organic compounds VOCs.

am2302 vs dht22

They typically have a lower dielectric constant than water and systematically tilt the calibration in the manner seen. The hypothesis is therefore that I have been testing a device that had somehow been contaminated right from the start.

My SHT71 has been very stable and repeatable for more than three years operation, but always had that calibration tilt. The good point here is that the tilt has not greatly changed with time, so it always was calibratable and being a linear tilt it only ever needed a two-point calibration to adequately measure and correct. The complicated multi-point calibration I performed here was never necessary. All the various manufacturers specify a procedure for restoring a contaminated sensor. This generally amounts to 'baking' the sensor in a dry atmosphere to drive off the contamination and then reconditioning for a period of time in a warm and relatively benign moist atmosphere.

I had not previously attempted this because of lack of confidence in maintaining the baking temperature for such a long period. With my other tests complete, I now decided there was nothing to lose if I destroyed the sensor and it was worth trying. My aparatus was extremely crude. Sealing the can is maybe not ideal since I am constraining any contaminant that does get driven off to just get reabsorbed. Also, the thermal regulation of my oven is unlikely to be particularly good.

Despite these many shortcomings, my interest was really just to see i if the device survived at all and ii if its calibration changed. The test method uses a variety of saturated aqueous solutions and the aparatus has all been previously described. One limitation here is that my aparatus relies on a heater for thermal regulation. Without any active cooling, the lower temperature limit is set by the ambient temperature in my garage.


The devices included are: Aosong AM A. These are the same two devices as have been in all previous test runs. They are two of the three remaining functioning devices from my original set of six. In terms of performance they were by coincidence the best and the worst of the six. Sensirion SHT The same device as has appeared in multiple previous tests but has now been through the bake and reconditioning process.

This is the device we want to see whether it has changed. Does not have the PTFE protective membrane. Silicon Labs Si Includes the PTFE protective membrane.

Bosch Sensortec BMEI am experimenting the WebGL 3D surface renders on this page and have had problems with very slow page loads in some browsers. Here I have added five new devices meaning this test now covers most commonly available low-cost digital hygrometers. This page will present only new results.

How DHT11 DHT22 Sensors Work & Interface With Arduino

For details of how the experiment works, please refer to the previous write-ups. The devices now included are: Aosong AM A. The DHT11 is clearly a different class of sensor with substantially lower specification and has been dropped from further investigation. Figure 1. Comparison of the packaging of the various devices. The devices on the lower row are all shown mounted on third party break-out boards that make it easy to interface the surface mount device to 2. The sensor itself is the small square component in the top right of each board.

The right hand device without the white protective cover is an HTU21D. The membrane obscures the manufacturer's mark on the left hand device, but reading the internal serial number shows it to be an Si Also commonly known as DHT Device E was selected as the best of the six I originally started with.

The AM is effectively the latest version of the AM with the addition of an option to communicate over I2C interface. It is physically a little smaller, but with identical pin-out. The one-wire serial of the AM is retained making this a simple drop-in replacement. The AM appears to be the same but in a much smaller physical package and narrower pin pitch. It might be electrically identical. There is some suggestion from the manufacturer's web site that this might already be discontinued and replaced by AM I am not sure.

The same device as was used in previous tests. I discuss these together though they are distinct devices from two different manufacturers. In normal use they are interchangeable both in terms of specification and communications protocols and even have the same I2C address so are drop-in replacements for each other.

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Similarly the Sensirion SHT21 not included here also has a near identical specification and interface. I have seen the same third party generic break-out boards being sold with any one of these devices attached.

See Figure 1. The one difference I have found and possibly the only way to be sure which device you have is in the devices' unique serial numbers for which each manufacturer uses a slightly different format, detailed in their respective datasheets.

So long as you do not attempt to read the device serial number, these three sensors function identically. That is not to say they will all perform identically.

Though equivalent for most normal use, the precise specification details do differ, most particularly in their speed of response. For this test I am running one device each, with and without. The intent had been to include an identical pair of sensors with and without the cover, however when my devices arrived I found the retailer had sent me HTU21s without the cover and Sis with the cover.

It was only by reading the internal serial numbers I was able to ascertain that. Though not discussed in detail on this page, the effect of using the protective cover on the response speed has been investigated elsewhere.

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