High Intensity Energy Efficient LED Light

Here is a rechargeable LED lamp that gives you bright light for a long duration of time as it consumes little power. The circuit presented here is compact, automatic, reliable, low-cost and easy to assemble.

The circuit comprises power supply, battery charging and switching sections. The power supply section takes power from 230V AC mains supply without using a transformer. Capacitor C1 is used as an AC voltage dropper, a well-known transformerless solution. This helps to make the circuit compact without generating heat, as capacitor C1 dissipates negligible power. Capacitor C1 also protects against fluctuations in mains.

Cellphone Operated Land Rover

Conventionally, wireless-controlled robots use RF circuits, which have the drawbacks of limited working range, limited frequency range and limited control. Use of a mobile phone for robotic control can overcome these limitations. It provides the advantages of robust control, working range as large as the coverage area of the service provider,no interference with other controllers and up to twelve controls.

Remote Controlled 6-Camera CCTV Switcher

Closed-circuit television (CCTV) uses video cameras to transmit signals to specific monitors. It differs from broadcast television in that the signal is not openly transmitted, though it may employ point-to-point wireless links. CCTV is often used for surveillance in areas that need security,such as banks, casinos, shops, departmental stores and airports or military installations. 
Here is a remote-controlled CCTV switcher circuit to monitor six cameras on a single or dual monitor/TV. 

Smart Voltage Stabilizer Using PIC16F877A

Voltage stabilizers are used for many appliances in homes, offices and industries. The mains supply suffers from large voltage drops due to losses on the distribution lines en route. A voltage stabilizer maintains the voltage to the appliance at the nominal value of around 220 volts even if the input mains fluctuates over a wide range.

Water Level Controller and motor Protector

Many a time we forget to switch off the motor pushing water into the overhead tank (OHT) in our households. As a result, water keeps overflowing until we notice the overflow and switch the pump off. As the OHT is usually kept on the topmost floor, it is cumbersome to go up frequently to check the water level in the OHT.

Over/Under Voltage Cut-off with On-Time Delay

Here is an inexpensive auto cutoff circuit, which is fabricated using transistors and other discrete components. It can be used to protect loads such as refrigerator, TV, and VCR from undesirable over and under line voltages, as well as surges caused due to sudden failure/resumption of mains power supply. This circuit can be used directly as a standalone circuit between the mains supply and the load, or it may be inserted between an existing automatic/manual stabilizer and the load. 

Parallel Port Logic Analyzer

When you build a digital electronic project and have trouble with it you need a device to debug it. To analyze logic output from your project you need a Logic Analyzer. 
If you don’t have it you can try to build by yourself cheap logic analyzer device using parallel port. The device only use few resistors and IC 74HC245 as data buffer. To display the graphical output from logic analyzer device you can use Fabulous Logic Analyzer software, here.


Schematic:

Parallel Port logic analyzer

Component Required:
IC1,               74HC245
R1-R8,         10K ohm
R9-R16,       100 ohm
R17,              2K ohm
LED
DB25 Male, Parallel Port Connector

Telephone Operated Remote Control v2 Using PIC16F876A

This is a newer version of previous device. This one can have up to 6 relays and 6 sensor-state inputs.
The task was to build a device that connects to the phone line and has a relay as an output switch. It should also sense if the connected «consumer» is turned-on or off and report to the administrator at the other end of the phone line. The administrator would then call-in the device, log in with the password, and check the state of «consumer», turn it on or off, change password or some other settings.


Download: Schematic, Program files And Documentation


Schematic:

Full Schematic

Telephone operated remote control

Telephone Operated Remote Control Using PIC16F84A

This design controls up to 8 devices using a PIC microcontroller (PIC16F84A) connected to the phone line. The unique feature here is that unlike other telephone line based remote control, this device does not need the call to be answered at the remote end so the call will not be charged. This device depends on number of rings given on the telephone line to activate/deactivate devices.