> For the complete documentation index, see [llms.txt](https://docs.idew.org/code-internet-of-things/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.idew.org/code-internet-of-things/references/physical-inputs/motion-sensor.md). # Motion Sensor The motion sensor included in your Photon kit uses passive infrared (PIR) light to detect movement in the surrounding environment up to about 10 feet away. ![Motion Sensor](/files/-LK2so6o7Oxf8dBU2fgG) ## How to Connect Motion Sensor The motion sensor has a 3-wire JST connector with 3 pins for plugging into a breadboard. (If the end of your connector doesn't have 3 metal pins, attach the [JST right angle connector](https://www.sparkfun.com/products/9750) included in your kit.) To connect a motion sensor to your Photon using the breadboard, you will need: * Motion sensor (with 3-pin JST right angle connector) * 3 jumper wires (use different colors to help identify them; it may help to match the sensor wires) | Motion Sensor | Photon Pin | | ------------------- | ----------------------- | | Black - Data | any I/O pin | | White - Ground | GND | | Red - Power (5-12V) | 5V through VIN or V-USB | {% hint style="success" %} **5V REQUIRED:** The motion sensor requires 5V of power to operate. * If your Photon is being powered through the **barrel jack**, connect to the **VIN** pin. * If your Photon is being powered through the **Micro-USB** port, connect to the **V-USB** pin. {% endhint %} Here are the steps to connect the motion sensor to your Photon using the breadboard: 1. Insert the 3 pins of the motion sensor connector into **different** terminal strip rows on the breadboard. (Different terminal strip rows have different row numbers.) 2. Plug one end of a **jumper wire** into the **same** terminal strip row as the **sensor's black wire**. Plug the other end of this jumper wire into an I/O pin on the Photon circuit board. 3. Plug one end of a **second jumper wire** into the **same** terminal strip row as the **sensor's white wire**. Plug the other end of this jumper wire into a pin hole connected to GND: either plug it into a negative power rail (which is connected to GND via a different jumper wire), or plug it directly into a GND pin on the Photon circuit board. 4. Plug one end of a **third jumper wire** into the **same** terminal strip row as the **sensor's red wire**. Plug the other end of this jumper wire into either the VIN pin or V-USB pin on the Photon circuit board (or to a **positive** power rail on the breadboard that is connected to VIN or V-USB). If your Photon is being powered through the barrel jack, connect to the VIN pin. Otherwise, if your Photon is being powered through the Micro-USB port, connect to the V-USB pin. Here's a wiring diagram showing a possible way to connect a motion sensor: ![](/files/-LK3-rTiigygDbv1sv-d) Keep in mind that your connection can look different than this example diagram: * Your motion sensor pins could be inserted into **different row numbers**. (The example connects the sensor pins to rows 16-18 on the left side of the breadboard.) * Your motion sensor pins could be inserted into a **different column** of the breadboard. (The example connects the sensor pins into column A of the terminal strip rows.) * Your sensor's black wire could connect (through a jumper wire) to a **different I/O pin**. (The example connects to the D0 pin.) * Your sensor's white wire could connect (through a jumper wire) to **either to a different GND pin or to a negative power rail connected to a GND pin**. (There are three available GND pins.) * Your sensor's red wire could connect (through a jumper wire) to **either the VIN pin or V-USB pin (or to a positive power rail that's connected to one of these pins).** (The example connects directly to the V-USB pin.) ## How to Code Motion Sensor The basic steps to use a motion sensor in your app code are: 1. Declare a global variable to store the I/O pin number for the motion sensor. 2. Set the pin mode for the motion sensor pin in the `setup()` function. 3. Use a `digitalRead()` statement to check whether the sensor detects any motion, and add code statements that should be performed if motion is detected (or not detected). ### Global Variable You should declare a global variable to store the I/O pin number that the motion sensor's data wire is connected to. This will make it easier to understand your code (and easier to modify the code if you were to connect the motion sensor to a different pin number). Add this code statement (modify if necessary) **before** the `setup()` function: ```cpp int motion = D0; ``` This line of code does 3 things (in order): 1. **It declares a data type for the variable's value.** In this case, `int` stands for integer (whole number). Photon pin numbers are always treated as `int` values (even though they have letters). 2. **It declares the variable's name.** In this example, the variable will be called `motion`. You can change the variable name, but choose a name that will make sense to anyone reading the code. 3. **It assigns a value to the variable.** In this example, the variable's value will be equal to `D0`. If necessary, modify this value to match the actual I/O pin number that your button is connected to. ### Set Pin Mode You need to set the pin mode for the motion sensor to be used as an input. Add this code statement (modify if necessary) **within** the `setup()` function: ```cpp pinMode(motion, INPUT_PULLUP); ``` The `pinMode()` method requires two parameters inside its parentheses (in this order): 1. **The I/O pin number**, which can be the actual pin number (such as: `D0`, etc.) or a variable that stores a pin number. In this example, a variable named `motion` is listed. If necessary, change this to match the variable name for your button. 2. **The mode value**, which will always be `INPUT_PULLUP` for a motion sensor. ### Check If Motion Detected The `digitalRead()` method is used to check whether the sensor currently detects any motion. Add this code (modify as necessary) to your app within the `loop()` function or a custom function: ```cpp int motionState = digitalRead(motion); if(motionState == LOW) { ​ // add code to do something if motion detected ​ delay(2000); // wait 2 seconds before checking sensor again } ``` In the first code statement, a local variable named `motionState` is declared that will have a data type of `int` (integer). This variable is made equal to whatever value is returned by the `digitalRead()` method. You can change the name of this variable, but it will make sense if it's similar to the variable name used for the motion sensor pin number. The `digitalRead()` method requires one parameter insides its parentheses: 1. **The I/O pin number**, which can be the actual pin number (such as: `D0`, etc.) or a variable that stores a pin number. In this example, the variable named `motion` is listed. If necessary, change this to match the variable name for your motion sensor's pin number. The `digitalRead()` method will return a value of either `HIGH` or `LOW` (which are treated as if they were `int` values): * `HIGH` indicates that motion is **NOT** currently detected. * `LOW` indicates that motion is currently detected. The condition listed inside the parentheses of the [if statement](http://www.wiring.org.co/reference/if_.html) checks whether the value of `motionState` is [equivalent](http://www.wiring.org.co/reference/equality.html) to `LOW`: * If this condition is **true**, the code within the curly braces of the `if` statement will be performed. You will need to add code statements within the curly braces that perform the actions you want. * If this condition is **false** (because the `motionState` is `HIGH`), the code within the curly braces will **NOT** be performed. Optionally, you can add an [else statement](http://www.wiring.org.co/reference/else.html) to perform a different set of code statements when motion is **not** detected. **IMPORTANT:** You will notice that a `delay()` of 2 seconds is included when motion is detected. This delay is needed to allow the motion sensor to capture a new "snapshot" of the environment before checking the sensor again. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.idew.org/code-internet-of-things/references/physical-inputs/motion-sensor.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.