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I have a LORA node up-linking data to a Thingspeak channel via The Things Network (TTN). Sometimes it stops sending data and I reboot it by logging into my console on TTN and sending a re-boot down-link message to the node. Is there any way I can transmit a downlink message to the node direct from Thinkspeak?
Hi may iknow why when i add widget gauge, the guage dont show the display
Hello MathWorks Community,
I am excited to announce that I am currently working on a book project centered around Matrix Algebra, specifically designed for MATLAB users. This book aims to cater to undergraduate students in engineering, where Matrix Algebra serves as a foundational element.
Matrix Algebra is not only pivotal in understanding complex engineering concepts but also in applying these principles effectively in various technological solutions. MATLAB, renowned for its powerful computational capabilities, is an excellent tool to explore and implement these concepts, making it a perfect companion for this book.
As I embark on this journey to create a resource that bridges theoretical matrix algebra with practical MATLAB applications, I am looking for one or two knowledgeable individuals who have a firm grasp of both subjects. If you have experience in teaching or applying matrix algebra in engineering contexts and are familiar with MATLAB, your contribution could be invaluable.
Collaborators will help in shaping the content to ensure it is educational, engaging, and technically robust, making complex concepts accessible and applicable for students.
If you are interested in contributing to this project or know someone who might be, please reach out to discuss how we can work together to make this book a valuable resource for engineering students.
Thank you and looking forward to your participation!
I created an ellipse visualizer in #MATLAB using App Designer! To read more about it, and how it ties to the recent total solar eclipse, check out my latest blog post:
Github Repo of the app (you can open it on MATLAB Online!):
Feature Request -- To add section highlighting to the editor, just like in 2021a!
What's the weather like in your place?
Hi guys
This is regarding my shared ThingSpeak channel. Previously it was showing the widgets side by side but in recent days it's showing widget under widget.
Why is that? Please help. 
#include <WiFiS3.h>
#define LDR_PIN A0 // LDR sensor pin
#define WIFI_SSID "Nahi Chalega"
#define WIFI_PASSWORD "12234556889"
#define THINGSPEAK_HOST "api.thingspeak.com"
#define THINGSPEAK_API_KEY "xxxxxxxxxxxxxxxx" // Replace YOUR_API_KEY with your ThingSpeak Write API key
#define CHANNEL_ID "2498369" // Replace YOUR_CHANNEL_ID with your ThingSpeak channel ID
WiFiSSLClient client;
void setup() {
Serial.begin(9600);
connectWiFi();
}
void loop() {
int ldrValue = analogRead(LDR_PIN); // Read LDR sensor value
Serial.print("LDR Sensor Value: ");
Serial.println(ldrValue);
sendToThingSpeak(ldrValue);
delay(2000); // Send data every 20 seconds
}
void connectWiFi() {
Serial.println("Connecting to WiFi");
WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("\nConnected to WiFi");
}
void sendToThingSpeak(int value) {
if (client.connect(THINGSPEAK_HOST, 80)) {
String data = "field1=" + String(value);
String request = "POST /update HTTP/1.1\nHost: " + String(THINGSPEAK_HOST) + "\nConnection: close\nX-THINGSPEAKAPIKEY: " + String(THINGSPEAK_API_KEY) + "\nContent-Type: application/x-www-form-urlencoded\nContent-Length: " + String(data.length()) + "\n\n" + data;
client.print(request);
Serial.println("Data sent to ThingSpeak!");
} else {
Serial.println("Failed to connect to ThingSpeak!");
}
client.stop();
}
I'm excited to share some valuable resources that I've found to be incredibly helpful for anyone looking to enhance their MATLAB skills. Whether you're just starting out, studying as a student, or are a seasoned professional, these guides and books offer a wealth of information to aid in your learning journey.
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I found this link posted on Reddit.
https://workhunty.com/job-blog/where-is-the-best-place-to-be-a-programmer/Matlab/
Hello Everyone,
I have modelled a FOC using average converter, and the PWM signal is generated using PWM generator (3-phase, 2-level). First, it had error of algebraic loop, but after searching in MATLAB community, I have used unit delay to avoid loop, but still when use local solver option is uncheked in the solver configuration, it still shows algerbaic loop, but when local solver is checked, it works. So, kindly put some light on this issue.
