The parallel port of the PC is a powerful platform for implementing projects dealing with the control of real-world peripherals. It can be used to control home and other electronic appliances. The computer program through the interface circuit controls the relays, which, in turn, switch the appliances ‘on’ or ‘off.’
RFID technology is used in vehicle parking systems of malls and buildings (refer Fig. 1). The system normally consists of a vehicle counter, sensors, display board, gate controller, RFID tags and RFID reader. Presented here is an automatic vehicle parking system using AT89S52 microcontroller.
Moving-message displays are ideal to get your message (advertisements, greetings, etc) across in an eye-catching way. You can make an LCD show a brief moving message by interfacing it to a microcontroller.
A charge controller is one of the main components of a solar battery charging system . Its main function is to fully charge a battery without permitting overcharge or reverse current flow (generally during night). If a solar array is connected to a lead-acid battery with no overcharge protection, the battery life is adversely affected.
The circuit uses a dual-timer IC LM556 (IC1) and penta-watt audio power IC TDA2003 (IC2) (refer Fig. 1). Both the timers of LM556 are wired as astable oscillators to generate square waves. The first timer is configured to generate a 400Hz audible tone and the second timer for a 550Hz tone.
The circuit (refer Fig.1) is built around transformer X1, a standard bar magnet, reed switch S2, timer IC NE555 (IC1), opto-coupler IC MOC3020 (IC2), TRIAC BT136 and a few discrete components. Timer IC1 is wired as an astable multi-vibrator whose reset pin 4 is controlled by the reed switch. The reed switch fitted in the door frame acts as the sensor. A magnet is fixed on the door panel close to the reed switch.
This circuit provides constant-current charging for batteries like nickel-cadmium (Ni-Cd), nickel-metal hydride (Ni-MH) and lithium-ion (Li-ion). The charger maintains constant current flow by using the property of the transistor that allows the current through the collector to be almost equal to the current through the emitter.
Here you can find out how to drive an led matrix with 64 LEDs (8 rows by 8 columns - 8x8 display) or less e.g. 35 LEDs (7 rows by 5 columns - 5x7 dot matrix). This is an easy DIY project which uses persistence of vision to let you drive the 64 led matrix with only 10 microcontroller outputs.
Measurement of peak level is useful while testing an amplifier or a similar device. It is handy while testing a logic circuit, as it can pick up a high transient pulse (or show that there is none) and measure an output that is swinging strongly in both directions.
This handy, pocket-size mobile transmission detector can sense the presence of an activated mobile phone from a distance of one and a-half metres. So it can be used to prevent use of mobile phones in examination halls, confidential rooms, etc. It is also useful for detecting the use of mobile phone for spying and unauthorised video transmission.
Here is a system based on PIR motion detector module BS1600 (or BS1700) that can be used for security or corridor lighting in power-saving mode. The working of the circuit is simple. When you power-on the circuit after assembling all the components including the CFL, the CFL will glow for 10 seconds, turn off for 30 seconds, glow for 10 seconds and then turn off. Now the circuit is ready to work.