1. ACCURATE ELECTRONIC STOPWATCH
PROJECT GUIDE
V.MANOHAR
SUBMITTED BY :
CH.SHRUTHI(09871A0425)
B.SANTHOSH KUMAR(09871A0421)
Assoc.prof

2. INTRODUCTION
Stopwatches find use as time keeping devices in many fields, namely sports. Stopwatches may be analog or digital. Digital stopwatches are much more common the analog version owing to their higher accuracy and ease of use.
Here we have tried to realize a digital stopwatch of reasonable accuracy and reliability.

3. COMPONENTS REQUIRED IC 7490 (Decade counter)
IC (Dual Decade counter)
IC 74C926 (4 Digit counter with multiplexed 7segment LED driver)
BC547 Transistors
Resistors
Capacitor
1Mhz Crystal
Switches

4. CIRCUIT DAIGRAAM

5. IC 7490 (DECADE COUNTER)

6. IC 7490 Specifications
Supply Voltage Vcc 7.0v
Input Voltage Vin -0.5 to 7.0
Input Current Iin -30 to +1 mA
Output Voltage Vout -0.5 to +Vcc V
Operating free Air Temp Ta 0 to 70 C

7. Dual decade (0-9) ripple counter
The contains two separate decade (0 to 9) counters, one on each side of the chip. They are ripple counters so beware that glitches may occur in any logic gate systems connected to their outputs due to the slight delay before the later counter outputs respond to a clock pulse.

8. IC 74390 SPECIFICATIONS Supply Voltage Vcc 4.75 to 5.25 V
High Level Current -400 µA
Low Level Current 8 mA
Operating Free Air Temperature 0 to 70
Dimension : 16cm ¡Ñ11cm ¡Ñ4.5cm
Weight : 0.34kgs
Altitude : up to 5000m

9. TRANSISTOR (BC 547)
BC547 is an NPN bi-polar junction transistor. A transistor, stands for transfer of resistance, is commonly used to amplify current. A small current at its base controls a larger current at collector & emitter terminals.
BC547 is mainly used for amplification and switching purposes. It has a maximum current gain of 800. Its equivalent transistors are BC548 and BC549.

10. Specifications Collector – Emitter Voltage VCEO 45 Vdc
Collector – Base Voltage VCBO 50 Vdc
Emitter – Base Voltage VEBO 6.0 Vdc
Collector Current — Continuous IC 100 mAdc
Operating and Storage Junction Temperature Range – 55 to +150 °C

11. RESISTORS
A resistor is a component of an electrical circuit that resists the flow of electrical current.
A resistor has two terminals across which electricity must pass, and is designed to drop the voltage of the current as it flows from one terminal to the next.

12. 7 SEGMENT DISPLAY (LTS 543)

13. In a simple LED package, typically all of the cathodes (negative terminals) or all of the anodes (positive terminals) of the segment LEDs are connected and brought out to a common pin

14. Quieries ?

15. THANK YOU