Rught now, the second issue which Im currently facing is " Index expression out of bounds. Attempted to access element 2. The valid range is 1-1." and "Function call failed.
Function 'PWM Generator (Three-phase, Two-level)/Switching Time Calculation' (#59.72.154), line 3, column 1:
"[TgabcON,TgabcOFF,ModWave] = ee.control.pwmSwitchingTimeTwoLevel(Vabc,vdc,fsw,PW"
Launch diagnostic "
I have attached the simulink model hereby. Kindly looking for your expert opinion on how to solve these issues.
Let S be the closed surface composed of the hemisphere 
and the base 
Let 
be the electric field defined by 
. Find the electric flux through S. (Hint: Divide S into two parts and calculate 
).
and the base Let be the electric field defined by . Find the electric flux through S. (Hint: Divide S into two parts and calculate ).% Define the limits of integration for the hemisphere S1
theta_lim = [-pi/2, pi/2];
phi_lim = [0, pi/2];
% Perform the double integration over the spherical surface of the hemisphere S1
% Define the electric flux function for the hemisphere S1
flux_function_S1 = @(theta, phi) 2 * sin(phi);
electric_flux_S1 = integral2(flux_function_S1, theta_lim(1), theta_lim(2), phi_lim(1), phi_lim(2));
% For the base of the hemisphere S2, the electric flux is 0 since the electric
% field has no z-component at the base
electric_flux_S2 = 0;
% Calculate the total electric flux through the closed surface S
total_electric_flux = electric_flux_S1 + electric_flux_S2;
% Display the flux calculations
disp(['Electric flux through the hemisphere S1: ', num2str(electric_flux_S1)]);
disp(['Electric flux through the base of the hemisphere S2: ', num2str(electric_flux_S2)]);
disp(['Total electric flux through the closed surface S: ', num2str(total_electric_flux)]);
% Parameters for the plot
radius = 1; % Radius of the hemisphere
% Create a meshgrid for theta and phi for the plot
[theta, phi] = meshgrid(linspace(theta_lim(1), theta_lim(2), 20), linspace(phi_lim(1), phi_lim(2), 20));
% Calculate Cartesian coordinates for the points on the hemisphere
x = radius * sin(phi) .* cos(theta);
y = radius * sin(phi) .* sin(theta);
z = radius * cos(phi);
% Define the electric field components
Ex = 2 * x;
Ey = 2 * y;
Ez = 2 * z;
% Plot the hemisphere
figure;
surf(x, y, z, 'FaceAlpha', 0.5, 'EdgeColor', 'none');
hold on;
% Plot the electric field vectors
quiver3(x, y, z, Ex, Ey, Ez, 'r');
% Plot the base of the hemisphere
[x_base, y_base] = meshgrid(linspace(-radius, radius, 20), linspace(-radius, radius, 20));
z_base = zeros(size(x_base));
surf(x_base, y_base, z_base, 'FaceColor', 'cyan', 'FaceAlpha', 0.3);
% Additional plot settings
colormap('cool');
axis equal;
grid on;
xlabel('X');
ylabel('Y');
zlabel('Z');
title('Hemisphere and Electric Field');
I feel like no one at UC San Diego knows this page, let alone this server, is still live. For the younger generation, this is what the whole internet used to look like :)
%%
clear
clc
close all
% TODO - Replace the [] with channel ID to write data to:
writeChannelID = 'your channel ID'; %channel ID
% TODO - Enter the Write API Key between the '' below:
writeAPIKey = 'your write API Key'; %write API Key
% url for POST request
url = 'https://aemo.com.au/';
webText = webread(url);
filteredData(4) = urlfilter(url,'<div class="summary-row-value">');
display(filteredData(4), 'AEMO');
thingSpeakWrite(writeChannelID, filteredData(4), 'WriteKey', writeAPIKey);
The cloks have changed in the UK having gone forward 1 hour but the times on the thingspeak graphs are out an hour - what is the solution please
Although, I think I will only get to see a partial eclipse (April 8th!) from where I am at in the U.S. I will always have MATLAB to make my own solar eclipse. Just as good as the real thing.
