Hardware Based Projects

We have designed and implemented a microcontroller-based system that can measure the temperature from 20 degree centigrade to 100 degree centigrade. Our main objective is to make a digital thermometer that will show temperature in LCD display using the value of output voltage that changes depending on the value of thermistor. LCD display will show digital value of temperature as the change of output voltage become digital. To implement this system at first, we calibrated the thermistor’s resistance with different value of temperature within 5-degree centigrade temperature interval. Then, an equation was formed using those value using Excel. After that, using that equation, microcontroller was designed and tested for accuracy varying the temperature and comparing with the actual temperature on analog thermometer. In this project, we got average error of 3.46%.

This project is based on a circuit that can amplify an audio signal that is given by microphone. This circuit can be used as small mic and loudspeaker system.Here we used an LM324 op-amp. In this IC pin1 is output to its inverting and 2 is non-inverting pin. Pin 4 goes +Vcc and pin no. 11 goes to ground. In pin 3 we set a reference Voltage by using a variable resistor. We use pin2 or inverting terminal as an input through microphone. We use capacitor to avoid noise and use 1k resistor or Voltage drop at pin2.We use Rf feedback circuit connected with pin2 and pin1 for better amplify the input signal. After amplifying the signal through feedback circuit the output signal is again filtered by using capacitor. Here we use Darlington Cascade system for better current rating. Because in IC op-amp input resistance is very high so output current is quite small. So we can’t get sufficient current rating at output terminal. For getting better current rating, we use two transistor as cascaded. We use a 1k resistor for Voltage drop of base terminal .In this way we get amplified output signal.

The RF module comprises of a RF Transmitter and a RF Receiver. The transmitter and receiver pair operates at a frequency of 433 MHz An RF transmitter receives serial data transmits it wirelessly through radio frequency through its antenna connected at pin 4. The transmission occurs at the rate of 1Kbps-10Kbps. The transmitted data is received by an RF receiver operating at the same frequency as that of the transmitter. In this RF system, digital data is represented as variations in the amplitude of carrier wave which is known as Amplitude Shift Keying (ASK). The transmitter draws no power when transmitting logic zero while fully suppressing the center frequency. When logic one is sent carrier is fully on to about 4.5 mA. The RF module used here along with a pair of encoder/decoder. The encoder is used for encoding parallel data for transmission feed while reception is decoded by a decoder. A 750-kilo ohm resistor is connected between the oscillator terminals of encoder IC to enable the oscillator. Similarly, a 33K ohm resistor is connected between the oscillator pins of the decoder.

Our main objective is to make a digital lux meter that will show intensity of light in LCD display using the value of output voltage that changes depending on the value of thermistor. LCD display will show digital value of intensity of light as the change of output voltage become digital. we have taken output from series combination of 10k resistor and LDR. With increasing the intensity of light, the value of LDR increases so that the output value will be decreased and vice versa. Finally, the output voltage will be converted into digital value (0-1023). We have compared the data we got using analog Lux meter and our project output and found average 15% error. Because the analog lux meter was very fluctuating when we were taking data. Also, the light system was not very good.