Author Archives: marc

Portable slow whoop alarm for training purposes

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Used slow whoop alarms can be recycled into a portable version by adding a switch, a battery and a project box.

This portable version is useful during emergency response training. Persons attending the training can get used to the slow whoop sound and recognizing the alarm when used in real hazard situations.

The slow whoop alarm used in this schematic needs 12V or 24V to work. A simple PP3 9V block battery also works perfect, even when the battery is nearly empty there is still some sound. This slow whoop alarm needs about 10mAh of current, this means that the portable version can be used for 50 hours continuously. When using it for 30 seconds each training, this device can be used for 6000 training sessions. However, the battery will probably die from age before all the energy is used.

Windows Forms And Threading Is Easy

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Ever wanted to use threads and update the user interface without worry about the InvokeRequired thing? Use SynchronizationContext!

1 using System;
2 using System.Windows.Forms;
3 using System.Threading;
4
5 namespace WindowsFormAndThreadingIsEasy
6 {
7     public partial class Form1 : Form
8     {
9         private SynchronizationContext context;
10         private Thread myThread;
11         private event EventHandler myEvent;
12
13         public Form1()
14         {
15             InitializeComponent();
16
17             context = SynchronizationContext.Current;
18
19             myEvent += new EventHandler(Form1_myEvent);
20
21             myThread = new Thread(ThreadProc);
22             myThread.IsBackground = true;
23             myThread.Start();
24         }
25
26         private int i = 0;
27         void Form1_myEvent(object sender, EventArgs e)
28         {
29             i++;
30             textBox1.Text = i.ToString();
31         }
32
33         private void OnMyEvent(object state)
34         {
35             EventArgs e = state as EventArgs;
36             if (myEvent != null)
37                 myEvent(this, e);
38         }
39
40
41         private void ThreadProc()
42         {
43             while (true)
44             {
45                 Thread.Sleep(1000);
46
47                 if (context != null)
48                 {
49                     context.Post(new SendOrPostCallback(OnMyEvent), null);
50                 }
51                 else
52                 {
53                     OnMyEvent(null);
54                 }
55             }
56         }
57
58
59     }
60 }

Download Visual Studio 2005 Project. (unzip with 7-zip).