Simple Two-Transistor Motorcycle Alarm
When one of the switches is closed - the base of Q1 is connected to ground through D1 & R2. This switches Q1 on - and it in turn switches Q2 on. Q2 connects the...
Build Your Own Motorcycle Alarm
This circuit features an intermittent siren output and automatic reset. It can be operated manually using a key-switch or a hidden switch; but it can also be wi...
Build Your Own Motorcycle Alarm
This circuit features an intermittent siren output and automatic reset. It can be operated manually using a key-switch or a hidden switch; but it can also be wi...
Motorcycle Alarm No.1 - Construction Guide
When one of the normally-open switches is closed - two things happen. Firstly - the negative side of the relay coil is connected to ground through D1. This caus...
Modular Burglar Alarm
The Basic Alarm Circuit has an automatic Exit/Entry Zone - an Instant Alarm Zone that will accept both normally-closed and normally-open triggering devices - an...
How To Build A Simple Keypad Switch With A Tamper Alarm
This circuit is designed to be used with the Universal Keypad Operated Switch. A few genuine mistakes - made during code entry - will not activate the device. B...
How To Build A Simple Alarm Control Keypad
Pressing a single key on the keypad - will energize the relay. Entering a four-digit code of your choice - will de-energize the relay. The circuit was designed ...
How To Build An Anti-Hijack Vehicle Alarm
Before fitting this or any other engine cut-out to your vehicle - carefully consider both the safety implications of its possible failure - and the legal conseq...
How To Build A Keypad-Operated Door-Lock Release
This circuit is designed to operate an electrical door-release mechanism - but it will have other applications. Enter the four-digit code of your choice - and t...
Simple Door Alarm Circuit
This is a simple - easy to build - multi-purpose alarm. Build it yourself using stripboard or veroboard and a few cheap off-the-shelf components. Fit it to a do...
How To Build A Burglar Alarm Using A Cmos 4060
This is a single zone alarm - with automatic exit, entry and siren cut-off timers. It will accommodate all the usual types of normally-closed input devices - su...
How To Build A Simple Code-Operated Switch
This is a simplified version of the Universal Keypad-Operated Switch. I have modified the design to reduce the complexity of the circuit - and the number of com...
Battery Powered One-Time-Only Alarm - Support Material
The Cmos 4001 has four - independent - two-input NOR gates. The four gates are divided into two pairs. Gates 1 & 2 are wired together to form a type of latching...
How To Build A Simple Car Alarm And Immobilizer
This circuit features automatic exit and entry delays - an optional instant alarm zone - an optional intermittent siren output - and an automatic reset. By addi...
Surveillance Transmitter Detector
My site contains a few low power transmitters of one type or another, but until now no receiver. This circuit can be used to "sweep" an area or room and will in...
Keypad-Operated Switch No.2
This is a simplified version of the Universal Keypad-Operated Switch. I have modified the design to reduce the complexity of the circuit - and the number of com...
Four-Digit Keypad-Operated Switch
This is a universal version of the Four-Digit Alarm Keypad. I`ve modified the design of the output section - to free up the relay contacts. This allows the circ...
Electronic Door Release
This circuit is designed to operate an electrical door-release mechanism - but it will have other applications. Enter the four-digit code of your choice - and t...
Electronic Doorbell with Counter
This circuit uses a synthesized sound chip from Holtek, the HT-2811. This reproduces the sound of a "ding-dong" chiming doorbell. Additionally, the circuit incl...
An SCR Based Burglar Alarm
This is a simple SCR based burglar alarm circuit. Its features include automatic Exit and Entry delays - together with a timed Bell cut-off and Reset. It`s desi...