How does timer know when to start

Question

The timer used here doesn't have a t=0 set time. How does it know when to start? Sorry if this is a silly question.

public partial class Form1 : Form

{
double t;
double dt = 0.1;
StreamWriter myfile = new StreamWriter("myresults.csv");
double previous_error = 0;
double integral = 0;
double error;
double setpoint = 0;
double measured_value;
double derivative;
double output;
double SpeedAccuracy = 0;
double Kp = 0.05, Ki = 0, Kd = 0;
double k1 = -2, k2 = 2;
private void timer1_Tick(object sender, EventArgs e)
{
if (car.speedX == 0) return;
*CODE BODY*
t = t + dt

Thanks in advance.

Nick

Ibrahim Ersoy · Answer

Hello Nick You need to set Timer's Enabled property to True to start timer1_Tick function. You can stop or start as long as you set its Enabled property to true or false. Anything particular you wish to know?

Nick Goodson · Answer

Hi thanks for that I have written the following code over the weeks as a student and now have to write a report on what/how it does what it does as a sort of manual for the reade. However I am still unsure as to how this timer works. Does it just loop around each time incrementing by 0.1seconds and updating all aspects within the loop? using System; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; using System.IO; using torcs; using System.Windows.Forms.DataVisualization.Charting; } namespace unmannedCar { public partial class Form1 : Form { double t; double dt = 0.1; StreamWriter myfile = new StreamWriter ( myresults.csv ); double previous_error = 0; double integral = 0; double error; double setpoint = 0; double measured_value; double derivative; double output; double SpeedAccuracy = 0; double Kp = 0.05 Ki = 0 Kd = 0; double k1 = -2 k2 = 2; private void timer1_Tick( object sender EventArgs e) { if ( car .speedX == 0) return ; measured_value = car .speedX; error = setpoint - measured_value; integral = integral + error * dt; derivative = (error - previous_error) / dt; output = Kp * error + Ki * integral + Kd * derivative; if (output > 1) output = 1; if (output output = 0; previous_error = error; setpoint = car .track[9] * 1.2; SpeedAccuracy = 0.9999 * SpeedAccuracy + 0.0001 * error; if (error > 0) { car .accel = output; car .brake = 0; } else if (error { car .accel = 0; car .brake = -output; } // turn the steering wheel car .steer = k1 * car .trackPos + k2 * car .angle; // Gear Change Up if ( car .rpm>=5000 & car .gear { car .gear = car .gear + 1; } // Gear Change Down if ( car .rpm car .gear>1) { car .gear = car .gear - 1; } // send the new controls to the car car .sendcontrols(); // display some results on screen label1.Text = car .speedX.ToString( 0000.00 ); label2.Text = car .accel.ToString( 0.0000 ); label3.Text = t.ToString( ##0.0 ); label4.Text = car .track[9].ToString( ##0.0 ); label5.Text = output.ToString( 0000.00 ); label6.Text = SpeedAccuracy.ToString( 0.000 ); label9.Text = car .distFromStart.ToString( 0.0 ); label11.Text = setpoint.ToString( 0.00 ); // save some results to a file so you can analyse them later in Excel myfile.WriteLine(t.ToString( 000.0 ) +  + setpoint.ToString( 0 ) +  + car .accel.ToString( 0.00 ) +  + car .rpm.ToString( 0000 ) +  + car .lastLapTime.ToString( 0000 ) ); myfile.Flush(); // plot the next points on the chart chart1.Series[ speedX ].Points.AddXY(t car .speedX); chart1.Series[ accel ].Points.AddXY(t car .accel * 5000); chart1.Series[ setpoint ].Points.AddXY(t setpoint); chart2.Series[ trackpos ].Points.AddXY(t car .trackPos); // update the timer t = t + dt; } public Form1() { InitializeComponent(); } private void Form1_Load( object sender EventArgs e) { // setup the chart axes chart1.Series[0].ChartType = SeriesChartType .Line; chart1.Series[0].Name = speedX ; chart1.Series.Add( accel ); chart1.Series.Add( setpoint ); chart1.Series[1].ChartType = SeriesChartType .Line; chart1.Series[2].ChartType = SeriesChartType .Line; chart1.ChartAreas[0].AxisX.Minimum = 0; chart1.ChartAreas[0].AxisX.Maximum = 20; chart1.ChartAreas[0].AxisX.Interval = 5; chart1.ChartAreas[0].AxisX.Title = secs ; chart1.ChartAreas[0].AxisY.Minimum = 0; chart1.ChartAreas[0].AxisY.Maximum = 100; chart1.ChartAreas[0].AxisY.Interval = 10; chart1.Titles.Add( stepresponse ); chart2.Series[0].ChartType = SeriesChartType .Line; chart2.Series[0].Name = trackpos ; chart2.ChartAreas[0].AxisX.Minimum = 0; chart2.ChartAreas[0].AxisX.Maximum = 20; chart2.ChartAreas[0].AxisX.Interval = 5; chart2.ChartAreas[0].AxisX.Title = secs ; chart2.ChartAreas[0].AxisY.Minimum = -1; chart2.ChartAreas[0].AxisY.Maximum = 1; chart2.ChartAreas[0].AxisY.Interval = 0.1; chart2.Titles.Add( stepresponse2 ); // connects to the Car comms .setupConnection( this ); // sets the loop time to 1000 milliseconds timer1.Interval = ( int )(dt * 1000); timer1.Enabled = true ; t = 0; myfile.WriteLine( t setpoint accel rpm Lap Time ); } private void button1_Click( object sender EventArgs e) { k1 = Convert .ToDouble(textBox1.Text); } private void label4_Click( object sender EventArgs e) { } }