Welcome to Ron J's Circuit Pages

Two-Zone Burglar Alarm
This two-zone alarm has automatic exit, entry and siren cut-off timers. It was developed for the Beginner's Guide To Cmos Timers. So it has a particularly detailed circuit description. There's an optional One-Time-Only module. It will force the siren to switch off after the first ten minutes - and prevent the alarm from activating a second time.

An Expandable Multi-Zone Modular Burglar Alarm
This circuit features automatic Exit and Entry delays and a timed Bell Cut-off. It has provision for both normally-closed and normally-open contacts, and a 24-hour Personal Attack/Tamper zone. By using the Expansion Modules, you can add as many zones as you require; some or all of which may be the inertia (shock) sensor type.

A One-Time-Only Burglar Alarm
When this alarm is activated its Siren will sound once - for up to 20-minutes. Then it will switch off and remain off. The basic circuit has a single zone with independently adjustable Exit and Entry delays. This will be adequate in many situations. However, there's also a range of Expansion Modules. These will allow you to add any number of Instant Zones, Tamper Zones and Personal Attack Zones to your system.

An Expandable 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. The basic alarm has a single zone. This will be adequate in many situations. However - the modular design means that you can add as many zones as you like to the system. Details of a Four-Zone expansion module are provided.


An Expandable Transistor Based Burglar Alarm
This transistor based alarm features automatic Exit and Entry delays - together with a timed Bell Cut-off and system Reset. Along with the Exit/Entry zone - the basic alarm board has one Instant Zone. This will be adequate in many situations. However - the modular design means that it's easy to add as many zones as you like to the system. Details of a Four-Zone expansion module are provided.

A Transistor Based Single Zone Alarm
The circuit features automatic Exit and Entry delays, timed Bell Cut-off and System Reset. It has provision for normally-open and normally-closed switches and will suit the usual input devices (Pressure Mats, Magnetic Reed contacts, Foil Tape, PIRs and Inertia Sensors).

A Cmos Based Single Zone Alarm
This circuit features automatic Exit/Entry delays, timed Bell Cut-off and System Reset. It has provision for normally-open and normally-closed switches and will accommodate the usual input devices (Pressure Mats, Magnetic Reed contacts, Foil Tape, PIRs and Inertia Sensors).

A Simpler Cmos Single Zone Alarm
This circuit features automatic Exit/Entry delays, timed Bell Cut-off and System Reset. It will accommodate the usual normally-closed input devices (Magnetic Reed contacts, Micro Switches, Foil Tape and PIRs). And - with a simple modification - a normally-open trigger may be added.

A Cmos 4060 Burglar Alarm
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 - such as magnetic reed contacts, foil tape, PIRs etc. But it's easy to add a normally-open trigger. When the alarm is activated - the siren will sound for a fixed length of time. Then it will switch off - and remain off. The alarm will not reactivate. The Circuit Description offers a good introduction to both the Cmos 4060 - and the SCR.

A Dozen Small Cmos Alarm Circuits
This is a selection of small self-contained alarm circuits. They have a very low standby current - and are ideal for battery operation. Some are triggered by normally-open and normally-closed switches. And some react to changes in light or temperature. Included with each is a free SiMetrix circuit simulation.

Four Small Transistor Alarm Circuits
This is a selection of simple self-contained transistor based alarm circuits - complete with photographs. They are designed around the Complementary Latch. All may be triggered by both normally-open and normally-closed switches. They have a very low standby current - and are ideal for battery operation.

A Simple Shop-Door Alarm
Attach this circuit to the door of an unattended shop or reception area - and the sound of the buzzer will tell you when you have a customer. Add a siren - and it becomes a simple intruder alarm. The page includes a free SiMetrix circuit simulation.

A Simple Fire-Door Alarm
This circuit will let you know when something that should be kept closed - has in fact been left open. If you attach it to say a Fire-Door - it will allow you to pass back and forth freely. It's only when the door is open for more than about 30-seconds - that the buzzer will sound the alarm. The page includes a free SiMetrix circuit simulation.