Code (found on the @MATLAB instagram)
a=716;
v=255;
X=linspace(-10,10,a);
[~,r]=cart2pol(X,X');
colormap(gray.*[1 .78 .3]);
[t,g]=cart2pol(X+2.6,X'+1.4);
image(rescale(-1*(2*sin(t*10)+60*g.^.2),0,v))
hold on
h=exp(-(r-3)).*abs(ifft2(r.^-1.8.*cos(7*rand(a))));
h(r<3)=0;
image(v*ones(a),'AlphaData',rescale(h,0,1))
camva(3.8)
I keep getting this error, what do I do?
Error: File: convert_mnist_to_mat.m Line: 63 Column: 1
This statement is not inside any function.
(It follows the END that terminates the definition of the function
"read_mnist_labels".)
function convert_mnist_to_mat(mnist_dir, output_file)
% Function to convert MNIST dataset files into .mat format
% Check if the directory exists
if ~isfolder(mnist_dir)
error('MNIST directory does not exist.');
end
% Read training images
train_images = read_mnist_images(fullfile(mnist_dir, 'train-images-idx3-ubyte'));
% Read training labels
train_labels = read_mnist_labels(fullfile(mnist_dir, 'train-labels-idx1-ubyte'));
% Read test images
test_images = read_mnist_images(fullfile(mnist_dir, 't10k-images-idx3-ubyte'));
% Read test labels
test_labels = read_mnist_labels(fullfile(mnist_dir, 't10k-labels-idx1-ubyte'));
% Save data into .mat file
save(output_file, 'train_images', 'train_labels', 'test_images', 'test_labels');
disp('MNIST dataset converted successfully.');
end
function images = read_mnist_images(filename)
% Function to read MNIST image data
fid = fopen(filename, 'rb');
assert(fid ~= -1, ['Could not open ', filename, '']);
magic_number = fread(fid, 1, 'int32', 0, 'ieee-be');
assert(magic_number == 2051, ['Invalid magic number in ', filename]);
num_images = fread(fid, 1, 'int32', 0, 'ieee-be');
num_rows = fread(fid, 1, 'int32', 0, 'ieee-be');
num_cols = fread(fid, 1, 'int32', 0, 'ieee-be');
images = fread(fid, [num_rows, num_cols, num_images], 'uint8');
fclose(fid);
images = permute(images, [2, 1, 3]); % Convert from (rows, cols, images) to (cols, rows, images)
end
function labels = read_mnist_labels(filename)
% Function to read MNIST label data
fid = fopen(filename, 'rb');
assert(fid ~= -1, ['Could not open ', filename, '']);
magic_number = fread(fid, 1, 'int32', 0, 'ieee-be');
assert(magic_number == 2049, ['Invalid magic number in ', filename]);
num_labels = fread(fid, 1, 'int32', 0, 'ieee-be');
labels = fread(fid, [num_labels, 1], 'uint8');
fclose(fid);
end
% Usage example:
mnist_dir = 'C:\Users\gabep\Desktop\MNIST';
output_file = 'mnist_dataset.mat';
convert_mnist_to_mat(mnist_dir, output_file);
One of the privileges of working at MathWorks is that I get to hang out with some really amazing people. Steve Eddins, of ‘Steve on Image Processing’ fame is one of those people. He recently announced his retirement and before his final day, I got the chance to interview him. See what he had to say over at The MATLAB Blog The Steve Eddins Interview: 30 years of MathWorking
Hi everyone, I need help for transfering the data from a ThingSpeak' channel to Google Sheets. Please help me.
Hello everyone.
I have modelled a three phase inverter to run a 5Kw PMSM motor (MATLAB preparametrized). The torque load is applied through ideal torque source and step junction, and the speed of the motor is visualized. When I provide the gate signal only through SPWM generator (No control, only SPWM signal generation through carrier and sine wave comparison),
- The speed stabilizes around 62 rad/sec after some initial oscillations, but when I try to run the same model using PMSM field oriented control block set, the speed is negative (negative rotation) and it keeps on increasing eventhough the speed reference provided is only upto 60. The waveform of both speed and torque has been attached hereby.
- Moreover, is there anyway to tune the PI controllers (inner and outer loops) of PMSM Field oriented blockset automatically.
- It can be seen from the torque waveform, there is soemkind of disturbance around 0.4-0.45 sec, which creates too much noise in current, torque waveforms. What could be the reason behind this.
Your help would be highly appreciated.
Thank you.
