Build this DIY Intruder Alarm System using cheap off-the-shelf components. It has automatic Exit and Entry delays, a timed Bell Cut-off. Use it in your Home - Business Premises - Garage - Workshop - Shed etc. It has provision for normally-open and normally-closed switches and will accommodate the usual input devices (Pressure Mats, Magnetic-Reed contacts, Foil Tape, Movement Detectors and Inertia Sensors).

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Cmos Single-Zone Alarm - Support Material

Introduction

The prototype of the Cmos Single-Zone Alarm was built using only the Stripboard Layout as a guide. So - if you have faithfully reproduced that layout - you will have a working circuit.

Once you're satisfied that your layout is correct - and you have made a careful and thorough check of the underside of the board - it's time to power-up the circuit and test its operation. This is always an anxious moment. If you construct a lot of circuits - you might consider building the Current Limiting Power Supply - or alternatively - you could add the Simple Current Limiter to your existing PSU. Both will let you set an upper limit on the amount of current supplied to your circuit - and so protect it from any serious damage.

Setup

You can simulate the trigger-switches using short lengths of flexible multi-stranded wire - such as alarm cable. But if you want to check the sensitivity adjustment - you'll need to connect an inertia-sensor to the input terminals. A couple of LEDs and resistors are all that's needed to demonstrate that the Siren and Buzzer outputs are working properly.

Details of How to Prepare The
Cmos Single-Zone Alarm For Testing

Connect an LED in series with a 2k2 resistor to both the "Buzzer" and the "Siren" outputs. 

Connect two short lengths of wire to the normally-open input terminals. 

Strip the insulation from the ends of the wires - but do not allow the wire ends to touch each other.

Whether or not you're going to use inertia-sensors - begin by connecting two short lengths of wire to the normally-closed input terminals. 

Strip the insulation from the ends of the wires - and twist them together to simulate a normally-closed loop. 

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Next, connect the on/off switch - SW1. 

Pay particular attention to the position of the "Pole" connection. 

It doesn't matter which way round the other two connections are made. 

When you've done, place the switch in the "Off" position - and leave it there.

Turn R4 all the way to the left - its maximum value.

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Finally - connect the 12-volts DC to the input terminals. 

Pay particular attention to the polarity of the supply. 

Note that the positive connection goes to the top terminal.

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              Turn On The Power 

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At this stage the green LED should be lighting and the red LED should be off. 

While SW1 in the "Off" position - you can test the trigger circuit. 

Start by touching the ends of the blue wires together. 

The green LED should turn off. 

Separate the wires and it should turn on again. 

Repeat the test a few times. 

When you're satisfied that it's working properly separate the blue wires and move on to the normally-closed input.

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Open and close the red loop a few times. 

When you open the loop - the green LED should turn off. 

When you close the loop the green LED should turn on. 

When you're satisfied that it's working properly - twist the two red wires back together.

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Move SW1 to the "Set" position. 

The red LED should light. 

While the Exit Delay is running - touch the ends of the blue wires together. 

The green LED should turn off and the yellow LED - connected to the Buzzer output - should light. 

Separate the blue wires again. 

The yellow LED should turn off and the green LED should light. 

Repeat the test a few times during the first 10 seconds or so of the Exit Delay.

Then separate the wires and wait half a minute or so for the Exit Delay to end.

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When you're satisfied that the delay has finished - touch the wires together briefly.

This time the green LED should turn off and then on again - but the yellow LED connected to the Buzzer output should turn on and stay on. 

This means that the normally-open trigger has successfully activated the alarm. 

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Move SW1 to the "Off" position. 

The yellow LED should turn off. 

This means that SW1 has successfully de-activated the alarm.

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Next test the normally-closed input. 

Move SW1 to the "Set" position. 

The red LED should light. 

While the Exit Delay is running - open the red loop. 

The green LED should turn off - and the yellow LED connected to the Buzzer output should light. 

Close the red loop again. 

The yellow LED should turn off and the green LED should light. 

Repeat the test a few times during the first 10 seconds or so of the Exit Delay.

Then twist the red wires together and wait half-a-minute or so for the Exit Delay to end.

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When you're satisfied that the delay has finished - open the red loop briefly. 

This time the green LED should turn off and then on again - but the yellow LED connected to the Buzzer output should turn on and stay on. 

This means that the normally-closed trigger has successfully activated the alarm.

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Move SW1 to the "Off" position. 

The yellow LED and the red LED should both turn off.