A Shed / Garage Alarm
This is a basic single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays - and an optional Siren Cut-Off timer. It has an extremely small standby current. This makes it ideal for battery-powered operation. Use it in your caravan, mobile home, lock-up, or anywhere mains power is not available.

An Enhanced Shed / Garage Alarm
This is an enhanced version of the simple Garage/Shed Alarm. The Entry and Exit delays have been increased to about 30-seconds - and I've added a timed Siren cut-off and automatic Reset. I've also replaced the LED with an entry Buzzer. These enhancements mean that the new version will have a much wider application.

A Battery-Powered One-Time-Only Burglar Alarm
This is a single zone alarm - with independently adjustable Exit, Entry and Siren Cut-Off timers. When the alarm is activated its Siren will sound once - for up to 20-minutes. Then it will switch off and remain off. If you wish - you can use a mains power supply. But the extremely low standby current makes battery power a realistic option.

A 4-Digit Alarm Control Keypad
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.

A 5-Digit Alarm Control Keypad
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 - will de-energize it.

A 4-Digit Keypad Controlled Switch
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 SPCO/SPDT relay - but you can use a multi-pole relay if you wish.

Keypad Controlled Switch No. 2
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 code is somewhat less secure. However, there should be lots of situations where it will still be adequate.

Keypad Circuit - With Parallel Code Entry
This is a universal four-digit keypad-operated switch - with a difference. Instead of entering the security code one number at a time - the four keypad buttons must be pressed simultaneously. Split the code between two separately located keypads - and two people will have to be present in order to operate the switch. Each person can have a different three-digit code.

Electronic Door Release
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 period. Use the relay contacts to power the release mechanism. The standby current is virtually zero - so battery power is a realistic option.

An Alarm Power Supply With Battery Back-up
This Power Supply is suitable for the Modular Burglar Alarm. However, it has other applications. It is designed to provide an output of 12-volts, with a current of up to 1-amp. In the event of mains failure, the back-up battery takes over automatically. When the mains is restored, the battery recharges.

A Current Limiting Bench Power Supply
This is a 1-amp variable-voltage PSU. It adjusts from about 3v to 24v: and has the added feature that you can limit the maximum output current. This is invaluable when (for example) you power-up a project for the first time or soak-test a piece of equipment.

An Add-On Current Limiter For Your PSU
This circuit allows you to set a limit on the maximum output current available from your PSU. It's very useful when you power-up a project for the first time - or carry out a soak-test. By setting an upper limit on the current available from your PSU - you can protect both your power supply - and any device connected to it. It offers a simple and cheap alternative to the Current Limiting Power Supply.

A Transformerless Power Supply
This circuit will supply up to about 20mA at 12 volts. It uses capacitive reactance instead of resistance - so it doesn't generate very much heat. The circuit was designed to provide a cheap, compact power supply for Cmos logic circuits that require only a few milliamps. The logic circuits were then used to control mains equipment, using an optically-isolated triac.

A Cmos Based Vehicle Anti-Theft Alarm
This car alarm circuit features Exit and Entry delays - an instant alarm zone - an optional intermittent siren output - and an automatic Reset. By adding external relays you can immobilize the vehicle and flash the lights.

Two Cmos Based Vehicle Anti-Hijack Alarms     (300k Zip File)
The first circuit is designed for the situation where a hijacker forces the driver from the vehicle. If a door is opened while the ignition is switched on - the circuit will trip. After a few minutes delay - when the thief is at a safe distance - the alarm will sound and the engine will fail. The second circuit is a modification of the first - offering enhanced protection in many more situations.

Vehicle Anti-Hijack Alarm No. 3
Like the first two Hijack Alarms - if a door is opened while the ignition is switched on - the circuit will trip. And after a few minutes delay - when the thief is at a safe distance - the Siren will sound. But this time the engine does not go on to fail automatically. Instead - it will continue to run until the thief turns off the ignition. Then the engine will not re-start.

