Light alarm Mmovement Detector

LIGHT ALARM - 3 (MOVEMENT DETECTOR)
This circuit is very sensitive and can be placed in a room to detect the movement of a person up to 2 metres from the unit.
The circuit is basically a high-gain amplifier (made up of the first three transistors) that is turned on by the LDR or photo Darlington transistor. The  third transistor charges the 100u via a diode and this delivers turn-on voltage for the oscillator.  The LDR has equal sensitivity to the photo transistor in this circuit.

signal by-pass

signal by-pass
This circuit allows a class-A amplifier to drive a low impedance speaker and has a low quiescent current. The 220R in series with the speaker limits the "wasted" current to about 20mA max as the transistor is generally biased at mid-voltage. However the transistor will be almost directly driving the speaker when a signal is being processed and the only limitation is the ability of the 220R to discharge the 100u during each cycle.
The circuit is called a signal by-pass as the signal by-passes the 220R and drives the speaker directly (via the 100u). 

5v Regulated Solar Power Supply Circuit

 5v SOLAR POWER SUPPLY 

This project uses the 1.2v rechargeable battery and solar panel from a Solar Garden Light.
unfortunately it cannot be used to generate a voltage higher than about 4v, so a new design had to be created. The circuit we have designed is shown above and provides a regulated 5v output @ 10mA. If a higher current is drawn, the output voltage will drop. At 15mA, the output voltage drops to 4v.
This supply has been specially designed for a microcontroller project, but it will also work for circuits such as amplifiers, FM transmitters etc.

HOW THE CIRCUIT WORKS
The circuit consists of an oscillator transistor and a regulator transistor.
The solar panel charges the battery when sunlight is bright enough to produce a voltage above 1.9v. A diode is required between the panel and the battery as it leaks about 1mA from the battery when it is not illuminated.
The regulator transistor is designed to limit the output voltage to 5v. This voltage will be maintained over the capability of the circuit, which is about 10mA.
The oscillator transistor must be a high-current type as is is turned on for a very short period of time to saturate the core of the transformer.
This energy is then released as a high-voltage pulse.
These pulses are then passed to the electrolytic and appear as a 5v supply with a capability of about 10mA. If the current is increased to 15mA, the voltage drops to about 4v.
The transformer is wired so that it gives POSITIVE feedback.
The transistor turns on via the 1k resistor and this produces expanding flux in the core.
The flux cuts the turns of the secondary winding and produces a voltage that ADDS to the turn on voltage and the transistor is turned on MORE. The transistor gets fully turned ON and the current through the primary becomes a maximum. The core becomes saturated and although the flux is a maximum, it is not expanding flux and thus the secondary produces no voltage (only the voltage and current supplied by the battery).
The voltage and current into the base of the transistor is reduced and this reduces the current through the primary.
The flux now begins to collapse and this produces a voltage in the secondary of an opposite polarity.
This turns the transistor OFF and the magnetic flux collapses quickly and produces a high voltage.
This voltage is passed through the diode and charges the electrolytic.
The circuit operates at approx 50kHz and the pulses quickly charge the electrolytic.
The 15k resistor has a 3k3 "trimmer" resistor to enable you to adjust the output to exactly 5v or slightly above 5v. Microcontrollers will work up to 5.5v but some will freeze at 5.6v, so be careful.
The output voltage is monitored at the join of the 15k resistor (and 3k3) and the 2k2 resistor. The voltage at this point is exactly 0.63v (630mV) and at this voltage the regulator transistor turns ON and robs the oscillator transistor with "turn-on" voltage.
When a load is placed on the output of the circuit, the voltage across the electrolytic drops and the regulator turns off slightly. This allows the oscillator transistor to operate "harder" and send pulses of energy to the electrolytic to charge it. If the load is removed, the current consumption for the circuit is about 3.5mA. This is the quiescent current for the circuit.
The output current is limited as each mA requires about 5mA from the battery.
At 15mA output, the current required from the battery is about 75mA. That's why we need a high-current capability transistor for the oscillator. A BC 547 transistor will not work, as it is not capable of passing a high current.
The solar panel will deliver about 10 - 15mA on bright sunlight, so any load on the output must be as small as possible.
An example is data logging, where the micro is active for short periods of time, then goes into "sleep" mode.

AUTOMATIC
The circuit can be made automatic by adding a 1k resistor and diode:

 

Automatic Solar Power Supply Circuit

The oscillator will turn off when the output from the solar panel is above 1.3v and although the circuit does not shut down to zero current, it consumes about 3 mA, while the shut-off circuit takes about 1mA.
On a bright day, the solar panel delivers 20mA to the battery, so the overall net charging current is about 15mA max. 
This means any data logging circuit or transmitter connected to the supply will only work at night.
To go over the purpose of the automatic section again:
The automatic components turn off the 5v section so the battery can charge and store enough energy to operate a transmitter during the night hours, when it will be needed.

