Touch alarm system schematic design
Use any suitable relay for the project and if you are not tight on area, use any size. I’ve develop this specific circuit to prevent students from fiddling using the security cameras in pc labs in the University I’m employed. I made certain the metal casing was not grounded. But as the schematic shows you can essentially hook it as much as any type of metal surface. I utilized a 12-vdc power adapter. Use any appropriate relay to handle your requirements. A ‘RESET’ switch (Usually Closed) can be added between the constructive and the ‘arrow-with-the-+’. The trigger (touch) wire is connected to pin 2 of the 555 and will trigger the relay, utilizing the body resistance, when touched. It is apparent that the ‘touching’ component has to be clean and can make good get in touch with with the trigger wire. This particular circuit may not be suitable for all applications. Just in case you wonder why pin 5 isn’t listed within the schematic diagram; it isn’t truly required. In certain noisy conditions a little ceramic capacitor is placed in between pin 5 and ground. It does no harm to add one or leave it out.
Go to that page to read the explanation about above circuit design.