Metal Detector DIY

                           Metal Detector D.I.Y schematic diagram

The heart of this DIY metal detector circuit is CS209A. The metal detector is build with one 100µH coil. CS209A has one oscillator which forms a LC circuit, the inductance of the coil will change when it is near metal objects.

LED 1 will light and the buzzer turns on when the coil is changing inductance. The setup is easy, VR1 is adjusted (away from any metal objects) so that LED 1 will light and the buzzer sounds on, and then VR1 will be trimmed until led and buzzer are off.

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METAL DETECTOR Circuit

                                    METAL DETECTOR Circuit

This circuit detects metal and also magnets. When a magnet is brought close to the 10mH choke, the output frequency changes. 

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Rain Alarm

                                      Rain Alarm

                       GIVES BEEP WHEN WATER IS IN CONTACT WITH THE WIRE

      Water is a conductor of electricity. When water is in contact with the probe then there is a flow of current which reaches to the base of Q1. Transistor Q1 is a NPN transistor which conducts. With the conduction of Q1 electron reaches to Q2 which is a PNP transistor .Q2 also conducts and current flows through the speaker. In a speaker there is inductive coil which causes motion in one direction and also produce induce current which is in opposite direction to the flow of current this induce current in the form of pulse flows through a capacitor, resistance and switches off Q1 and relax .this process repeats again and again till probe is in contact with water or we can say there is a oscillation in the circuit thus speaker diaphragm vibrates and gives a tone. Frequency of the circuit depends on the value of Speaker Coil impendence, Capacitor and Resistance Value.

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                 Traffic Light Project

This project operates red, amber and green LEDs in the correct sequence for a single UK traffic light. The time taken for the complete red - red & amber - green - amber sequence can be varied from about 7s to about 2½ minutes by adjusting the 1M preset. Some amber LEDs emit light that is almost red so you may prefer to use a yellow LED.

The 555 astable circuit provides clock pulses for the 4017 counter which has ten outputs (Q0 to Q9). Each output becomes high in turn as the clock pulses are received. Appropriate outputs are combined with diodes to supply the amber and green LEDs. The red LED is connected to the ÷10 output which is high for the first 5 counts (Q0-Q4 high), this saves using 5 diodes for red and simplifies the circuit.

Parts Required

• resistors: 470 ×3, 22k, 100k
• capacitors: 0.1µF, 1µF 16V radial, 10µF 16V radial
• diodes: 1N4148 ×6
• LEDs: red, amber (or yellow), green
• 1M preset, horizontal
• 555 timer IC, such as NE555
• 4017 counter IC
• DIL sockets for ICs: 8-pin, 16-pin
• on/off switch
• battery clip for 9V PP3
• stripboard: 20 rows × 21 holes

PCB LAY OUT :

CIRCUIT DIAGRAM :

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Light-sensitive Alarm

             Light-sensitive Alarm Project

The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens.
The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for
only a short time to prevent the battery running flat. Normal lighting can be used, but the circuit will work
best if a beam of light is arranged to fall on the light-sensor. Breaking this beam will then cause the
bleeper to sound. The light sensor is an LDR (light-dependant resistor), this has a low resistance in bright
light and a high resistance in dim light.
• The light-sensitivity of the circuit can be adjusted by varying the 100k preset.
• The length of bleep can be varied from 0.5 to 10 seconds using the 1M preset.
Using the 7555 low-power timer ensures that the circuit draws very little current (about 0.5mA) except
for the short times when the bleeper is sounding (this uses about 7mA). If the circuit is switched on
continuously an alkaline PP3 9V battery should last about a month, but for longer life (about 6 months)
you can use a pack of 6 AA alkaline batteries.


Parts Required

• resistors: 10k, 47k, 1M ×3 •  7555 low-power timer IC
• presets: 100k, 1M •  8-pin DIL socket for IC
• capacitors: 0.01µF, 0.1µF, 10µF 25V radial •  bleeper 9-12V
• transistor: BC108 (or equivalent) •  on/off switch
• LDR (light-dependant resistor) type ORP12 •  battery clip for 9V PP3

Stripboard Layout

Circuit diagram

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Dummy Alarm Project

                    Dummy Alarm Project

Parts Required

• resistors: 1k, 10k, 680k
• capacitor: 10µF radial
• LED: red super bright, 5mm diameter
• 7555 low power timer IC
• 8-pin DIL socket for IC
• battery clip
• 4.5V battery box for 3 AA cells
• strip board: 8 rows × 16 holes

This Dummy Alarm project makes an LED flash briefly once every 5 seconds to imitate the indicator light of a real alarm. The circuit is designed to use very little current to prolong battery life so that it can be left on permanently. An on/off switch is not included, but could be added if you wish.

The 7555 timer IC used is a low power version of the standard 555 timer. A 'superbright' red LED is used because this provides a bright flash with a low current. The LED is off for most of the time so the average total current for the circuit is less than 0.2mA. With this very low current a set of 3 alkaline AA cells should last for several months, maybe as long as a year.

The circuit will work with a standard 555 timer IC (such as the popular NE555) but this will increase the average current to about 2mA and the battery life will be much shorter. You can use a greater supply voltage (15V maximum) for this circuit but the 1k resistor for the LED should be increased to keep the LED current low at about 3mA. For example to use a 9V PP3 battery change the 1k resistor to 3k3. Note that AA cells will last longer than a 9V PP3 battery.

This project uses a 555 a stable circuit.

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Lie detector (Portable)

                  A Portable lie-detector

This is a portable lie-detector built in a tin box . maybe you could have some fun using this thing.

Note : this detector is less sensitive then a real one. this could be miss some (many) of the lies.

Things you'll need.

You will need some things below for this project.

1. circuit board
2. 10K resister
3. 47K resister
4. 470 resister
5. 1M resister x2
6. 47K VR
7. knob for VR
8. 2N3904 transistor x3
9. 0.1 ? mylar cap
10. slide switch.
11. 9V bettery snap
12. LED (one red, one green)
13. solding tools.
14. drill
15. basic tools,
16. velcro (magic strip)
17. aluminum foil
....and most of all, a tin box 

Make a finger pad

make a finger pads by sticking a aluminum foil to the velcro (strip)

And don' forget to stick a wire between the velcro and the foil!

Soldering the circuit

Solder the circuit as a diagram below. And before soldering the circuit, cut the circuit board to

suitable size to fit in the tin

Drilling the Tin case

Drill the tin for a VR.

and DO NOT use a sharp-end drill bit. it will tear the tin into half

Put the floor sheet

Put the floor sheet in a floor of the tin to avoid it from 'short circuiting'.

and secure it with a glue.

in my case, I used a piece of box, and secure with a hot melt

Put everything in order

Put everything in the tin and secure all of them with a glue, hot melt, etc 

Done

Now your lie detector is ready to go. first, put the finger pad to the finger of the 'suspect'
then, slowly, turn the VR until the 'true' LED is light, and the 'false' LED is dark.
then, ask a question to the suspect , when the false LED gets lighted, the suspect is lying

THANKS A LOT :)

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