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.