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Worried about break-ins? You can get peace of mind by building your own video security system. You’ll need a spare VCR, a low-cost CCD video camera, one or two PIR sensors, an IR illuminator and this VCR Security Controller to operate the VCR. Design by BRANCO JUSTIC A Video Security System For Your Home W ITH PEOPLE’S RISING con- cern about break-ins and vandalism, video security systems are becoming very widespread. Now they are just starting to appear in upmarket homes although they are quite expensive and can cost thousands of dollars. However, there is no need to lay out lots of dollars if you want your own video security system. CCD video camera modules are becoming very small and quite cheap at around $150 or less so they can be the basis of an effective home video security system. The CCD camera featured in this article is quite tiny. Its PC board measures just 33mm square so it can be 62  Silicon Chip Fig.1: the VCR Security Controller is triggered into the recording mode when one of the PIR sensors detects motion. Note that the camera and the VCR are always on but the monitor does not have to be present. Fig.2: the circuit uses a 4093 to control two relays which are connected in parallel with the Record and Stop buttons on the VCR or its remote control. easily concealed. Nor is there any need for ugly spotlights in order for the camera to work. They can function in low ambient light and are sensitive to infrared which is invisible to human eyes. Therefore, you only need a relatively low power infrared LED illuminator for the system to work even in pitch darkness. The problem is that just having a camera outside your house and a video monitor inside is not much good if you’re not at home. If someone does something naughty on your property you need to be able to record it with a VCR. This is the sort of system which is routinely installed in shops and service stations. But the VCRs used in shops usually run 4-hour tapes at half speed so they can record an 8-hour stretch. One or two tapes can record a whole day’s trading. However, a system with a VCR running continuously is not practical for the homeowner. You have to remember to change tapes and that is not possible when you are away. So the system pre­sented here uses one or two passive infrared (PIR) sensors to monitor the camera’s field of view and then switch the VCR on for a fixed period if any motion is detected. Fig.1 shows the con­cept. The heart of the system is the VCR Security Controller board. This is hooked up to one or two PIR sensors and it con­trols two relays. The camera, IR illuminator, VCR controller and PIR sensors are continuously powered from a 12V DC plugpack and the VCR itself is switched on; ie, not on standby. The camera is connected to the video input on the VCR which can be connected to a standard TV or video monitor. Note that the video monitor does not need to be turned on at all, unless you want to check what has been recorded on the tape. The VCR controller has two relays and these are used to operate the Record and Stop functions on the VCR. The relays can either be used to operate the VCR directly, via connections across the Record and Stop buttons in the machine, or they can operate via connections across the Record & Stop buttons of the infrared remote control. Better still, if you have an old VCR with a wired remote control, it would be a simple matter to make connections via the remote control plug on the rear of the machine. Alternatively, if you don’t fancy modifying your existing remote control you could purchase a “learning remote control” and modify that instead. To be realistic though, you would probably want to dedicate one VCR to this security September 1997  63 Parts List 1 PC board, 103 x 52mm 2 relays with SPDT contacts 1 12V DC plugpack Fig.3: PIR sensors can have normally open or closed contacts or have a pull-down output involving a TTL stage or an open-collector transistor. Semiconductors 1 4093 quad NAND gate (IC1) 1 BC548 NPN transistor (Q1) 3 C8050 NPN transistors (Q2, Q3, Q5) 1 BC558 PNP transistor (Q4) 1 5.6V 400mW zener diode (ZD1) 5 1N4148 silicon diodes (D1, D2, D3, D4, D5) 2 G1G silicon diodes (D6, D7) 3 red light emitting diodes (LED1, LED2, LED4) 2 green light emitting diodes (LED3, LED5) Capacitors 3 22µF 25VW electrolytic 3 0.1µF monolithic 2 .015µF monolithic Fig.4: this is the component overlay for the PC board. Be aware that the C8050 transistors may be supplied in a different pinout from the EBC sequence that the board is designed for. application so it would not matter if it was internally modified or its remote control was modified. Each time one of the PIR sensors detects motion in the camera’s field of view it causes the “Record” relay in the VCR Security Controller to operate momentarily. This sets the VCR into record mode and it stays that way until the “Stop” relay on the VCR Security Controller operates momentarily. The time bet­ ween the record and stop signals will depend on how long the PIR sensors continue to detect