If a very small current is required by a load such as a microcontroller, the following components can be used to bias the oscillator - as outlined by contributor James Moxham:

Low Current Power Supply Circuit

ASSEMBLY
The only component that has to be made is the fly-back transformer.
The core of a 10mH choke is used and re-wound with two windings.  Remove the fine winding and keep for another project.
The core is now bare and ready.
The first winding is 35 turns and the ends are connected to the pins at the end of the core. The other winding is 20 turns and has flying leads connected to two holes on the PC board. The 20 turn winding must be connected around a special way to provide a positive voltage to the base of the oscillator transistor. The operation of the circuit will depend on the direction of one winding relative to the other.
Rather than remember which way each winding has been wound, we simply connect the 20-turn winding to the board, via the flying leads, and if the circuit does not oscillate, we swap them over.
The diameter of the wire used for the transformer has been worked out so that it completely fills the bobbin. This gives the maximum milliwatt output.  That's why the old fine wire cannot be used.
Mount the components on the small PC board that comes with the kit or on a piece of matrix board.
Two switches have been used in the circuit to allow you to charge the battery while keeping the project off.

IF IT DOESN'T WORK
If the circuit does not work, the first thing to do is reverse the flying leads of the transformer.
If this does not solve the problem measure the current taken by the circuit. If it is HIGH, you have a failed (jammed) oscillator section or the output of the circuit may be shorted. If the consumption is LOW, the oscillator transistor may not be fitted correctly or the diode feeding the electrolytic may be around the wrong way.
Make sure the enamel is scraped off the ends of windings before soldering.
If the output voltage is above 5v, the regulator transistor is not working. Make sure the resistors are the correct value. Measure the voltage at the join of the resistors with a high impedance meter so no load is added to the circuit as this will upset the measurement.
If you have added the automatic section, make sure the solar panel is not receiving any sunlight as this will turn the circuit off.
5v Solar Power Supply
PARTS LIST

2 - 1k
1 - 2k2
1 - 3k3
1 - 15k
1 - 100u single ended electrolytic
2 - 1N 4148 signal diode
1 - 10mH choke (used for core)
2m - 0.25 mm winding wire
1 - BC 547 transistor
1 - BC 338 transistor
1 - mini slide switch

1 - 5v Solar Supply PC board
1 - Solar Garden Light (bought separately) 

source: www.talkingelectronics.com 

tags: Solar Power Supply

How to make a solar powered robot

Making your own solar powered robot is not as hard as you think. It is based on the Miller solar engine and has no digital electronics involved. But before we get started, it must be said that a robot is defined as "a mechanical intelligent agent which can perform tasks on its own". Note that the definition does not state that it has to be in a particular 'form'! So, though the robot we are going to build will look crappy, it will work and delight your heart. This project is more of a 'proof-of-concept' than the actual construction of an amazing robot! It we were to build an actual 'human-looking' robot, the difficulty level would catapult manifold. With that being stated, here we go:
Difficulty level:
'Moderately Challenging' - This DIY project involves building a basic circuit with a solar panel, capacitor, diode and transistor. The ability to make connections by reading a circuit diagram is absolutely essential though we try to simplify it in this tutorial. It would help if the 'builder' is familiar with the use of the soldering iron.
Time Required:
Once you have gathered all the essential components of the right specifications, it would take less than half an hour to make the circuit and have the robot up and running!
Resources required:
1. Two 3V 25mA solar panels
2. One 100 ohm resistor
3. One 3300uf capacitor
4. One 0.22uf capacitor. ( C1 in the diagram)
5. One 'signal' diode ( optional)
6. One small 2V motor
7. One 1381 part (CMOS voltage-controlled trigger - available at different limits) - Get one that matches the voltage across your motor (2V in this case)
8. A wire-wrap or breadboard
9. Soldering iron with solder
10. 2N3904 Transistor
Estimated cost:
The whole project will get done with your pocket money of a few dollars. The cost should not be a deciding factor for the project.
Instructions:
1. For those who know, just the circuit diagram should suffice. The only instruction would be, 'assemble your robot as per the diagram'.
2. Use the wire-wrap or breadboard to hold all the components.
3. Begin by connecting the transistor and the 100 ohm resistor.
4. The other end of the resistor is connected to the 'single' end of the 1381 part.
5. Connect the 0.22uf capacitor across the other two legs of the 1381 part.
6. Connect the two solar panels in parallel. Being in parallel, they will become a 3V, 50mA power supply.
7. Connect one terminal from the solar panels to one terminal of the motor.
8. The other terminal of the motor is connected to the 3300uf capacitor which is in turn connected to the other terminal of the solar panels. (The diagram shows 4700uf. Don't worry. As you will see later, the values can be altered to get different effects for the robot.)