A Transistor Based Motorcycle Alarm
This circuit features a timed output and automatic reset. It can be operated manually using a key-switch or a hidden switch. By adding an external relay, it will set itself automatically - and/or immobilize the machine - every time you turn-off the ignition. It's easily adapted for a 6-volt system - so it will protect your "Classic Bike". - Now With Free SiMetrix Circuit Simulation.

A 555 -Timer Based 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 wired to set itself automatically when you turn-off the ignition. By adding external relays you can immobilize the bike, flash the lights etc. Now With Free SiMetrix Circuit Simulation.

A Cmos Based 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 wired to set itself automatically when you turn-off the ignition. By adding external relays you can immobilize the bike, flash the lights etc. It's easily adapted for a 6-volt system - so it will protect your "Classic Bike". - Now With Free SiMetrix Circuit Simulation.

A Simple Transistor Based Motorcycle Alarm
This is an even simpler transistor based motorcycle alarm. The circuit features a timed output and automatic reset. It can be operated manually using a key-switch or a hidden switch. By adding an external relay, it will set itself automatically - and/or immobilize the machine - every time you turn-off the ignition. It's easily adapted for a 6-volt system - so it will protect your "Classic Bike". - Now With Free SiMetrix Circuit Simulation.

Two Simple Relay Based Motorcycle Alarms
These are two - easy to build - relay-based alarms. You can use them to protect your motorcycle - but they have many more applications. If you use relays with 6-volt coils - they'll protect your "Classic Bike". Both alarms are very small. The completed boards occupy about half a cubic-inch - 8 cc. The standby current is zero - so they won't drain your battery.

Motorcycle Alarm No.7
This is a simple transistor alarm - with a siren cut-off timer. While the thief continues to move the bike - and the normally-open trigger switch continues to open and close - the siren will continue to sound. Shortly after the bike stops moving - the siren switches off - and the alarm resets.

Motorcycle Alarm No.8
This transistor alarm has a siren cut-off timer - and an LED activation indicator. Shortly after the thief abandons the bike - the siren will switch off and the alarm will reset. If the LED is lighting when you return - you'll know there's been an activation while you were away.

One-Time-Only Motorcycle Alarm
This is a "one-time-only" alarm - with an LED activation indicator. If the bike is moved - the siren will sound for about a minute. Then it will switch off - and remain off. It won't activate a second time. It can't be activated again - until the next time the alarm is set.

Cmos 4017 Sequential Timer
This timer will provide a sequence of up to ten separate events. The length of each event is set independently. And the sequence will run a fixed number of times - or repeat continuously. The individual events within the sequence - can be made to repeat and/or overlap. The accompanying Support Material includes a detailed description of how the Cmos 4017 works.

Two Cmos Based 24-Hour Timers
A pair of multi-range timers offering periods of up to 24 hours and beyond. Both are essentially the same. The main difference is, that when the time runs out, Version 1 energizes the relay and Version 2 de-energizes it. The first uses less power while the timer is running; and the second uses less power after the timer stops. Pick the one that best suits your application.

A Regularly Repeating Interval Timer
This circuit has an adjustable output timer that will re-trigger at regular intervals. The output period can be anything from a fraction of a second to half-an-hour or more - and it can be made to recur at regular intervals of anything from seconds to days and beyond.

Repeating Interval Timer No.2
This is a simpler repeating timer circuit. It uses just one Cmos IC - wired as an asymmetric oscillator. The length of time the relay remains energized - and the length of time it remains de-energized - are set independently.

Repeating Timer No.3
This circuit is very similar to Repeating Interval Timer No.2 . However - the addition of a light dependent resistor means that the operation of this timer can be limited to the daylight hours. A variable resistor (preset) lets you choose the level of darkness at which the timer will cease to function.

Repeating Timer No.4
This circuit is the opposite of Repeating Timer No.3 . Its operation can be limited to the hours of darkness. Again - the variable resistor (preset) lets you choose the level of darkness at which the timer will begin to function.