motion and a delay period of about 60 seconds after motion. VCR controller circuit Fig.2 shows the circuit of the VCR Security Controller. It uses just one 4093 quad Schmitt NAND gate IC, five transistors, two relays and not much else. Transistor Q1 is turned on when one or both of the PIRs connected at the input senses motion. The input from Resistors (0.25W, 5%) 2 10MΩ 1 6.8kΩ 1 2.2MΩ 5 4.7kΩ 1 220kΩ 3 2.7kΩ 1 100kΩ 2 1.5kΩ 3 47kΩ 1 1kΩ the PIRs is coupled via diodes D1 & D2 and there are a number of options for connecting the PIRs to cope with devices that have normally open or normally closed outputs or TTL outputs. Fig.3 shows these options. When Q1 turns on it pulls pins 1 & 2 of IC1 low, causing pin 3 to go high. This quickly charges capacitor C3 via Resistor Colour Codes ❏ No. ❏  2 ❏  1 ❏  1 ❏  1 ❏  3 ❏  1 ❏  5 ❏  3 ❏  2 ❏  1 64  Silicon Chip Value 10MΩ 2.2MΩ 220kΩ 100kΩ 47kΩ 6.8kΩ 4.7kΩ 2.7kΩ 1.5kΩ 1kΩ 4-Band Code (1%) brown black blue brown red red green brown red red yellow brown brown black yellow brown yellow violet orange brown blue grey red brown yellow violet red brown red violet red brown brown green red brown brown black red brown 5-Band Code (1%) brown black black green brown red red black yellow brown red red black orange brown brown black black orange brown yellow violet black red brown blue grey black brown brown yellow violet black brown brown red violet black brown brown brown green black brown brown brown black black brown brown This picture shows the assembled VCR Security Controller board, together with the miniature CCD camera and an infrared illuminator board. The CCD camera measures just 33mm square and only need low-power IR illumination to work, even in pitch darkness. diode D3 and so pin 4 of IC1b goes low. This low signal is coupled via 0.1µF ca­pacitor C4 to pins 12 & 13 of gate IC1d and so pin 11 goes high for about a second to turn on NPN transistor Q3 and relay RLY1, the Record relay. Thus the VCR starts recording. When Q1 turns off, pin 3 goes low again but C3 can not discharge quickly via the now reverse-biased D3. C3 takes about a minute to discharge via resistors R6 & R7 and that causes pin 4 to go high again. This high signal is coupled via 0.1µF capacitor C5 to pins 8 & 9 of IC1c and so pin 10 goes briefly low to turn on PNP transistor Q4, NPN transistor Q5 and relay RLY2, the Stop relay. So the VCR stops recording. Five LEDs indicate the status of the VCR Security Con­troller board. LED1 turns on whenever the output of IC1a is high and so indicates when one of the PIRs is detecting motion. LED2 is on whenever relay RLY1 is actuated and indicates when the Record function is being selected. Similarly, LED3 is on when relay RLY2 is actuated and indicates when the Stop function is being selected. Both LED2 and LED3 will only turn on briefly. LED4 turns on while ever the output of IC1b is low and indicates that the VCR is in the recording mode. Finally, LED5 will always be on while the +5V rail is present. Transistor Q2 and zener diode ZD1 function as a 5V regula­tor, used in place of a conventional 3-terminal regulator as it takes less quiescent current. The quiescent current taken by the whole circuit is not much more than a milliamp since transis­tors Q1Q4 are normally off and IC1 is a CMOS IC which draws only a few mi­croamps. Assembling the PC board The components for the interface fit on a PC board measur­ing 103 x 52mm. An IR illuminator is necessary to complete the security system and two versions are shown here. The small one has 10 IR LEDs and will be quite suitable for close-up applications, while the larger 30-LED unit is necessary for covering larger open areas. September 1997  65 real trap for young players. The board is designed for transistors with the conventional EBC pinouts but check the transistors you have been supplied because they could have the ECB pinout se­quence. If so, you will have to bend the leads to make a correct installation. If you don’t fancy modifying your existing remote control you can purchase a “learning remote control” and modify that instead. Test procedure The assembly is quite straightforward – just follow the component layout of Fig.4. Fit the resistors first, followed by the capacitors, diodes and LEDs. Once this has been done, fit the transistors and the relays, followed by the IC. One point to watch when installing the transistors is to check the pinouts of Q2, Q3 & Q5. These are specified as C8050 gener­al purpose NPN transistors and their pinouts can vary – a Where To Buy A Kit Of Parts The PC board and other parts for this project are avail­able from Oatley Electronics, who own the design copyright. Their address is PO Box 89, Oatley, NSW 2223. Phone (02) 9584 3563; fax (02) 9584 3561. The prices are as follows: Video Controller board with all parts .....................................................$25 Used PIR sensors to suit .......................................................................$10 Small IR illuminator kit (with 10 880nm IR diodes) ................................