Put the stuff before setup() together, fix any duplicates:
int mamank=13; <<< pin assignment? If yes, this can be byte
int red=2; <<< pin assignment? If yes, this can be byte
int green=3; <<< pin assignment? If yes, this can be byte
int blue=4; <<< pin assignment? If yes, this can be byte
Put the stuff in setup() ...
You may try to implement some kind of ultrasonic transponders. The
emitter sends a code addressing a specific receiver. Upon recognizing
its address, the receiver replies after a short, fixed delay. The
emitter measures the time it took the response to reach it, and from
there computes the distance.
You may need some kind of omnidirectional transducers (e.g....
The vertices of two (wooden) triangles already constrains the problem - in a positive way - since the inter-point distances of each triangle's vertices is constant. If they were 6 individual, free-floating points, the job would be that much more complex -- 30 unknown distances (each point to each other point), instead of only 18 (each vertex to each of 3 ...
As @Majenko commented, the A0 input has a fixed voltage divider (see NodeMCU Schematics) that connects the A0 input to a 220kOhm resistor, then to the ADC pin of the ESP8266, then to ground via a 100kOhm resistor.
This effectively fixes the resistor values that can be used to scale the input of the NodeMCU. For a 0-5.0V input range (with sufficiently low ...
The low end of the values is limited by how much current your sensor can provide. If you use 1Ω and 2Ω resistors in series then your sensor will need to provide 1.67A to create 5V across the divider. I doubt that your sensor can do that. For most sensors, you would want to use resistors in the kilohm or tens of kilohm range.
The high end is ...
Can you make Arduino Uno send information through a WiFi module to a server?
Yes, I can.
The simplest way is through an HTTP "GET" request. Every time you request a web page (and there are plenty of examples of that) you are sending data to the server to tell it both what web page to get (/foo/bar.php) and what data to submit to that web page (?baz=4).
Since all of these cheap fingerprint readers are similar you can find a compatible datasheet and just find the commands and descriptions there. However, I couldn't find a datasheet that would include a good description of the protocol. So the other option is to look at the protocot through the software SFGDemo which is apparently capable of getting an image ...
Most PIR sensors provide a simple relay output. That means they are nothing more than a switch as far as the Arduino is concerned.
You can connect hundreds of switches to an Arduino. With judicious use of diodes and a matrix arrangement you can hundreds with not many IO pins. For example an 8x8 matrix of switches gives you 64 PIR sensors with just 16 IO ...
This article claims the the DHT22, a slightly upgraded version of the DHT11, is able to handle wires of up to 30M when powered with 5V. I don't think power is the issue, as much as the ability of the signal line to carry the signal over that length of wire. Just use a 5V Arduino board and you should be ok. (It looks like each one only needs about 1.5 mA, so ...
DHT11 sensor uses a "single-Wire" protocol with open drain IOs. so it's fine for cable to be long. use a lower value Pull-up resistor for Data line of DHT11. the datasheet says a 5K pull-up resistor is enough for up to 20m wire length.
the process of reading a sensor can't be paralleled. you have to read them one at a time, store them on a local variable and ...
Both the tone() command and the PulseSensor_Playground library use Timer 0's interrupt. That means there are two implementations of the ISR for that interrupt. However you can only have one implementation of a function or ISR, so it conflicts.
You will have to modify the PulseSensor_Playground library to use a different timer. There may be a way in the ...
Your drawing is different from the drawing in the wiring diagram of that sensor: the resistor has to be connected right like the "4-20mA"-block in the drawing, (-) goes to ground. Measure the voltage directly at pin 2.
When reading the sensor's analog signal you can probably leave pin 4 floating.
I've seen so much fake projects from "Viral science". I'm not sure whether he/she simply don't know what he/she does or if he/she simply tries to trap people. This project is a race condition itself ;-).
Besides your battery is empty. I don't think it is a big problem to use a 9V block battery, but Gerben is right, it won't do its job for very long. Have ...
First this should be like this:
float* values= mq2.read(false); //false
and then write this to be printed in the serial monitor