Description.

Here is a simple circuit that will give a visual indication when the soil water level inside your flower pot goes low below a certain limit.

The U1C and associated components are wired as an oscillator producing a 2KHz square wave. This square wave is given to one gate input of U1D via a variable potential divider former by R1 and R2.When the resistance across the probes A and B are low that is when soil moisture level is high, the C2 will divert the square wave to ground. The output of U1D will be high. The U1 A inverts this high state to low and so the IC U1B is blocked from producing oscillations. The LED will remain OFF. When there is no moisture across the probes, the C2 cannot bypass the 2KHz signal to the ground and it appears at the gate input of U1D.The output of U1D goes low, and it is inverted to high by U1A.The oscillator wired around U1B is activated and it starts oscillating. These oscillations are amplified by Q1 to drive the LED and LED starts pulsating as an indication of low moisture. Since square wave is used there won’t be any oxidation on the probes. The resistor R7 limits the current through LED and ensures a longer battery life.

Circuit diagram with Parts list.

Notes.

• Power the circuit from a 3V battery.
• Two metal wires 10 cm long and 5cm apart driven into the soil will do the job for probes.
• The probes are to be connected at the terminals A and B shown in circuit.
• Capacitors C1 and C2 must be polyester type.
• The IC U1 is a quad two input Schmitt NAND IC 4093.
• The sensitivity can be adjusted by varying the preset R2.
• Mount the IC on a holder.

Description.
This is a very simple yet effective circuit in which the equipments connected at the so called trailing sockets will run only if the equipment connected at the control socket is switched on. For example, let’s connect a motor is connected to the control socket and a lamp is connected at the trailing socket. The lamp will glow only when the motor is running.

When the load connected at the control circuit is switched on, the load current flows through the diodes and as a result there will a voltage drop across the diodes. This voltage drop is sufficient enough to switch on the sensitive triac T1 and the equipments connected at the trailing sockets gets power supply. The components R2 and C1 forms a snubber circuit which protects the triac from transient fluctuations.

Almost all equipments like motors, drills, blenders, fan, old TV, radio, amplifiers etc can be connected at the control socket. In case of modern TV, computers, amplifiers, etc the power switch does not completely isolate the equipment and the equipment will draw a small amount of current in the standby mode which is sufficient enough to trigger the triac . Such equipments cannot be used on the control socket because it makes the trailing equipments ON even if the control equipment is OFF.

Circuit diagram with Parts list.

Notes.

• Assemble the circuit on a good quality PCB.
• The triac T1 must be a 600V, 8A, high sensitive gate type like TIC 225M.
• Maxim load that can be connected at the trailing socket is 1000W.
• Fit the triac with a heat sink.
• Take at most care while handling this circuit as it is connected to 230V AC.

SONY-The name speaks “Quality” and VAIO speaks “Brand”. I am using this notebook for the last one year and am more than satisfied with its performance. Sony Vaio VGN CR36 is an awesome model with a simple but hot design and cool performance.

Specifications-Vaio VGN CR36

Processor- Intel Core 2 Duo-T8100-2.10Ghz

Memory - 2GB

HDD - 200GB

Display – 14.1″ WXGA Display-Clear Bright LCD Lite

OS – Windows Vista Home Premium

Optical Drive – SONY DVD RW

Additionals

1. 1.3 MP camera with Original picture frame

2. Hot Keys for Multimedia

3. Hot Keys for Camera, Sound, Display, AV mode

4. WiFi enabled with external switch

5. Finger print Sensor

6. 256MB ATI Radeon Graphics card

7. User friendly Keyboard and Touch pad

8. Illumination for user actions

9. 6 cell Li-Fe battery with 4 hrs backup life

10. Sony-Stereo speakers

Review

Well, a great model worth its price as Vaio represents both quality and brand. I am convinced with its reliability and ruggedness. My professional life involves lots of travels that too in bikes. Withstanding such rough conditions is highly demanding. So as a 1st note Sony is really successful in keeping its model survive rough conditions. Second point that I should make out is its Display Quality! Watching movies in your Sony Vaio CR 36 is a different experience, with headphones in your ear you will rock! Stere0 speakers are just OK, but watching movies with headphones is a different experience. Next is the cool-user friendly keyboard which allows faster typing and gentleness to fingers. Hot keys are really really useful especially the mute button and play/pause button. A motion eye 1.3 mega pixel web cam serves better in video chatting. Finger print sensor allows greater secuirity locking features. Moreover the performance of this notebook with 2GB memmory and T8100 Core2Duo is simply amazing!

Competitor model: Dell XPS M 133o

Rating: 4/5

Recommended: For medium sized professionals like Team leaders, Young startups, Managers etc. especially the Black colored one. Pink/Red/Golden models of same are available as VGN CR 35 for ladies and girls.

Gallery

Description.

This is a simple, but very useful circuit that can be used to transmit telephone conversations. When the telephone receiver is on hook the voltage across the lines will be about 48 volts. The preset R7 is so adjusted to obtain a 24.7 V across between the cathode of D2 and ground. At this voltage the Zener diode D2 will be in breakdown and the transistor T1 will conduct. This makes the transistor T2 OFF. When the receiver is off hook, the line voltage drops to about 11 volts. This makes the transistor T1 OFF and subsequently the T2 ON. The T2 in switched ON condition will provide a DC path for the transistor T3 used in the FM transmitter section.

The transistor T3 is wired as a common emitter radio frequency oscillator. In simple words the transistor T2 serves as an ON/OFF switch for this oscillator. The modulated signal will be available at the collector of transistor T3 and the signal id fed to the antenna via capacitor C5.

Circuit diagram with Parts list.

Notes.

• Assemble the circuit on a good quality PCB.
• For L1 make 45 turns of 36 SWG enameled copper wire on the resistor R6 itself.
• The resistor R6 must be a 1M, 1 watt resistor.
• For L2 make 3 turns of 21 SWG enameled copper wire on a 12 mm plastic former.
• For antenna, use a 1 meter insulated copper wire.
• The capacitor C3 can be a 50pF trimmer.

Description.

Here is the circuit diagram of an easy to build long range AM transmitter circuit based on three transistors.With correct tuning and a matching antenna, the transmitter can deliver signals up to a distance of 2 kilometers.

The audio signal to be transmitted is given to the base of the transistor Q1 via the audio driver transformer T1.The modulated signal is developed at the collector of transistor Q1.The frequency of the transmitted signal can be tuned adjusting the gang condenser C7.The required amplification of the modulated signal is done by the two transistors Q2 and Q3.The  two  transistor amplifier stages are connected in parallel for obtaining maximum power. The signal to be transmitted is coupled to the antenna via the capacitor C4.

Circuit diagram with Parts list.

Notes.

• The inductor L1 can be made by making 56 turns of 365 WG enameled copper wire on a 1 cm former.
• The transformer T1 can be a general purpose audio driver transformer seen in transistor radios.
• Inductor L2 can be a 10 mH general purpose radio frequency choke.
• Use a 1 meter insulated copper wire as antenna.
• The circuit can be powered from a 9V PP3 battery.
• Adjust the value of C7 for maximum range.
• Also, you can experiment with the length of antenna for maximum range.
• The resonator F1 used here is a two terminal type without a ground pin. If you are using a three terminal one, the ground pin must be connected to the circuit’s ground.