Repeating Timer No.5
This circuit is a temperature controlled version of Repeating Timer No.3 . The light dependent resistor has been replaced by a temperature dependent resistor or thermistor. And a small preset potentiometer lets you choose the temperature above which the timer will operate.

Repeating Timer No.6
This circuit is the opposite of Repeating Timer No.5. It will only begin to operate if the temperature falls below the preset level. Again - the variable resistor (preset) lets you choose the temperature below which the timer will function.

Repeating Timer No.7
This timer is based on a simple Cmos 4001 Monostable Circuit. The length of the ON period - and the length of the OFF period - can be set independently. With the right value timing components - periods of up to an hour or more are available.

Repeating Timer No.8
This circuit has an adjustable output time of up to one-hour. And it can be set to repeat at intervals of up to 24-hours and beyond. It's a single IC version of my first - Cmos 4060 based - Repeating Timer.

Repeating Timer No.9
This circuit has two independently adjustable 24-hour timers. There's a relay-timer that will energize the relay for up to 24-hours. And there's a repeat-timer that will restart the relay-timer - at regular intervals of up to 24-hours. It's a more versatile version of my first Repeating Timer.

Three Fake Alarms
Flashing LEDs can be used to create the impression that an alarm has been fitted. Or they can be used in conjunction with a real alarm - to warn-off a potential thief. These three small circuits will flash anything from a single LED - up to 90 LEDs and beyond - with a variety of speeds and patterns.

Three Flashing LED Doorbells
These circuits combine a buzzer with one or more LED displays. When the push switch is operated - the buzzer will sound and the LEDs will flash. When the switch is released - the buzzer will stop - but the LEDs will go on flashing for another 30 seconds or so.

Electronic Toggle Switch No.1
This simple circuit will energize and de-energize a relay at the push of a button. Pushing the button once - will energize the relay. And pushing it a second time - will de-energize the relay. The accompanying Circuit Description offers a good introduction to the workings of the Cmos 4013.

Electronic Toggle Switch No.2
This is similar to the first circuit - but it is based on the Cmos 4017. Pushing the button once - will energize the relay. And pushing it a second time - will de-energize the relay. The accompanying Circuit Description offers a good introduction to the workings of the 4017.

Electronic Toggle Switch No.3
This circuit can be used as two entirely separate toggle switches - with each push button successively energizing and de-energizing its own relay. Or the two switches can be interlinked with diodes - to produce a number of different switching patterns. For example - they can be used to reverse the direction of DC motors.

Cell Phone Controlled Toggle Switch
When a brief (free) telephone call illuminates the screen of an old mobile phone - the light from the screen operates a simple Cmos 4017 based Toggle Switch. I used a single-pole relay in the prototype But you can use a multi-pole relay if it suits your application. The Support Material Includes A Full Circuit Simulation.

Two Light Controlled Relays
These two circuits use LDRs (Light Dependent Resistors). Circuit No.1 energizes the relay when the light rises above a preset level. Use it to switch things on at dawn. Circuit No.2 energizes the relay when the light falls below a preset level. Use it to switch things on at dusk.

Two Temperature Controlled Relays
These two circuits use Thermistors (Temperature Dependent Resistors). Circuit No.1 energizes the relay when the temperature rises above a preset level. Use it to switch things on when it gets hot. Circuit No.2 energizes the relay when the temperature falls below a preset level. Use it to switch things on when it gets cold.

Thermostat With Adjustable Hysteresis
This small thermostat allows you to select the size of its hysteresis. You can set both the temperature at which the relay will energize - and the temperature at which the relay will de-energize. The difference between these two temperatures is the hysteresis.

Constant Temperature Controller
This circuit is like a dimmer switch. As the temperature rises - the controller turns the heater down. At the point where the heat output exactly matches the heat loss - the temperature stabilizes. The controller maintains this stability by making one-hundred fine adjustments to the heater's output - every second.

An Infra-Red Remote Control Extender
This is a battery powered Infra-Red Link that will allow you to change channels on your Satellite Receiver and operate the controls on your VCR & DVD from anywhere in the house.