$14 Large IR illuminator kit (with 30 880nm IR diodes) ...............................$30 CCD camera module ...........................................................................$120 12V DC plugpack to suit ........................................................................$10 Please add $5 to for postage and packing. 66  Silicon Chip Do not hook the PC board up to your VCR before you have done a bench test. To do this, connect the PC board to a 12V DC power supply. If you have PIR sensor, connect it to one of the inputs, using the correct hookup, as shown in Fig.3. Otherwise, simulate a trigger pulse by momentarily connecting either input to the free end of resistor R19 or R20. You should see LED1 light with each trigger pulse. LED4 should come on with the first trigger pulse and stay on for at least one minute after the last trigger pulse. LED2 will light momentarily when the PIR is initially triggered (activating the Record relay), while LED3 will light momentarily when the timing period has ended (activating the Stop relay). To avoid waiting a minute or more for the timer to complete its cycle, temporarily solder a link across R7 as shown in the circuit diagram. This reduces the timing cycle to a few seconds and makes testing easier. Troubleshooting should be easy, as the circuit is not com­plicated. If it doesn’t work as described, first check that you haven’t accidentally swapped any of the transistors or put them in the wrong way around – it is easy to do. Also, make sure all the diodes and electrolytic capacitors have been fitted with the right polarity. Connecting the remote control As already noted, the VCR Controller board can be connected across the Record and Stop buttons in your VCR. If you don’t mind accessing the internals of your VCR, that way is probably the most effective. Alternatively, you can connect the relays across the buttons in the remote control handpiece, or you can adapt a programmable IR remote control transmitter. If you intend to modify your remote control handpiece you will need to open the case and remove the batteries as a first step. Most IR remote controls are made in a similar way with PC tracks forming the switch contacts WARNING! THESE PREMISES ARE UNDER CONSTANT VIDEO SURVEILLANCE Fig.5: as a further deterrent to criminals and villains, make a copy of this notice and put it in your window. underneath each key in the keypad. All you need do is locate the tracks for the Record and Stops keys and connect the relay contact in parallel with the keys. When soldering wires across the tracks do NOT solder di­ rectly on the pads where the buttons make contact. If you do, you will probably render the Record and Stop buttons inoperative. This would be a tragedy, particularly if you were using a “learn­ing” as these buttons still have to be used to program the con­ trol. Better still, program the remote before you solder any wires to the back of the copper side of the board. Connecting the PIR sensors When connecting the PIR detector you need to identify the supply and output connections. You may need to unclip the case of the PIR to access the connections on its PC board. You may also need to operate the PIR on its own to identify whether its con­ tacts are normally open or normally closed or a “pull-down” output (ie, open-collector or TTL). That done, use the diagram of Fig.3 to make the PIR connections to the VCR Controller board. Now try the whole system running. When the PIR detects movement, LEDS 1, 4 & 2 should operate and recording should begin. LED4 will stay on for the duration of the timing period. When movement has ceased, LED3 will operate and recording should be stopped. Installing the system Because of the noise filtering in the input circuit of the VCR Controller, you can connect the PIR detectors with up to 30 metres of telephone cable. For best results the CCD camera should be connected with 75Ω coaxial cable. The cable length is not critical and can again be up to 30 metres or so, depending on the camera module. The IR light source is placed behind or alongside the camera so it lights the viewed area. The camera and the light source can be powered by the same 12V DC supply. Another facility you may want to add is a ‘time stamp’ on the VCR tape when recording. Some VCRs can be programmed to add the time and date when making a recording but most don’t have this feature. A simple way to achieve time stamping is with a talking alarm clock recorded onto the audio track of the VCR. Simply disconnect the speaker of the clock and connect the clock’s audio output to the VCR’s audio input socket. You might need a 100Ω load resistor in place of the speaker, to avoid latching up the amplifier output stage. The VCR should be well concealed and well away from the camera. Ideally, the camera should also be concealed but you might want to make a copy of the notice in Fig.5 and stick it to a window where potential thieves and vandals will see it. After all, it is better to discourage someone from committing a crime in the first place rather than getting evidence after the SC fact. September 1997  67