Servo Motor Tester Circuit

This circuit allows you to isolate the servo motor from the project circuit and feed it with pulses of varying width nd checking the angle that the servo motor turns to. the circuit is built using two NE555 IC's and a few discrete components. IC1 is set as an astable multivibrator with a time period of 20 ms. Every 20 ms, the astable provides a very sharp negative pulse to trigger IC2. Timer IC2 is configured as a monostable multivibrator that produces 1ms, 1.5ms and 2ms long pulses to rotate the servo motor (M1). 

Simple Adjustable DC - DC Converter

It's easier to generate DC from AC mains supply using a transforme and some diodes but the difficult part comes when we need to regulate the supply to feed sensitive devices such as mobile phones. Here's a versatile DC to DC coupler that 'll give you regulated fixed dc output voltages like 5V to charge mobile phone, 12V for external hard drives etc. You may use a 19V laptop adapter to route various voltages such as 5V , 6V, 12V from it.

Simple Laptop Audio Amplifier Circuit

When it comes to laptop sounding, most of the laptops currently in the market has very low sound output (laptops like DELL XPS is an exception). If you need more powerful sound, you need to amplify the sound output from the laptop. Here's a simple amplifier circuit making use of the SANYO LA4440 IC which is ideal for low power audio applications because it gives better sound clarity and less distortion.

Laptop audio amplifier circuit

Fortunately the circuit diagram is very simple and even a beginner can assemble and debug it. The circuit is built around the previously mentioned LA444o IC and a few components. The amplifier is a dual channel one with 6W for each channel. So a 10 W speaker would be very sufficient. Connect pins 2, 6 and ground of IC1 to the stereo jack which is to be used with the laptop.

1Hz Clock Generator Circuit Using COB

Let's familiarize with a COB - chip on board device by building a precision 1Hz clock generator. Circuits that usually generate 1Hz clock makes use of ICs with variable capacitors but they are not very precise. ( micro controller based one should be precise but it costs large ). better accuracy can be obtained by a COB found inside a digital clock, which is cheaply available in the market.

Visitor Alarm Secret Bell

This circuit can acts as a visitors alarm as well as a secret bell which can be used to identify family members. If you'e living in flats, it'll become necessary to verify the visitor before opening the door. This circuit senses single puff of breath and activates a musical bell automatically.

LED Running Display Using NE555

Here's a circuit to build a led based running display using easily available general purpose timer IC NE555 and a popular decade counter IC CD4017. This display consist of 24 LED's of four layers. The NE555 is wired as an astable multivibrator whose output triggers CD4017 counter.

Dual power supply from single battery supply

Dual power supply is a very essential part in the laboratory or in your work while there you use op-amps in your circuit. Most of the opamp Ic's require dual voltage supply. But it's difficult to provide dual power supply as it's costlier than a single battery.