A Decimal to BCD Decoder
This is a keypad circuit that will convert the decimal value of any keypad switch - into its BCD equivalent.

How To Choose The Right Parts
My circuits use a very limited range of basic general purpose components. This is deliberate. The components were chosen because they're cheap - and widely available. But - if you can't find the right part - or you simply want to substitute something from your junk box - this will help you select a suitable alternative.

How To Identify A Relay's Pin Configuration
Relays are very versatile - but they're not magic. All they do is make and break sets of mechanical contacts. With careful observation - and a little logical thought this page will help you work out what's happening inside the case.

How To Identify A Transistor's Pin Configuration - And Polarity
This page will help you to find the polarity and pin configuration of any small bipolar transistor. There is an element of trial-and-error involved. But the task is not too daunting. There are only three leads - collector - base - and emitter.

How To Design Stripboard Layouts
This page has everything you'll need to copy my design technique. I use a programme called Inkscape. It's available free - for Windows, Linux and Mac. And I've included a couple of sample layouts - to help you get a feel for how it works.

Plan Your Breadboard Layout In Advance
I used to design my breadboard layouts "on the fly". I always ended up with a real mess. And it took me forever to find the (inevitable) mistakes. So I've adapted my Stripboard Design Technique - for the breadboard.

How To Make Wire Links
I make my links from telephone cable - the kind used indoors to wire phone sockets. When I make links for my breadboard - I leave the insulation on. And when I make stripboard links - I take the insulation off.

How To Convert Any Stripboard Layout - Into A PCB
The conversion can be carried out using the Paint programme. I've illustrated the process with my simple Door Alarm Circuit. But the technique can be applied to any stripboard layout - from any source.

Converting More Complex Layouts - To PCBs
Here I've used the more complex Car Alarm Circuit to illustrate the process. The technique is exactly the same. I simply wanted to show that it can be applied to larger stripboard layouts.

How To Make Your Own Stripboard
Stripboard is simply a matrix of small holes - joined together in rows - by narrow strips of copper. If you can make a printed circuit board - you can make a section of stripboard.

How To Cure False Alarms.
All burglar alarms - even professionally installed systems - give trouble sooner or later. This article describes a simple technique that will help you find the cause of your false alarms. It also includes some useful tips on routine maintenance. These will improve the future reliability of your alarm system.

An Introduction to the Cmos 4001
This is a beginner's guide to the Cmos 4001. It starts with a detailed look at the operation of the IC; and then considers its practical use in a small Battery-Powered Door-Alarm circuit.

An Introduction to the Cmos 4011
This is a beginner's guide to the Cmos 4011. It starts with a detailed look at the operation of the IC; and then considers its practical use in a small Battery-Powered Fire-Door Alarm circuit.

A Beginner's Guide To Cmos Timers
You can build simple, useful and reliable timers with a single Cmos inverter. This article will show you how it's done. Then we'll string four of these simple timers together - and create a practical Two-Zone Burglar Alarm. If you want to design your own Cmos circuits - this is a good place to start.

An Introduction to the Complementary Latch
This is a beginner's guide to the Complementary Latch. It starts with a detailed look at how the Latch operates - and then considers its practical use in a small Battery-Powered Transistor Alarm circuit.

How To Measure the Switching Voltage And Hysteresis Of A Cmos Gate
Manufacturing tolerances mean that the switching characteristics of Cmos ICs vary from one batch to the next. This page provides two small circuits that will allow you to measure the exact switching voltage of common Cmos inverters and non-inverters.

Predicting Thermistor Values At Different Temperatures
Manufacturing tolerances mean that using the published data to predict a thermistor's resistance - is a waste of time. What you need is reliable input data - derived directly from your own particular thermistor - and a spreadsheet to do the work.

How To Calculate The Temperature Constant (Beta) Of A Thermistor
The spreadsheet used to Predict Thermistor Values required an expression for βeta. It was derived from the formula for R₂ published in the data sheets. This page explains how the formula for R₂ becomes a formula for βeta.