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Next, - test the Entry Delay. 

Move SW1 to the "Set" position and wait for the Exit Delay to expire. 

Touch the ends of the two blue wires together briefly. 

The yellow LED attached to the Buzzer output should light and stay lit. 

If it goes out again then the Exit Delay hasn't expired. 

Wait a while and try again.

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The Entry Delay should last about 30 to 40 seconds. 

When it expires - the relay should energize and the yellow LED connected to the Siren output should light. 

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Make sure that the blue wires are not touching each other - and that the green LED is lighting. 

After about 15 to 20 minutes the relay should de-energize - both the yellow LEDs should turn off - and the alarm should reset. 

To check that it has reset properly - wait for the Exit Delay to expire and then trigger the alarm again. 

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When you're ready - move SW1 to the "Off" position. 

The red LED and both the yellow LEDs should turn off.

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If you're using an inertia-sensor - discard the red wire loop. 

Screw the sensor firmly to a solid surface - or clamp it in a vice. 

Then connect it to the normally-closed input terminals. 

Turn R4 all the way to the right - its most sensitive position. 

Move SW1 to the "Set" position - and wait for the Exit Delay to end.

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When you're satisfied that the exit delay has ended - tap the sensor with the handle of a screwdriver - or something similar. 

The Yellow LED connected to the Buzzer terminals should turn on and stay on - indicating that the tap on the sensor has triggered the alarm. 

Move SW1 to the "Off" position. 

The yellow LED and the red LED should both turn off.

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Repeat the test a number of times. 

Each time - turn R4 a little bit more to the left - then switch on and wait for the Exit Delay to expire. 

You should find that you need progressively harder blows to make the yellow LED light.

If at any time during the test your blow fails to activate the alarm then - before you tap the sensor again - wait a few seconds for C3 to discharge. 

This will give you the most accurate impression of the strength of blow needed for each setting of R4.

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You should also find that - as well as reacting to a single heavy blow - a series of gentler blows will also activate the alarm. 

Provided the delay between the blows is short - they will progressively charge C3 to the point where the circuit reacts. 

Thus, a low level - but sustained - attempt to force entry will also activate the alarm. 

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Finally, move SW1 to the "Off" position. 

The yellow LED and the red LED should both turn off.

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If You Find a Problem

If - in the course of the test - you find that something is not working properly, then a careful inspection of the relevant area of the circuit board should turn up the cause of the problem. If an LED is not lighting - check that it's connected the right way round. Where you've cut the board to size - look for small loose strands of copper left behind by the saw. Check the board for short-circuits caused by component leads touching each other. It can also happen that the stripboard itself is faulty. I have seen cases where the copper tracks have not been completely severed from one another during manufacture.

If you've built your circuit using the specified components - and you've followed the step-by-step construction guide described on the Cmos Single-Zone Alarm Support Page - then the chances are that any bug will be caused by something minor - a component connected the wrong way round - a missing or unwanted solder bridge - an incomplete cut in the track etc. If you haven't used the specified transistors - check the pin configuration. Just because the transistors look the same - do not assume that they have the same pin configuration.

If you can't see anything obvious then adopt a systematic approach to faultfinding. Simply replacing components at random is rarely successful. Begin by double-checking that all of the cuts in the tracks have been made - that they are all In The Right Place - and that they sever the track completely. Use a magnifying glass - and backlight the board. It only takes the smallest strand of copper to cause a problem.

When you're satisfied that the tracks have been severed in all the right places, check that you have made and correctly placed all 10 solder bridges - 11 if you've used the smaller preset. Mark each bridge with a felt-tip pen - or something similar - so that it can be easily identified later.

Next - carefully examine the full length of each track. Use a magnifying glass - and backlight the board. Look for unwanted solder bridges. Your felt-tip markings will tell you which ones should be there - and help you identify any that shouldn't be there.

If all else fails and you still haven't found the cause of the problem - work your way through the assembly instructions on the Support Page. Check each individual component and link - to make sure that it's present and correctly positioned.

Print out the drawings and mark off the components as you go. Pay particular attention to the orientation of the transistors, diodes and electrolytic capacitors. Take your time and examine each individual component carefully.

Click Here For A Photograph Of The Prototype.

Cmos Single-Zone Alarm Schematic	The Rest of Ron's Circuits	Write To Ron	More Free-to-Use Circuits	Circuit Exchange International

Cmos Single-Zone Alarm - Testing Your Circuit

Introduction

Setup

If You Find a Problem