Home security system construction using Laser beam

A low-cost, invisible laser circuit to protect your house from thieves or trespassers. A laser pointer torch, which is easily available in the market, can be used to operate this device

The block diagram of the unit shown depicts the overall arrangement for providing security to a house. A laser
torch powered by 3V power-supply is used  for generating a laser beam.
A combination of plain mirrors M1 through M6 is used to direct the laser beam around the house to form a net. The laser beam is directed to finally fall on an LDR that forms part of the receiver unit as shown in Fig.
Any interruption of the  beam by a thief/trespasser will result into energize the alarm. The 3V power-supply circuit is a conventional full wave rectifier-filter circuit. Any alarm unit that operates on 230V AC can be components. When switches S1 and S2 are activated, transformer X1, followed by a full-wave rectifier and smoothing capacitor C1, drives relay RL1 through the laser switch.
The laser beam should be aimed continuously on LDR. As long as the laser beam falls on LDR, transistor T1 remains forward biased and relay RL1 is thus in energized condition. When a person crosses the line of laser beam, relay RL1 turns off and transformer X2 gets energized to provide a parallel path across N/C contact and the pole of relay RL1.
In this condition, the laser beam will have no effect on LDR and the alarm will continue to operate as long as switch S2 is on.
When the torch is switched on, the pointed laser beam is reflected from a definite point/place on the periphery of the house. Making use of a set of properly oriented mirrors one can form an invisible net of laser rays as shown in the block diagram. The final ray should fall on LDR of the circuit.
Note. LDR should be kept in a long pipe to protect it from other sources of light, and its total distance from the source may be kept limited to 500 meters.
The total cost of the circuit, including the laser torch, is Rs 500/= or less.

How to assemble a Radio Control Electric Switch

This switch is quite simple but has some great features and worth a try. All of the parts are readily available from most electronics stores or if you tinker with electronics a bit you may have them in your junk box as odd spares.

How to make the printed circuit

Board as it is so easy and is a rewarding experience to complete the whole job yourself. There are no suggestions of how to mount the switch.
As you can see by the photo, didn't put it in a case as it would just add weight and  can't see why it would need it if you can have it held by foam rubber. I cut a cavity out of some foam and wrapped a rubber band around it all.
The relay is mounted away from the circuit so the motor current has less effect and cause glitches and mounted with double foam tape.T the relay away from the board to keep electrical interference to a minimum.
The circuit doesn't have to be made like this as you could have a go at building it up on a veroboard but I do find it a fair bit harder, somedon't. It is a bit bigger than it's commercial counterparts but this is as small as I think most people can go with an ordinary soldering iron and tools.
A 6v relay seems to work fine even though the receiver voltage is only 4.8v. There are no pads included on the P.C board for the switching side of the relay as it depends on what sort is used. Be sure to find one that can handle the current that is put through it and do a good job of the soldering as there is a lot of vibration in a model aircraft. A double pole relay can be wired to short out the motor when power isn't on so a folding prop can stop rotating and fold properly. See diagram. Adjust the trim pot so that the relay turns on at the desired position of the radio stick.

Note: there is a slight delay in switching.  You can get a receiver plug by buying a servo extension lead and cutting it to the desired length.

To make the Printed Circuit  Board

Things needed

Blank board copper on one side. (Fibreglass is preferable but the older bakalite type material is ok. It fractures easier though)
Dalo pen
Ferric chloride (You can get it already as a solution or as powder and mix it yourself. Read the warnings about it's corrosive properties as you may end up with no sink pipes.)
Carbon paper (The same sort of stuff that you get in receipt books etc.)

Draw out diagram by placing the carbon paper onto copper face and the master on top. Then fill in the tracks you've drawn onto the copper with the Dalo pen. Cut board to size & put in Ferric Chloride till excess copper is etched. You could warm up the ferric chloride to make it work a little quicker. Swish the solution around a bit to keep fresh solution up to the copper. Wash & clean up then drill holes. The holes are quite small and you may need to but that size drill at an electronics store as well. Centre punch the
holes first makes it easier to drill.

See the prototype

You may need to obtain a chart that shows how to orientate the transistors the right way. In the diagram there are markings for each leg as B,E,C which is base, emitter and collector. These have to be the right way round and as they vary on different transistors of the same sort you'll have to do some digging yourself or as the supplier of the parts.
The Integrated circuit the electrolytic capacitor and the diode are the other three parts that must go the right way. The IC usually has a notch or similar at the end that corresponds with pin one marked on the diagram.

The diode has a black band at one end and that also can be seen on the diagram. The capacitor usually has negative or positive marked on the case and you'll see the + marked on the board diagram.
The trim pot RV1 uses only the middle and one outside leg. Just bend the other out of the way.
To find the way to wire the receiver plug, look on your servo wires and see if there is a red, black and another color wire as it is probably red for positive, black for negative.

Layout and print details

CX-BK7 Aiwa DVD DECK RECEIVER How to assemble the mechanism

HOW TO INSTALL THE CAM (EJECT LOCK)

Rotate the cam (BU U/D) fully in the direction of arrow.
2 Engage the gear (eject lock) and the gear of the cam (eject lock) aligning the mark with the center of the gear (eject lock)

HOW TO INSTALL THE CAM (GEAR)

Check that the cam (BU U/D) can not be rotated in the direction of arrow.
2 Align the mark on the cam (gear) with the boss as shown in the figure and install the cam (gear).

HOW TO INSTALL THE GEAR (MODE 2)

1 Align the mark on the rotary encoder (S701) with the projection of the assy.

2 Check that the cam (BU U/D) can not be rotated in the direction of arrow.
3 Install the gear (mode 2

HOW TO INSTALL THE GEAR (MODE CAM)

1 Slide the shaft in the direction of arrow.
2 Align mark A on the gear (mode cam) with mark B on the slider (mode cam) assy, then install the gear (mode cam).
3 Check that mark C on the gear (mode cam) is in alignment with mark D on the cam (gear).

HOW TO INSTALL THE ROTARY ENCODER (S702), GEAR (STOCKER COMMUNICATION), HOW TO INSTALL THE CAM (STOCKER U/D)

PHASE ADJUSTMENT BETWEEN PINIONS (SLIDER) AND SLIDER-1 TO 5 (L/R)

1 As shown in the following figure, adjust the portion A of each slider to the boss with the slider-1 to 5 (L) and the slider-1 to 5 (R) pushed in the arrow directions respectively (see Fig)

2 Paying attention to the up/down direction of the pinion (slider) (see Fig. 2), install each pinion (slider) so that the portion B of each pinion (slider) meshes with the portion A of each slider (see Fig. 3).
Note: Push in the pinion (slider) until the claw of the boss comes out above the pinion (slider) to lock.

How to disassemble the optical pick-up mechanism: OPTICAL PICK-UP SECTION (DVBU16V)

SW (1) BOARD, SW (2) BOARD, SW (3) BOARD, SW (4) BOARD, BRACKET (TOP) ASSY and RELAY BOARD

MOTOR (STOCKER) ASSY (STOCKER) (M761): MOTOR (ROLLER) ASSY (ROLLER) (M781): MOTOR (MODE) ASSY (MODE) (M771)

TIMING BELT (FRONT/REAR):  CAM (GEAR):  SENSOR BOARD