Circuit Diagram
9. Complete the connections by hooking up the motor and diode with the setup as shown in the diagram.
10. Place the solar panels in the sun to see if you have got the connections right.
11. Once the correct connections are confirmed, take the components out, one by one, from the breadboard and start soldering them.
12. The motor can be placed between the legs of the big capacitor.
13. The bent legs of the small capacitor can double up as the legs of the robot.
14. Place the robot in the sun and watch it dance to the warmth. The dance will be intermittent with intervals of rest.
Frequently asked questions:
Ques: I am planning to make the robot for the first time. I have no previous experience in any of these electronic projects. Any tips for me?
Ans: This project will help you develop the confidence on many future electronic projects. Do not worry if you don't get it right the first time. The connections are simple but they may get confusing for the first timer. So make atleast two or three attempts before giving up. If you make those attempts, you surely will not have to give up is our belief.
Ques: What is the use of the diode in the whole setup? What are the specifications of the diode?
Ans: The diode can actually be discarded. The diode is actually added to prevent the battery discharge through the solar panel. Since we are not using a battery and the circuit does not need the capacitor to retain charge when the panel is not in the light, the diode becomes superfluous. But as we said, this is based on the Miller solar engine and so the circuit diagram shows the diode. If you are using one, any diode will do. The specifications are not important.
Ques: Can I find all the resources I need for constructing my robot, on the internet?
Ans: Of course! Try mouser.com or jameco.com or allelectronics.com. You can even do a simple Google search for BEAM hobby stores.
Quick Tips:
1. All the circuit components are small and so solder the connections starting in the middle and working your way out.
2. Vary the resistor and capacitors to find the optimum solution for your robot. This will alter the power going to the motor ( and hence the intensity of the robot movements) and the time interval between the movements. The solar energy is stored by charging the capacitor in circuit and when a threshold level is reached, the 1381 part gets triggered and works the motor.
3. Making a permanent circuit board will make it easy to test the different robots for their movement and interval between movements.
4. The values of the small capacitor determine the 'burst' of activities. Larger the values, longer will be the dance but intervals between will also be longer and vice versa.
5. Based on the different values, make different prototypes.
Things to watch out for:
1. A lot of vibration will accompany the robotic movements. You can use the rubbery offset used in old CD walkmans to offset the same here.
2. Be careful while using the soldering iron. It generates temperatures in excess of 180 degree centigrade and may cause serious burns.
3. It is important that the solar panels are able to supply a voltage greater than the voltage at which the 1381 part triggers.
4. The robot will function only in light. It may not work well in flashlight. But try it out definitely.
 source: www.greendiary.com

tags: solar powered, solar power

Telephone Ring Indicator and Line

Telephone Line Ring and Indicator

It is a relatively simple circuit, which can have visual and audible indication when we telephone gradients on the phone line. Calls to the line, converted into pulses of frequency 400 Hz from the IC2, the output 3. Then through IC4, as reinforced by two times, can lead to an input amplifier and a speaker to hear the slope, at which level we want. The desired sound level is adjusted by the trimmer TR1 that if we can be replaced with a potentiometers. With the passage Led LD1 have visual indication of the slopes. Simultaneously through the IC3 may be driving an external circuit, adapted to the needs of each user.

Part List

R1-3-13=4.7Kohm	C1-7 =100nF 630V	Q1-2 = BC550C
R2-11-12 =1Mohm	C2=4.7nF 63V MKT	IC1-3 =4N35 - CNX38
R4 =1Kohm	C3 =220uF 25V	IC2=LM555
R5 = 2.2Kohm	C4 =33nF 63V MKT	IC4 =TL071
R6 = 33Kohm	C5 =220nF 63V MKT	LD1 =LED 3-5 mm
R7 =390Kohm	C6 =10uF 25V	TR1=10Kohm Trimmer or Pont.
R8 =820ohm	C8 =47nF 63V MKT	CON1 =4 pin connector
R9 =22Kohm	C9 =100uF 25V	CON2 =4 pin connector
R10 =1.8Kohm	D1-2 =20V 1,3W Zener
R14 =10Kohm	D3 =1N4002

Source: http://users.otenet.gr/~athsam%20/telephone_ringer.htm