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Alarms and security circuit diagrams
August 3, 2010
This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Pressing a single key will energize the relay. Entering the Four-Digit code of your choice will de-energize it. [more]
August 3, 2010
This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Entering the First Four Digits of your chosen Five-Digit code - will energize the relay. Entering the Full Five-Digit code -... [more]
August 3, 2010
If you use a lamp with a motion sensor for outdoor lighting, the original electrical switch is actually no longer necessary. If you replace the switch with the circuit described here, an acoustical signal will... [more]
circuit from:http://www.extremecircuits.net/2010/05/bell-alarm.html
August 3, 2010
Protect your valuable laptop against theft using this miniature alarm generator. Fixed in-side the laptop case, it will sound a loud alarm when someone tries to take the laptop. This highly sensitive circuit uses a... [more]
circuit from:http://www.extremecircuits.net/2010/05/laptop-protector.html
August 3, 2010
This circuit, enclosed in a small plastic box, can be placed into a bag or handbag. A small magnet is placed close to the reed switch and connected to the hand or the clothes of... [more]
circuit from:http://www.extremecircuits.net/2009/07/mini-alarm.html
August 3, 2010
A complementary transistor pair (Q2 & Q3) is wired as a high efficiency oscillator, directly driving the loudspeaker. Q1 ensures a full charge of C2 when power is applied to the circuit. Pressing on P1,... [more]
circuit from:http://www.extremecircuits.net/2009/07/powerful-security-siren.html
August 3, 2010
This alarm circuit was designed to monitor a mains-powered smoke detector located in a shed (which is used to house dog kennels). It provides complete isolation from the mains so that low-voltage (12V) cabling could... [more]
circuit from:http://www.extremecircuits.net/2010/05/remote-alarm-for-smoke-detector.html
August 3, 2010
This is a Universal version of the Four-Digit Alarm Control Keypad. I have modified the design to free up the relay contacts. This allows the circuit to operate as a general-purpose switch. I've used a... [more]
August 3, 2010
This is a simplified version of the 4-Digit Keypad Controlled Switch. I have modified the design to reduce the complexity of the circuit - and the number of components required. As a result - the... [more]
August 3, 2010
This circuit is designed to operate an electrical door-release mechanism - but it will have other applications. When you enter the four-digit code of your choice - the relay will energize for a preset time... [more]
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